Saturday, February 9, 2008
Global Positioning System
The Global Positioning System (abbreviated in GPS, in its turn abbreviation of NAVSTAR GPS, acronym of NAVigation System Time And Ranging Global Position System), is a positioning system on base to satellitare, to total cover and continues, managed from the department of the American defense.
History of the GPS
In the 1991 the USA opened to the world the service with name SPS (Standard Positioning System), with detailed lists differentiated that called soldier PPS (Precision Positioning System). In practical it came introduced the so-called Selective Availability (KNOWS) that it introduced intentional errors in marks them satellitari in order to reduce the accuracy of the survey, concurring precisions single in the order of 100-150 m.
The GPS has been created in substitution of the previous system, the Transit, when the USA, rinunciando to the Selective Availability, have rendered the first one taken care of how much the second, supporting it with a net of 24 satellites crafts them.
The degradation of marks them has been disabilitata from the month of May 2000, thanks to a decree of the President of the United States Bill Clinton, putting therefore to disposition the precision puts into effect them of approximately 10-20 m. In the models for civil use a device is present that inhibits the operation to heights and advanced speeds to sure values, in order to prevent of the assembly on unexpected missiles.
The UE has in plan the completion of an own net of satellites, Sistema of Galileo positioning, for civil scopes, between which the GPS. This plan has an obvious strategic valence in how much the net American is property of the single United states and is managed military authorities, than, in particular conditions, they could decide discretionarily and unilaterally to reduce the precision or block the access selective to the system; the sharing of the investment and the property from part of the utilizzatori states guarantees continuity, accessibility and interoperabilità of the service.
The GPS has been created in substitution of the previous system, the Transit, when the USA, rinunciando to the Selective Availability, have rendered the first one taken care of how much the second, supporting it with a net of 24 satellites crafts them.
The degradation of marks them has been disabilitata from the month of May 2000, thanks to a decree of the President of the United States Bill Clinton, putting therefore to disposition the precision puts into effect them of approximately 10-20 m. In the models for civil use a device is present that inhibits the operation to heights and advanced speeds to sure values, in order to prevent of the assembly on unexpected missiles.
The UE has in plan the completion of an own net of satellites, Sistema of Galileo positioning, for civil scopes, between which the GPS. This plan has an obvious strategic valence in how much the net American is property of the single United states and is managed military authorities, than, in particular conditions, they could decide discretionarily and unilaterally to reduce the precision or block the access selective to the system; the sharing of the investment and the property from part of the utilizzatori states guarantees continuity, accessibility and interoperabilità of the service.
Satellites
They are disposed on 6 orbital plans tilts to you of 55° regarding the equatorial plan (therefore do not cover the polar zones) to shape of ellipses to low eccentricity. Every slowly orbital it has 3 or 4 satellites, and the plans are disposed in such way that every utilizzatore on the earth can receive marks them at least 5 satellites. Their quota is of 20 200 km. Every satellite emits on derived the 1,5 frequencies of 1,2 and GHz from an only oscillator to high stability. The scope of the double frequency is that one to eliminate the error which had to the atmospheric refraction. On these carrying frequencies, modulated in phase, come emitted the messages of ephemeris, everyone of the durations of two minuteren; they begin and finish entire to the equal minuteren of the GMT. These messages of ephemeris contain mark them hour and the orbital parameters of the satellite.
In such a way receiver GPS, while he carries out conteggio the Doppler, receives the parameters of the orbit from which drift the position of the satellite: he comes therefore to arrange of all the elements necessary to define in the space the position surface.
In such a way receiver GPS, while he carries out conteggio the Doppler, receives the parameters of the orbit from which drift the position of the satellite: he comes therefore to arrange of all the elements necessary to define in the space the position surface.
Stations of tracciamento and center of calculation
The tracciamento of the satellites comprises all those operations apt to determine the parameters of the orbit. To that they exactly supply 4 master stations said of tracciamento (main tracking stations) and a calculation center (computing center), all situate to you in USA territory, and in particular to Wahiova (Hawaii), Point Mogu (California), Prospect Harbur (Maine) and Rosemount (Minnesota). Point Mogu is also center of the calculation center. Every time that every satellite in its orbital motion flies over the territory American the tracciamento stations of it records the Doppler data that they come starts you on the calculation center and here values you for the determination of the orbital parameters. In order to resolve this problem it has been necessary to come in possession of a faithful mathematical model of the land gravitational field. The construction of this model has been one of the problems more arduous solution in the development of the Transit plan from which it is derived puts into effect it them Navstar. It turns out you of this surveying on the land gravitational field, that they are of immense capacity from the geodetic point of view, can be reassumed in an image of the globe in which they come brought back the lines of equal scostamento of Geoide (LMM) fromthe ellissoide of reference APL.
Stations of soccorrimento
The orbital parameters of every satellite, as soon as it determines to you near the calculation center, are re-united in a message that comes forwarded to the satellite interested by means of one of the soccorrimento stations. The satellite records the parameters receipts in its memory and them reirradia to the customers.
Receiver GPS
The operation principle is based on a method of spherical positioning, that the time employed consists in measuring from marks them radio to cover the distance satellite-receiver. Knowing the time employed from it marks them in order to reach the receiver and the exact position at least 3 satellites for having a position 2D (bidimensional), and 4 for having a position 3D (three-dimensional), is possible to determine the position in the space of the same receiver. Such procedure, called trilaterazione, uses alone distance information and is similar to the triangolation, from which however the angles differ for the fact to make less than regarding information.
The precision can ulteriorly be increased thanks to the use of systems like WAAS (American) orthe EGNOS (European), perfectly compatible between of they. They consist one or two in geostazionari satellites that they send of marks them of correction. The modality Differential-GPS (DGPS) uses a connection radio in order to receive given to DGPS from one earth station and to obtain an error on the position of a pair of meters. Modality DGPS-IP takes advantage of, rather than radio waves, the Internet net for the shipment of correction information.
Receivers GPS ("external"), interfacciabili by means of door USB or logons without threads like the Bluetooth exist in commerce, that they concur to realize navigators GPS on several devices you: portable palmari, PC, computers, and, if it equips you of sufficient memory, also cellular telephones. For navigation they exist software I affixed to you, owners or open source that they use one cartography, anch' it publishes or owner.
The precision can ulteriorly be increased thanks to the use of systems like WAAS (American) orthe EGNOS (European), perfectly compatible between of they. They consist one or two in geostazionari satellites that they send of marks them of correction. The modality Differential-GPS (DGPS) uses a connection radio in order to receive given to DGPS from one earth station and to obtain an error on the position of a pair of meters. Modality DGPS-IP takes advantage of, rather than radio waves, the Internet net for the shipment of correction information.
Receivers GPS ("external"), interfacciabili by means of door USB or logons without threads like the Bluetooth exist in commerce, that they concur to realize navigators GPS on several devices you: portable palmari, PC, computers, and, if it equips you of sufficient memory, also cellular telephones. For navigation they exist software I affixed to you, owners or open source that they use one cartography, anch' it publishes or owner.
GPS and Theory of the Relativity
The satellitari clocks are affections from the consequences of the Theory of the Relativity. In fact, because of the effects arrange you of the relative speed, that the time slows down on the satellite of approximately 7 microsecond ones to the day, and of the smaller curving of the spaziotempo to level of the orbit of the satellite, than it accelerates it of 45 microsecond ones, the time on the satellite slides to a leggermente faster rhythm that to earth, causing an advance payment of approximately 38 microsecond ones to the day, and rendering necessary one automatic correction from part of the edge electronics. This observation supplies an ulterior test of the exactitude of the theory in an application of the real world. The found relativistico effect is in fact exactly correspondent to that calculable one theoretically, at least in the supplied limits of accuracy from the instruments of measure currently available.
The GPS in I use daily paper
Modern receivers GPS have caught up of the costs many contents. After the cellular telephone we are assisting to the spread of a new one cult: that one of the navigator to satellitare personal. The market by now offers to solutions to low cost for all employs it and all the pockets that are not only revealed effective for navigation to satellitare in himself and himself, but also for civil uses, for the monitoring of the services you furnish and for the control of the territory. Several solutions exist:
* Integrated: they are devices portable you All-in-One that they incorporate a receiver GPS, display a LCD, a loudspeaker, the processore who executes the instructions, dates usually from an operating system owner, one slot for memory cards where memorizzare the cartography.
* Hybrid: they are devices portable you (PC, Palmari, SmartPhone) that, been born for various, rendesi scopes they are adapted to navigation to satellitare through the connection of an external receiver GPS (Bluetooth or via cable) and the adoption of a dedicated software, in a position to managing the cartography.
With the capillary spread of systems GPS, and the consequent discouragement of the costs of the receivers, many producers of cellular telephones have tried to insert a module GPS to the inside of their products, opening themselves therefore to the new market of services LBS (Location Services Base, services base to you on the positioning). Such services come more and more take advantage of in order to offer to you also on web of the services the many profits. However, the relative slowness with which GPS finishes them acquires the own position at the moment of the ignition (in average, between the 45 and 90 second ones), due to the necessity to try the satellites in sight, and consequent the remarkable engagement of energetic resources hardware and, has refrained at first this type of coupling. In the last years, but, it has been introduced in this type of telephones the system Assisted GPS, saying also "A-GPS", with which it is possible to obviate to such problems: they are made to reach finishes them GPS, through the net of mobile telephony, the information on the visible satellites from the cell to which the customer it is coupled. In this way a telephone A-GPS can in little second ones gain the own position begins them, in how much is assumed that the satellites in sight from the cell are same the visible ones from finish them under its cover radio. Such system is much profit also like emergency service, as an example in order to localize means or wounded persons later on to an incident.
* Integrated: they are devices portable you All-in-One that they incorporate a receiver GPS, display a LCD, a loudspeaker, the processore who executes the instructions, dates usually from an operating system owner, one slot for memory cards where memorizzare the cartography.
* Hybrid: they are devices portable you (PC, Palmari, SmartPhone) that, been born for various, rendesi scopes they are adapted to navigation to satellitare through the connection of an external receiver GPS (Bluetooth or via cable) and the adoption of a dedicated software, in a position to managing the cartography.
With the capillary spread of systems GPS, and the consequent discouragement of the costs of the receivers, many producers of cellular telephones have tried to insert a module GPS to the inside of their products, opening themselves therefore to the new market of services LBS (Location Services Base, services base to you on the positioning). Such services come more and more take advantage of in order to offer to you also on web of the services the many profits. However, the relative slowness with which GPS finishes them acquires the own position at the moment of the ignition (in average, between the 45 and 90 second ones), due to the necessity to try the satellites in sight, and consequent the remarkable engagement of energetic resources hardware and, has refrained at first this type of coupling. In the last years, but, it has been introduced in this type of telephones the system Assisted GPS, saying also "A-GPS", with which it is possible to obviate to such problems: they are made to reach finishes them GPS, through the net of mobile telephony, the information on the visible satellites from the cell to which the customer it is coupled. In this way a telephone A-GPS can in little second ones gain the own position begins them, in how much is assumed that the satellites in sight from the cell are same the visible ones from finish them under its cover radio. Such system is much profit also like emergency service, as an example in order to localize means or wounded persons later on to an incident.
Cartography and open source
The laws on the tutelano copyright the cartographic works and second preview the payment of royalties the dispositions of their authors. Between the most complete surveys of the Italian territory the papers of Military Navy and situated of Italian Atlas (the official reference of the national cartography re-enter). The material is available free of charge for Public Administration, and to payment for the citizens.
In the United States the national cartography is not covered from copyright and that has favorite the spread of the interactive maps with services which maps.google.com and earth.google.com. The sevizio of google it is subject to payment for I use it of the paper beyond a sure level of zoom, in order to visualize enterprises or other agencies.
A free cartography has been able to extend also to areas of the territory that do not correspond to large agglomerate city or tourist zones to you, places for which little customers would use the consultation service.
In Europe, a cartography "owner" is not material usable for distributions open source that they must trace one new cartography without to use the existing material. They exist software (in particular applet java) in a position to acquiring a geographic paper in jpeg and supplying base services as interactive navigation and the calculation of the optimal distance. However, a private use therefore as a public distribution of these services is subject to the law of the copyright.
In the surveys it still lacks a standard formattazione of the cartography for which they are used you form you of vectorial diagram or forms to you raster; between those of vectorial diagram the extension jpeg on which is diffused mainly is estimated and traced the optimal distances. Less diffuse they are other you form you of vectorial diagram that concurs also to define metadati with which the customer can personalize the papers with important information for he. The software of conversion between the several one often forms to you is programs to payment.
Between the greater plans of a software open source for navigation to satellitare (alternative to the diffuse Tom Tom and others), it is from noticing that the Roadster plan concurs to define of the metadati ones regarding the GPS_Drive plan.
In the United States the national cartography is not covered from copyright and that has favorite the spread of the interactive maps with services which maps.google.com and earth.google.com. The sevizio of google it is subject to payment for I use it of the paper beyond a sure level of zoom, in order to visualize enterprises or other agencies.
A free cartography has been able to extend also to areas of the territory that do not correspond to large agglomerate city or tourist zones to you, places for which little customers would use the consultation service.
In Europe, a cartography "owner" is not material usable for distributions open source that they must trace one new cartography without to use the existing material. They exist software (in particular applet java) in a position to acquiring a geographic paper in jpeg and supplying base services as interactive navigation and the calculation of the optimal distance. However, a private use therefore as a public distribution of these services is subject to the law of the copyright.
In the surveys it still lacks a standard formattazione of the cartography for which they are used you form you of vectorial diagram or forms to you raster; between those of vectorial diagram the extension jpeg on which is diffused mainly is estimated and traced the optimal distances. Less diffuse they are other you form you of vectorial diagram that concurs also to define metadati with which the customer can personalize the papers with important information for he. The software of conversion between the several one often forms to you is programs to payment.
Between the greater plans of a software open source for navigation to satellitare (alternative to the diffuse Tom Tom and others), it is from noticing that the Roadster plan concurs to define of the metadati ones regarding the GPS_Drive plan.
Cartography
The cartography is with of scientific, technical and artistic acquaintances finalized to the symbolic but veritiera rappresentazione of geographic information - or demographic, economic, political, culturalstatistics , however in relation to the geographic place in which they are come true - on supports plans (geographic papers) or spherical (globes).
The geometric or mathematical techniques that transform the expressed points in geographic coordinates in points expressed in cartesian coordinates call cartographic projections.
The cartographic studies and the relative applications in the various fields applied to you have been rivoluzionate from the development and the spread of Sistemi Informed to you Geographic (GIS).
The first one to make a paper of the Mediterranean was Dicearco from Messina, that it devised a system based on two orthogonal main lines on which a reticulum of squares was developed.
The geometric or mathematical techniques that transform the expressed points in geographic coordinates in points expressed in cartesian coordinates call cartographic projections.
The cartographic studies and the relative applications in the various fields applied to you have been rivoluzionate from the development and the spread of Sistemi Informed to you Geographic (GIS).
The first one to make a paper of the Mediterranean was Dicearco from Messina, that it devised a system based on two orthogonal main lines on which a reticulum of squares was developed.
Changes of the celestial coordinates
Because of the movements in the long term of the Earth (first of all that one known with the precession name of the equinoxes), the stars do not have celestial coordinates of all the fixed ones but they are moved with the time. This movement is independent from the motion just of the stars, because draft of a movement of the observer rather than of the star. To eye knot and on scales of little years he is imperceptible, but for the astronomical observations the problem is placed to specify which moment one co-ordinate refers. It has been therefore invented the age concept : all the coordinates specify respect to an age, and exist algorithms in order to pass from an age to the other.
In spite of the entity of the movement it can appear paltry on short periods, on a scale of time of millenia it can carry to remarkable variations in the positions of the stars; as an example, between approximately 13000 years the celestial North Pole it will be indicated from Vega, and not more from the Polar Star.
In spite of the entity of the movement it can appear paltry on short periods, on a scale of time of millenia it can carry to remarkable variations in the positions of the stars; as an example, between approximately 13000 years the celestial North Pole it will be indicated from Vega, and not more from the Polar Star.
Galactic Coordinates
The galactic coordinates take like plane of reference that galactic one that forms an angle of 62°41 ' with the celestial Equator and like direction of origin that one of the characterized from the measures of radio astronomy and placed galactic center in the constellation of the Sagittario (?=17h 42m 30s, and?=-28°55' 18").
These references allow to define a North Pole and a galactic South Pole through slowly galactic the normal direction al and passing for the Sun. The galactic North Pole has equatorial coordinates?=12h 49m and?=+27° 24'.
A galactic longitude (l) and a galactic latitude are defined (b), both measured in degrees.
The galactic latitude is traced on the great circles passing for the poles and varies from b=-90° (galactic South Pole) to b=+90° (galactic North Pole).
The varied galactic longitude from l=0° (center of the galaxy) to l=360° and is increasing in the back of spin of the Milky Way (seen from the North Pole the longitude grows in counter-clockwise sense).
These references allow to define a North Pole and a galactic South Pole through slowly galactic the normal direction al and passing for the Sun. The galactic North Pole has equatorial coordinates?=12h 49m and?=+27° 24'.
A galactic longitude (l) and a galactic latitude are defined (b), both measured in degrees.
The galactic latitude is traced on the great circles passing for the poles and varies from b=-90° (galactic South Pole) to b=+90° (galactic North Pole).
The varied galactic longitude from l=0° (center of the galaxy) to l=360° and is increasing in the back of spin of the Milky Way (seen from the North Pole the longitude grows in counter-clockwise sense).
equatorial Coordinates
They are reported to fixed references on the celestial sphere, therefore they do not vary with the position of the observer and the diurnal motion of s. the c.
They are taken like references:
* the celestial Equator;
* the hour circles;
* the ram point (), point of the celestial Equator in which the Sun is found when spring equinox passes from the celestial hemisphere south to thatnorth ().
The declination () of a star is its angular distance from the celestial Equator (from -90°, to the South Pole, +90° to the North Pole).
The right ascension () of a star is the angular distance between the intersection with the celestial Equator of its hour circle and the point of ram, measured towards east. The right ascension can also be expressed in second hours, minuteren and, placing 1 hour = 15°.
To times, in place of the declination the polar distance is used (p), that it is the angular distance of the star from the celestial North Pole and that varies from 0° to 180°. In any case, p +? = 90°.
They are taken like references:
* the celestial Equator;
* the hour circles;
* the ram point (), point of the celestial Equator in which the Sun is found when spring equinox passes from the celestial hemisphere south to thatnorth ().
The declination () of a star is its angular distance from the celestial Equator (from -90°, to the South Pole, +90° to the North Pole).
The right ascension () of a star is the angular distance between the intersection with the celestial Equator of its hour circle and the point of ram, measured towards east. The right ascension can also be expressed in second hours, minuteren and, placing 1 hour = 15°.
To times, in place of the declination the polar distance is used (p), that it is the angular distance of the star from the celestial North Pole and that varies from 0° to 180°. In any case, p +? = 90°.
Coordinated horizontal
Calls also "altazimutali coordinates", are reported to the observer, presupposed immovable, and therefore for every star they vary continuously, and they depend on the position of the observer. They are taken like references:
* the horizon, the maximum circumference that separates the visible celestial hemisphere from that invisibile;
* the meridian, the maximum circumference passing for the Zenith of the observer and the poles, that it meets the horizon in the points North and South;
* the foot of the star, point of the horizon more close to the star.
The height (h) is the angular distance of the star from the horizon, and varies between -90° (Nadir) and +90° (Zenith).
The Azimuth (a) is the angular distance between the point North and the foot of the star, measured in hour sense, and varies between 0° and 360°.
The smaller circumferences formed from the points of equal height are the height circles or almucantarat. The maximum semi-circumferences comprising the points of a data Azimut are called vertical.
To times, in place of the height the zenith distance is used them (z), that it is the angular distance of the star from the Zenith of the observer and that varies from 0° to 180°. In any case, z + h = 90°.
* the horizon, the maximum circumference that separates the visible celestial hemisphere from that invisibile;
* the meridian, the maximum circumference passing for the Zenith of the observer and the poles, that it meets the horizon in the points North and South;
* the foot of the star, point of the horizon more close to the star.
The height (h) is the angular distance of the star from the horizon, and varies between -90° (Nadir) and +90° (Zenith).
The Azimuth (a) is the angular distance between the point North and the foot of the star, measured in hour sense, and varies between 0° and 360°.
The smaller circumferences formed from the points of equal height are the height circles or almucantarat. The maximum semi-circumferences comprising the points of a data Azimut are called vertical.
To times, in place of the height the zenith distance is used them (z), that it is the angular distance of the star from the Zenith of the observer and that varies from 0° to 180°. In any case, z + h = 90°.
Celestial coordinates
The celestial coordinates serve in order to identify the position of the stars on the celestial sphere. Alternatively, inasmuch as in the truth they have various distances from we, the celestial coordinates characterize one oriented direction, that is one semistraight originated in the observer and passing for the star.
Meters on the sea level
The term meters on the sea level (m s.l.m.) one refers as an exampleto the altitude of a geographic point (locality or the top of a mount) or an object suspended in flight (like an airplane) regarding the medium sea level .
The altitude regarding the sea level is used in the transmissions of marks them radio or television in order to estimate the area of cover of it marks them. An other I use very important, beyond to the determination of the points in the geographic maps, is the control of the altitude of flight of the aircrafts.
It is important to notice that the definition of sea level is artificial in how much is not possible to determine of an only value for all the ondosi planet, since it varies with the tides, movements and other factors. In aviation the ellissoide of World-wide Geodetic Sistemais used in kind like reference (that the same one used from systems GPS is ).
The altitude regarding the sea level is used in the transmissions of marks them radio or television in order to estimate the area of cover of it marks them. An other I use very important, beyond to the determination of the points in the geographic maps, is the control of the altitude of flight of the aircrafts.
It is important to notice that the definition of sea level is artificial in how much is not possible to determine of an only value for all the ondosi planet, since it varies with the tides, movements and other factors. In aviation the ellissoide of World-wide Geodetic Sistemais used in kind like reference (that the same one used from systems GPS is ).
Standard Positioning System
The Standard Positioning System is a service supplied from the net of satellites of system GPS.
The SPS is used for uses civil, while service PPS remains classified to the military use. The SPS concurs to construct simple and economic receivers much and works on one single frequency (L1).
Until 2000, it marks them has been intentionally degraded through Selective Availability, reducing the positioning precision to approximately 100 meters of error. With the abandonment in the 2000 of the Selective Avalaibility system meters of error for the PPS offer pretazioni similar to those of PPS (8-60 meters of error for SPS against 6-20).
The SPS is used for uses civil, while service PPS remains classified to the military use. The SPS concurs to construct simple and economic receivers much and works on one single frequency (L1).
Until 2000, it marks them has been intentionally degraded through Selective Availability, reducing the positioning precision to approximately 100 meters of error. With the abandonment in the 2000 of the Selective Avalaibility system meters of error for the PPS offer pretazioni similar to those of PPS (8-60 meters of error for SPS against 6-20).
Precision Positioning System
The Precision Positioning System (PPS) is a service supplied from the net of satellites of the system Global Positioning System (GPS) specific for the military use.
The PPS is made up of two marks sendes them to you in the frequencies L1 (1575 MHz) and L2 (1227 MHz), while the Standard Positioning System (SPS) (marks used them in civil within) occupies only the L1.
As far as the pure performances of positioning PPS and SPS they are similar from when in 2000 it has been disabilitata the Selective Availability that degraded marks them civil. Often it is stretched to identify the precision erronamente as only advantage del PPS respect al marks them civil SPS. The characteristics that render the advanced PPS to the SPS comprise instead a greater resistance to disturb and the exclusive feature of I use from part of the single utilizzatori authorizes to you.
The PPS is made up of two marks sendes them to you in the frequencies L1 (1575 MHz) and L2 (1227 MHz), while the Standard Positioning System (SPS) (marks used them in civil within) occupies only the L1.
As far as the pure performances of positioning PPS and SPS they are similar from when in 2000 it has been disabilitata the Selective Availability that degraded marks them civil. Often it is stretched to identify the precision erronamente as only advantage del PPS respect al marks them civil SPS. The characteristics that render the advanced PPS to the SPS comprise instead a greater resistance to disturb and the exclusive feature of I use from part of the single utilizzatori authorizes to you.
Pseudolite
Pseudolite is an installed emitter GPS mostly, in stable way, to earth. This type of emitters concurs the land evolution of services GPS. It marks emitted them of Pseudolite simulate that emitted from the satellites, concurring mainly accurate localization and reliable thanks to the fact to be nearer the receivers regarding traditional emitters GPS it installs to you to edge of the satellites.
Pseudolite can increase cover GPS in hostile atmospheres as the canyon city or concurs the realization of services of localization in atmospheres indoor stands halo or integrated with the net to satellitare GPS.
Pseudolite can increase cover GPS in hostile atmospheres as the canyon city or concurs the realization of services of localization in atmospheres indoor stands halo or integrated with the net to satellitare GPS.
OpenStreetMap
OpenStreetMap is a collaborativo plan in order to create given maps to free content using from dispositi portable GPS and other free sources to you. The more common source for the data immessi in the OSM is portable units GPS. Many collaborators use programs like GPSBabel in order to convert data GPS from crude format (NMEA) or from an application of the XML forms owners to you to format GPX (). The data, like latitude/longitude, are collected in format WGS84 and are normally visualize to you on the projection of Mercatore.
Other tipologie of Assisted GPS
Since years ' 80 it has been attempted to obviate to the problem from the fixing trying to support the GPS with information that consentissero an express start of the receiver. To some models of receivers GPS, therefore, table with the ephemeres of satellites GPS has been given the possibility to acquire from external sources one. In origin such tables were loaded on the receiver through a connection with a computer; the complexity of such tables, however, limited the support to some days. In the more recent models, as an example in receivers GPS included in smartphone, the tables can be unloaded directly from Internet via GPRS or UMTS.
Assisted GPS
Assisted GPS, or A-GPS, is a system that concurs to pull down the necessary times to the first localization during the use of finishes them GPS. Extension its usefullness above all in "canyon" the city ones, which tight ways or remarkablly tree-lined tree-lined avenues, in which it is difficult to establish with precision the list of satellites in sight to finishes them. This system is showing a remarkable spread, and normally is associated to the systems of localization (LBS, Location System Base) bases to you on cellular telephony.
One of the main problems of finishes them to GPS classics is relative to the first localization ( the Fixing), in how much they finishes, to the ignition, must gain the list of the satellites in sight in that moment, for potervisi to couple and to try to find the own position. Such process is in somewhat expensive kind in terms of time and resources, and system A-GPS has been studied to the aim to pull down such costs, also in forecast of I use on finishes them with low abilities to elaboration or limited energetic resources, which the cellular telephones.
The main scope of this system is that one "to assist" receiver GPS in the calculation of the position, fornendogli information on the satellites in sight. Such methodology demands the support of the operator of mobile telephony.
The bottom idea is following: since every cell of present mobile telephony on the territory has a fixed position, it makes so that it is the cell to gain which are satellites GPS to it in sight, moment for moment. When A-GPS finishes them wants to know its position, it is connected through the cellular net to a Assistance Serveur (that it can also be managed from the same operator), to which comes sended also the information on the cell to which the customer it is coupled. Since the satellites in sight to the cell are famous, it can be assumed reasonably that also A-GPS finishes them sees the same satellites. Therefore the serveur elaborates a list with the satellites in sight, and it sendes it through the cellular net to finishes them, than in this way it can gain the own position immediately.
The reduced amount of data to send has suggested the employment of type messages cell broadcast, already wide uses you, as an example, in order to carry out various tariffazioni to second of the area in which the customer it finds, and that they appear on the screen of the customer under shape of indication of the province.
The protocol devised standard in order to comply with the own functionalities of A-GPS is the SUPL (Secure User Plane Location).
One of the main problems of finishes them to GPS classics is relative to the first localization ( the Fixing), in how much they finishes, to the ignition, must gain the list of the satellites in sight in that moment, for potervisi to couple and to try to find the own position. Such process is in somewhat expensive kind in terms of time and resources, and system A-GPS has been studied to the aim to pull down such costs, also in forecast of I use on finishes them with low abilities to elaboration or limited energetic resources, which the cellular telephones.
The main scope of this system is that one "to assist" receiver GPS in the calculation of the position, fornendogli information on the satellites in sight. Such methodology demands the support of the operator of mobile telephony.
The bottom idea is following: since every cell of present mobile telephony on the territory has a fixed position, it makes so that it is the cell to gain which are satellites GPS to it in sight, moment for moment. When A-GPS finishes them wants to know its position, it is connected through the cellular net to a Assistance Serveur (that it can also be managed from the same operator), to which comes sended also the information on the cell to which the customer it is coupled. Since the satellites in sight to the cell are famous, it can be assumed reasonably that also A-GPS finishes them sees the same satellites. Therefore the serveur elaborates a list with the satellites in sight, and it sendes it through the cellular net to finishes them, than in this way it can gain the own position immediately.
The reduced amount of data to send has suggested the employment of type messages cell broadcast, already wide uses you, as an example, in order to carry out various tariffazioni to second of the area in which the customer it finds, and that they appear on the screen of the customer under shape of indication of the province.
The protocol devised standard in order to comply with the own functionalities of A-GPS is the SUPL (Secure User Plane Location).
Conventional System Land WGS84
From the geometric point of view, the WGS84 is a particular conventional land system (CTS Conventional Terrain System), that is a system of cartesian reference used in order to describe the earth, whose characteristics are:
* center: in the center of mass of the earth
* Z axis: passing for the North Pole, like defined from the BIH in 1984
* axis X: passing for the meridian of Greewich, like defined from the BIH in 1984
* Y axis: chosen so as to to give a tern right-handed, that is such that an observer long place the Z axis sees axis X sovrapporsi to Y with counter-clockwise motion, that he places Y in Asia.
* center: in the center of mass of the earth
* Z axis: passing for the North Pole, like defined from the BIH in 1984
* axis X: passing for the meridian of Greewich, like defined from the BIH in 1984
* Y axis: chosen so as to to give a tern right-handed, that is such that an observer long place the Z axis sees axis X sovrapporsi to Y with counter-clockwise motion, that he places Y in Asia.
WGS84
WGS84 is the acronym of World Geodetic System 1984 and defines the system like geodetic, world-wide, reported to 1984.
It constitutes a mathematical model of the Earth from a geometric, geodetic andgravitational point of view , constructed on the base of the measures and the scientific and technological acquaintances available to 1984.
The datum of classic geodesy, that they can be defined local or regional, approximates the single geoide well in around of the emanation point, while total datum WGS84 uses standard EGM96, that it approximates the geoide in its complex and is valid all over the world.
From 2000 it is obligatory I use it of the WGS84 like standard for the air navigation. In Italy however it is still in course (the 2005) conversion of the aeronautical data ofthe ENAV from old standards ED50 and MM40 to the WGS84, whilethe Italian Air Force has finished the conversion in 2002.
It constitutes a mathematical model of the Earth from a geometric, geodetic andgravitational point of view , constructed on the base of the measures and the scientific and technological acquaintances available to 1984.
The datum of classic geodesy, that they can be defined local or regional, approximates the single geoide well in around of the emanation point, while total datum WGS84 uses standard EGM96, that it approximates the geoide in its complex and is valid all over the world.
From 2000 it is obligatory I use it of the WGS84 like standard for the air navigation. In Italy however it is still in course (the 2005) conversion of the aeronautical data ofthe ENAV from old standards ED50 and MM40 to the WGS84, whilethe Italian Air Force has finished the conversion in 2002.
EGM96
EGM96 (Earth Geopotential Model 1996) is a geopotenziale model of the land surface constituted from one sum of spherical harmonicas until 360° the order and degree. It is a solution composed of with of equations differentiates them, formed give:
1. one arranged solution of 70° the order and degree
2. a diagonal solution to blocks from the degree 71° until the 359°
3. the solution of quadrature for the degree 360°
This model is the result of one collaboration between the National Imagery and Mapping Agency (NIMA), the Goddard Space Flight Center of NASA andthe Ohio Been University.
In the preparation of the map with resolution 30' x30 ' of the gravity anomalies , beyond to the values it uses you in the previous models, has been assembled one new topographical base of data of all the sources available. The base of data then is used for the isostatico filling of the globe part not covered from the data (approximately 3% of the total). Model EGM96 has been used like geodetic reference in order to modernize the WGS84.
1. one arranged solution of 70° the order and degree
2. a diagonal solution to blocks from the degree 71° until the 359°
3. the solution of quadrature for the degree 360°
This model is the result of one collaboration between the National Imagery and Mapping Agency (NIMA), the Goddard Space Flight Center of NASA andthe Ohio Been University.
In the preparation of the map with resolution 30' x30 ' of the gravity anomalies , beyond to the values it uses you in the previous models, has been assembled one new topographical base of data of all the sources available. The base of data then is used for the isostatico filling of the globe part not covered from the data (approximately 3% of the total). Model EGM96 has been used like geodetic reference in order to modernize the WGS84.
GLONASS
GLObal NAvigation System Satellite) is the positioning system to satellitare Russian, controparte of the Global Positioning System of the United States and the system of European Galileo positioning. It is managed from the Russian army.
In the period of maximum efficiency the system offered to services of positioning and time standard with an accuracy in horizontal of 55 meters, vertical 70 meters, measure of speed in 15 cm/s and time 1 µs when the receiver was in sight of four satellites. It marks taken care of them more was to disposition of the single Russian soldiers.
Like the GPS, official fleet GLONASS comprises 24 satellites, 21 acts to you and three of supply, decided on three orbital plans. Every slowly it accommodates eight satellites identifies to you from a number of slot that it identifies the satellite and the plan: 1-8, 9-16, 17-24. The three plans are separate to you from 120° and the satellites of a same one slowly distance to you 45° between they. The orbits are almost circulars with an inclination of 64,8° and a greater axle shaft of 25440 km. the satellites orbit to a 19100 quota Km, leggermente inferior to satellites GPS and complete one every spin 11 hours and a quarter. In this way at least five satellites are visible in every moment.
All the satellites have been launch from the cosmodromo of Baikonur in Kazakhstan, first in October 1982, rendered operated to you in December 1983. The system would have had to be operating already in 1991, but after a first dismissal to 1993 the activation was not completed before December 1995.
Because of the serious economic situation of Russia, in the 2002 still was operated only eight satellites to you, and the net was almost unusable. With improving of the economic situation the satellites operated were capacities to 11 in March 2004. Three satellites of new conception, with an extended operating life to seven years, were launch 26 December 2004. Later on to an agreement they with Indiatrades, the net would have to return totally operating in 2007.
However the system also is penalized from the cost of receivers GLONASS and from their difficult reperibilità.
In the period of maximum efficiency the system offered to services of positioning and time standard with an accuracy in horizontal of 55 meters, vertical 70 meters, measure of speed in 15 cm/s and time 1 µs when the receiver was in sight of four satellites. It marks taken care of them more was to disposition of the single Russian soldiers.
Like the GPS, official fleet GLONASS comprises 24 satellites, 21 acts to you and three of supply, decided on three orbital plans. Every slowly it accommodates eight satellites identifies to you from a number of slot that it identifies the satellite and the plan: 1-8, 9-16, 17-24. The three plans are separate to you from 120° and the satellites of a same one slowly distance to you 45° between they. The orbits are almost circulars with an inclination of 64,8° and a greater axle shaft of 25440 km. the satellites orbit to a 19100 quota Km, leggermente inferior to satellites GPS and complete one every spin 11 hours and a quarter. In this way at least five satellites are visible in every moment.
All the satellites have been launch from the cosmodromo of Baikonur in Kazakhstan, first in October 1982, rendered operated to you in December 1983. The system would have had to be operating already in 1991, but after a first dismissal to 1993 the activation was not completed before December 1995.
Because of the serious economic situation of Russia, in the 2002 still was operated only eight satellites to you, and the net was almost unusable. With improving of the economic situation the satellites operated were capacities to 11 in March 2004. Three satellites of new conception, with an extended operating life to seven years, were launch 26 December 2004. Later on to an agreement they with Indiatrades, the net would have to return totally operating in 2007.
However the system also is penalized from the cost of receivers GLONASS and from their difficult reperibilità.
Galileo Services
They are the four services that Galileo will offer:
* The Open Service (OS) will be accessible to anyone. The receivers will horizontally concur an inferior accuracy with the 4 meters and 8 meters vertically.
* The Commercial Service (CS) criptato will concur behind payment of having an inferior accuracy to the meter. The CS could be completed from stations to earth in order to carry the inferior accuracy to i 10 cm.
* The Public Regulated Service (PRS) and the Safety of Life Service (SoL) cripta will offer a comparabile accuracy to you with the service Open Service. Their main scope is the robustness against disturbs and the reliable survey of the problems within 10 second ones. They are specifically plans to you, respective, for operating of emergency (police, military, etc) and applications for the emergency in the transports (air-traffic control, automated landing of aircrafts, etc).
* The Open Service (OS) will be accessible to anyone. The receivers will horizontally concur an inferior accuracy with the 4 meters and 8 meters vertically.
* The Commercial Service (CS) criptato will concur behind payment of having an inferior accuracy to the meter. The CS could be completed from stations to earth in order to carry the inferior accuracy to i 10 cm.
* The Public Regulated Service (PRS) and the Safety of Life Service (SoL) cripta will offer a comparabile accuracy to you with the service Open Service. Their main scope is the robustness against disturbs and the reliable survey of the problems within 10 second ones. They are specifically plans to you, respective, for operating of emergency (police, military, etc) and applications for the emergency in the transports (air-traffic control, automated landing of aircrafts, etc).
The innovationes of Galileo
The differences with the GPS are multiple, these regard are the structure of the same satellites that over all the services offers. The applications and the services as soon as it lists to you demand of the particular characteristics and unfortunately many of these lack to put into effect them system GPS.
An example of the innovation introduced from GALILEO regards the reliability in the guarantee of the service, the authentication of marks them, integrity, the transparency of the operations, the possibility of dealing given raw or proceeded to you, the accuracy and the reliability of the system.
Beyond to all these characteristics, Galileo Supervisory Authority and Galileo Concessionaire they will give place to a framework institutional with the task of regulating and facilitating the exploitation of Galileo to level of the total market. The applications that are born every day are very many in fact, this enormous market, are destined to catch up 3 billions of customers within 2020.
An example of the innovation introduced from GALILEO regards the reliability in the guarantee of the service, the authentication of marks them, integrity, the transparency of the operations, the possibility of dealing given raw or proceeded to you, the accuracy and the reliability of the system.
Beyond to all these characteristics, Galileo Supervisory Authority and Galileo Concessionaire they will give place to a framework institutional with the task of regulating and facilitating the exploitation of Galileo to level of the total market. The applications that are born every day are very many in fact, this enormous market, are destined to catch up 3 billions of customers within 2020.
Ground Control System
The structure of the GALILEO Ground Control System is composed from a Navigation System Control Center (NSCC), one total net of Stations of Orbitography and Synchronization (OSS), one series of stations of tracking remote, telemetry and commando (TT&C) as illustrated in figure. Every OSS carries out of the measurements that come together sended to the NSCC to the navigation messages coming from from the GALILEO satellites, to meteorological information and other data.
On the credit side inside dell'NSCC, the Satellite Control Facilities (SCF) carries out the maintenance goddesses satellites, controls the orbits, carries out telemetry and control to distance through stations TT&C. The NSCC comprises also the Orbitography and Synchronisation Processing Facility (OSPF), the Precision Timing Station (PTS) and the Navigation Control Facility (NCF).
The OSPF calculates the ephemeres for every satellite, the offset one of the clocks to edge and carries out one predizione of these parameters in order to generate the SISA (signal in-space accuracy).
The PTS instead comprise the atomic clocks to high precision that generate the GALILEO System Time (GST), that is the reference of time of the system.
The NCF finally, is taken care to control, to monitorare and to manage the OSPF, OSS, PTS and NCF. An external interface to the system exists moreover that is taken care to manage the communication with external entities, the Service Centres Interface.
On the credit side inside dell'NSCC, the Satellite Control Facilities (SCF) carries out the maintenance goddesses satellites, controls the orbits, carries out telemetry and control to distance through stations TT&C. The NSCC comprises also the Orbitography and Synchronisation Processing Facility (OSPF), the Precision Timing Station (PTS) and the Navigation Control Facility (NCF).
The OSPF calculates the ephemeres for every satellite, the offset one of the clocks to edge and carries out one predizione of these parameters in order to generate the SISA (signal in-space accuracy).
The PTS instead comprise the atomic clocks to high precision that generate the GALILEO System Time (GST), that is the reference of time of the system.
The NCF finally, is taken care to control, to monitorare and to manage the OSPF, OSS, PTS and NCF. An external interface to the system exists moreover that is taken care to manage the communication with external entities, the Service Centres Interface.
The final satellite
To the end of phase IOV (In-Orbit Validation), like already pointed out, there will be the completion of the entire constellation of satellites.
Its geometry is designed in order to allow the multiple launch using launchers of Arianes type or similari. The position of the satellite in the orbit has been studied in such way to concur perennially with the solar paddles of being exposed to the direct beams of the sun (sees figure).
The payload he is much similar one to that one described for satellites GIOVE.
Its geometry is designed in order to allow the multiple launch using launchers of Arianes type or similari. The position of the satellite in the orbit has been studied in such way to concur perennially with the solar paddles of being exposed to the direct beams of the sun (sees figure).
The payload he is much similar one to that one described for satellites GIOVE.
Giove-B Satellite
Stabilized on three aces 2,4 m have a body of dimensions 0,95 x 0,95 x. One mass to the launch of 530 kg. The length of wing of the solar paddles is of 4.34 m, which supply 1100 W of power. The propulsion happens through a motor to idrazina fed from one bottle of 28 kg.
The payload he is doubly redundant and it comprises: phased an Array of antennas in L band, a generator of marks them, a clock hydrogen-maser and two to the rubidio, a monitor for the control and the measure of cancellations.
The payload he is doubly redundant and it comprises: phased an Array of antennas in L band, a generator of marks them, a clock hydrogen-maser and two to the rubidio, a monitor for the control and the measure of cancellations.
Giove-A Satellite
The satellite is stabilized on three aces. Massa to the launch of 600 kg has a body of cubical shape of dimension 1,3 x 1,8 x 1,65 m., demanded of power of 700 W satisfied through two wings with long solar paddles 4,54 m. The propulsion is to butane with two bottles from 25 kg. The payload he is three times redundant and it introduces: an antenna phased Array in L band, the generation unit marks them, two atomic clocks to rubidio with one the precision of 10 nanoseconds, of the monitor for measures cancellations, the navigation receiver.
Giove
In 2002 in preparation of the completion of GALILEO,the ESA has experienced the development of the system with the introduction of two satellites GIOVE-A and GIOVE-B (beyond to the earth segment). This has carried to a great progress in the technology spaces them European, obtaining it never objects to you caught up which before I use it of an orbit MEO for navigation satellites, the putting to point of clocks never therefore you specify and the experimentation of new systems of transmission and treatment of marks them and of navigation.
System of Galileo positioning
The system of Galileo positioning (in English Galileo positioning system) is a navigation system to satellitare civil developed in Europe like alternative to the Global Positioning System (GPS), controlled from the Department of the Defense of the United States.
Its commissioning is previewed for 2013 and will count on 30 orbiting satellites on 3 plans tilts on the Equatorto one quota to you 24.000 km.
The main scopes of Galileo are:
* A greater precision to all the customers regarding that one puts into effect them;
* An improved cover of marks them from the satellites, above all for the regions higher latitudes;
* A system of total positioning that can always work also in times of war.
Its commissioning is previewed for 2013 and will count on 30 orbiting satellites on 3 plans tilts on the Equatorto one quota to you 24.000 km.
The main scopes of Galileo are:
* A greater precision to all the customers regarding that one puts into effect them;
* An improved cover of marks them from the satellites, above all for the regions higher latitudes;
* A system of total positioning that can always work also in times of war.
Geographic coordinates
The geographic coordinates serve to identify the position of a point on the land surface.
The longitude ( distance angular is the latitude (angulardistance from the Equator) along the parallel of the place from an arbitrary prime meridian ). The latitudes and the longitudes are expressed in seconddegrees, minuteren and. Currently the meridian of Greewich is used who passes for omonimo the observatory.
Geographic coordinates are formed therefore: xx° xx' xx"N yy° yy' yy" and
An example: 41° 53' 24"N 12° 29' 32" and are the coordinates of the second Colosseo Google Earth
In Italy it was use (not of all scomparso) using like prime meridian that one passing forthe observatory of Mario Mount (to Rome, 12° 27,2 ' and of Greewich). Such system of coordinates came usedMilitary Geographic Institute (IGM) in order to modernize to the data to the standard World Geodetic System84 (WGS84), on which Sistema of total positioning (GPS is based also). Standard WGS84 is based on a geodetic model of the Earth standard.The EGM96 is a geoide defined from a system of spherical harmonicas.
The longitude ( distance angular is the latitude (angulardistance from the Equator) along the parallel of the place from an arbitrary prime meridian ). The latitudes and the longitudes are expressed in seconddegrees, minuteren and. Currently the meridian of Greewich is used who passes for omonimo the observatory.
Geographic coordinates are formed therefore: xx° xx' xx"N yy° yy' yy" and
An example: 41° 53' 24"N 12° 29' 32" and are the coordinates of the second Colosseo Google Earth
In Italy it was use (not of all scomparso) using like prime meridian that one passing forthe observatory of Mario Mount (to Rome, 12° 27,2 ' and of Greewich). Such system of coordinates came usedMilitary Geographic Institute (IGM) in order to modernize to the data to the standard World Geodetic System84 (WGS84), on which Sistema of total positioning (GPS is based also). Standard WGS84 is based on a geodetic model of the Earth standard.The EGM96 is a geoide defined from a system of spherical harmonicas.
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