Car GPS / GPRS terminal speed principle
GPS to determine and calculate the speed of the principle is that the GPS receiver (operating frequency 1575.34M) can be used to output TTL number as noted in the specific latitude and longitude coordinates of each second, and then divided by one second, is the average speed in one second. In practice, due to various errors, resulting in such calculated data can not be so accurate. In fact, GPS receivers use the Doppler Effect to calculate forward speed, which can be as accurate as 0.5 kilometers per hour.
The Doppler effect
The Doppler effect doesn't just apply to sound waves; it applies to all types of waveforms, including electromagnetic waves. Scientist Edwin Hubble discovered that the frequency of light from distant galaxies is becoming higher, i.e., shifting to the red end of the spectrum. This is the red Doppler shift, or redshift. If the Milky Way is moving toward him, the light becomes blueshifted, thus using the Doppler effect to conclude that the universe is expanding.GPS satellites also emit electromagnetic waves, and in the same way, the receiver's own speed can be derived from a comparison of the frequency of the electromagnetic waves received and the theoretical frequency of the satellite's emissions. In order to measure the exact speed of a few centimeters per second, a wavelength of several centimeters is needed, so GPS satellites use microwaves, which have a wavelength of a few centimeters or so.
Because of the known orbit of GPS satellites, satellites will broadcast ephemeris information (Almanac) contains Kepler orbit information, the information can predict the position of GPS satellites at each moment, your GPS receiver reads these ephemeris information and write it into its non-volatile memory (Non-Volatile Memory) in the receiver will not forget, even after the receiver is turned off. Even after the receiver is turned off, it will not forget the ephemeris. So we know that GPS satellites don't just send out pseudo-gibberish for ranging, they also broadcast other information such as orbital position, and we'll talk more about pseudo-gibberish later.
Fixed orbits must be directly above the equator, so users near the poles can hardly see satellites in fixed orbits. Secondly, if all the satellites are in the same plane, the positioning is called a very high degree of accuracy fade, and it is difficult to calculate the correct location, so GPS satellites are evenly distributed in every corner of the globe in the air, the cycle of about 12 hours. Furthermore, we know that the satellite fleet is constantly monitored by ground stations operated by the U.S. Department of Defense to communicate with each other. Ground-based facilities need to be able to see them twice a day in order to check their positions, clocks and health, and to upload information for broadcast to us. The ground monitoring facilities also need to accurately predict the position and speed of the satellites, since orbits are subject to slight variations due to the solar wind, the moon or the sun's gravity, and since maneuvering the satellites is a burden on the limited fuel resources and control, it is not usual to maneuver the satellites back to the correct predicted Keplerian orbits, and so the satellites are only maneuvered when the monitoring section has difficulty in predicting the orbital parameters of the satellites. Small variations in orbit and clock are corrected by a set of satellite orbit parameters called precise orbit data, which GPS satellites are corrected for by ground-based monitoring facilities, so the satellites also broadcast precise orbit data for your receivers to process. If the monitoring component detects that the GPS satellite has deviated from the predicted orbit, it uploads new precise orbit data to the satellite, which broadcasts the corrections so that the GPS receiver can make accurate position calculations. So, for these reasons, GPS uses a near-Earth orbit rather than a synchronous one.
In summary, the GPS receiver receives more than or equal to 3 satellites in the sky signal, will quickly and proficiently measured his speed value (183) and expressed in digital terms, with a wireless network sent to the monitoring center in real time displayed on electronic maps.
GPS cell phone to achieve navigation, in addition to hardware, but also need the support of software maps, commonly known as GPS navigation software. Then as the name suggests, cell phone GPS navigation software is also can be installed in the cell phone operating platform (system) on the navigation software. Tiger Maps is a free GPS cell phone map software, also supports the navigation function, of course, at present Tiger Maps navigation function does not have the voice navigation function - we have received a lot of users voice navigation function of the proposal and the corresponding other good suggestions, here thanks to the vast number of users on the Tiger Maps support, Tiger Maps Tiger Maps will fully consider the opinions of our users.
While Tiger Maps doesn't support voice navigation, it can be used as a simple GPS phone navigation software to provide on-screen navigation, which basically meets the GPS navigation needs of most users. For example, we have received feedback from users that they found reasonable routes to their homes in cabs using Tiger Maps' "Self-Drive" navigation feature. navigation function to find a reasonable route home example.
GPS navigation software, the basis of the principle is positioning. GPS is the English Global Positioning System (Global Positioning System) abbreviation. GPS, simply put, this is a satellite system consisting of 24 satellites covering the whole world, can provide real-time, all-weather and global navigation services. GPS global positioning system consists of three parts: the space part of the GPS satellites; ground control part of the ground monitoring system; user equipment part of the GPS signal receiver (i.e., the ground monitoring system). -GPS signal receiver (i.e. personal user terminal). To put it simply, it is the user who receives the satellite signal through GPS, and obtains the user's position, speed and other information through signal processing, and finally realizes the purpose of using GPS for positioning.
Can be understood as a positioning in the map of a point, and an object to move, accompanied by changes in positioning, if not listen to the positioning, then we will get a string of electricity, these points are connected in order to form a line, in the map is a mobile route. In turn, we find an optimal route to carry out on the map, and then in the process of our driving constantly positioning, while comparing with the route on the map, to ensure that the positioning point and the line overlap, it will realize the navigation function.
Tiger Maps GPS navigation function is realized in the same principle, of course, the navigation is only one of the functions of Tiger Maps, Tiger Maps in addition to the navigation function, can be used as an essential cell phone mapping tool in life. Tiger Maps supports three kinds of positioning methods, GPS, base station and Wifi; bus transfer query; map query; neighborhood query; maps of more than 400 cities in the country in the hands of dining, accommodation, entertainment, shopping, transportation, finance and other life information; map sharing; ultra-smooth map browsing, using the industry's top vector compression technology, no vignetting random zoom in, zoom out, and panning, industry's The smallest map data package; support for offline maps; software and map data update function.