What is the meaning of 20 channels of GPS module?

The GPS module has a parameter of channel number, เช่น 20 channels. It means that the module can establish communication with 20 satellites at the same time. Three satellites are required for 2D positioning, and the data is unstable. The module can obtain the correct positioning data only after receiving more than three satellite signals simultaneously. If the number of satellites communicating at the same time is higher, the module will be faster and more accurate. In the general urban environment on the earth’s surface, the positioning data can be communicated with 4-11 satellites at the same time.

Why does the GPS module take a long time to get positioning data after starting up?

If the GPS module has been powered on for the first time, or if it has been powered off for more than four hours, it may take longer to achieve positioning. This is because the GPS module needs to perform a cold start. S-87 has a built-in button battery that can store ephemeris data in the module, allowing for quicker positioning (hot start) when powered on again within four hours.

Troubleshooting Cold Start Positioning Issues

What to do if cold start positioning is not possible for a long time?

If cold start positioning takes too long, it is necessary to check whether the GPS antenna is placed in an open environment and whether the GPS data output by the GPS module can be read. The module can output positioning data such as $GPGGA,$GPGSA, $GPGSวี,and$GPRMC once per second. We usually use $GPRMC to obtain important information like longitude, latitude, speed, direction of motion, and timestamp. If issues persist, check if the GPS satellite signal state can be observed in the GSV statement of GPS data.

Antenna Condition Monitoring

What about antenna condition monitoring?

What should be done when the antenna is short-circuited? The best approach is for the GPS module to output a statement indicating the antenna’s open and short-circuit status, prompting customers to check this aspect. This method allows customers to easily identify problem points and protects the module from high current impact. Many modules on the market, such as S-87, S-90, S-93, and Ublox, have this function. อย่างไรก็ตาม, Ublox may require peripheral devices to realize this function, while others do not. นอกจากนี้, this function may only be available in the flash version and not configurable via the IO port in the ROM version.