Car navigation systems buy knowledge

1¡¢Navigator gps receiver

A total of 24 gps satellites orbiting along six tracks, each of these four as a group, in general, not more than 12 satellite side of the Earth at the same time. Most gps navigator receiver can track the satellite in about 8 to 12. Calculation of the LAT / LONG, (2 dimensional) coordinates of at least three satellites. Plus one can calculate the three-dimensional coordinates. For a given position, the navigator will be able to know at this point what satellites in the vicinity, because it is constantly receiving updates sent from the satellite signal.

2¡¢Signal of the parallel channel

The number of car navigation systems have two to five parallel channels to receive the satellite signals. Because there may be up to 12 satellites are visible (average 8) This means that the gps receiver in the navigator must follow a certain order to access each satellite, to obtain information about each satellite.

Most of the market gps receiver 12 parallel channel type, which allows them to continuously track each satellite's information, 12-channel receiver advantages include rapid cold start and initial satellite information, and in forest areas have a better reception. General, 12-channel receiver is a need for an external antenna, unless you are in an enclosed space, such as in the cabin compartment.

3¡¢Satellite positioning time

This is when you restart your navigator, gps receiver also followed restart the receiver to determine the current location of the time required. For 12-channel receiver, if you are near the location of the last positioning when the cold start positioning time is generally three to five minutes, hot start for 15 to 30 seconds, mostly for two-channel receiver, the cold start, more than 15 minutes, hot start for 5 minutes.

4¡¢gps positioning accuracy

Most of the horizontal position of the GPS receiver positioning accuracy of about 5m ~ 10m, but only in SA is not open.

5¡¢DGPS function

To SA and the atmosphere reflects the impact of reduced to a minimum, there is something called the DGPS transmitter equipment. It is a fixed GPS receiver (set in an exploration site within a radius of 100km ~ 200km) to receive the satellite signal, it knows exactly theoretically the satellite signal to the exact time is it the actual transmission time , and then calculate the "difference", which is very close to the SA and atmospheric refraction effects of this difference it will send out other GPS receiver can use it to get a more accurate location reading (5m ~ 10m or less error).

Provider of GPS devices in some areas to set up DGPS transmitter for its customers to use free of charge, as long as the customer to buy a GPS receiver DGPS function.

6¡¢Signal interference

To give you a good positioning of the GPS receiver needs at least five satellites are visible. If you are in the canyon, or on both sides of the skyscrapers, streets, or in the dense jungle, you may not be able to contact with enough satellites, which can not locate or can only get the two-dimensional coordinates. Similarly, if you are inside a building, you may not be able to update your location, some GPS receivers have a single antenna can be attached to the windshield, or an external antenna can be placed on the roof, which helps you receiver to get more satellite signals.

7¡¢Physical indicators of the navigator

When you buy a GPS device, the size, weight, screen, waterproof, shockproof, dustproof performance, high temperature, power consumption and other physical indicators should be taken into account.