In addition to referencing the authoritative navigation device hot list or the latest car navigation brand rankings, some GPS basic knowledge is also necessary. Below, the car China will organize the common sense of GPS, so that you can not be fooled by the merchant when purchasing the navigator! This article refers to the address: http:// 1, navigator GPS receiver We have a total of 24 gps satellites orbiting the Earth along six orbits, each of which is a group. In general, there will be no more than 12 satellites on one side of the Earth at the same time. So, what do we have for our navigation? Help? The receivers in most gps navigators can track around 8 to 12 satellites. At least 3 satellites are required to calculate the LAT/LONG (2D) coordinates. Add one more to calculate the 3D coordinates. For a given location, the navigator knows which satellites are nearby at this time because it constantly receives updates from the satellite. Some merchants like to brag about how superior the performance of their products is, how many satellites can be found in one breath, then we have to think about how much water is in his product! 2. Parallel channel of signal Some car navigation systems can have 2 to 5 parallel channels to receive satellite signals. Since up to 12 satellites are visible (average is 8), this means that the gps receiver in the navigator must access each satellite in a certain order to obtain information for each satellite. Most of the GPS receivers on the market are 12-parallel channel type, which allows them to continuously track the information of each satellite. The advantages of the 12-channel receiver include fast cold start and initialization of satellite information, and there can be more in the forest area. Good reception. Generally, a 12-channel receiver does not require an external antenna unless you are in a closed space, such as a cabin or a car. 3. Satellite positioning time This means that when you restart your navigator, the gps receiver is also restarted, knowing the time it takes for the receiver to determine the current location. For a 12-channel receiver, if you are near the last positioning position, the positioning time for cold start is generally 3 to 5 minutes, and for hot start is 15 to 30 seconds, while for 2-channel receivers, cold start is mostly exceeded. 15 minutes, 2 to 5 minutes on hot start. 4, GPS positioning accuracy The positioning accuracy of the horizontal position of most GPS receivers is about 5m ~ 10m, but this is only when the SA is not turned on. 5, DGPS function In order to minimize the effects of SA and atmospheric refraction, there is a device called a DGPS transmitter. It is a fixed GPS receiver (set in a radius of 100km to 200km on an exploration site) to receive satellite signals. It knows exactly what the precise time the satellite signal is theoretically transmitted, and then compares it with the actual transmission time. Compare and then calculate the "difference", which is very close to the effect of SA and atmospheric refraction, which sends this difference and other GPS receivers can use it to get a more accurate position reading (5m ~ 10m or less) Error). Many GPS equipment providers have set up DGPS transmitters in some areas for their customers to use for free, as long as the GPS receivers purchased by customers have DGPS capabilities. 6, signal interference To give you a good positioning, the GPS receiver needs at least 3 to 5 satellites to be visible. If you are in a canyon or on a street lined up in two high-rise buildings, or in a dense jungle, you may not be able to contact enough satellites to locate or only get two-dimensional coordinates. Similarly, if you are in a building, you may not be able to update your location, some GPS receivers have separate antennas that can be attached to the windshield, or an external antenna can be placed on the roof, which will help you The receiver gets more satellite signals. 7, physical indicators When purchasing GPS equipment, physical indicators such as size, weight, display screen, waterproof, shockproof, dustproof performance, high temperature resistance, and power consumption must be taken into account.
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