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I am having trouble configuring a GPS module. According to the data sheet it has 20HZ update rate and 2.5m accuracy. However, the results usually shift between 10m to 100m away from what they are supposed to be. There are so many terms involving GPS that I am not familiar with so I only configured baudrate, power mode and output message interval.

Setup:

uC UART to GPS module. Both of them are at 3.3v
baudrate: 115200 (highest)
update rate: 20HZ (highest)
output message: $GPGGA
output rate: Every 3s
datum: WGS-84
I use Google map to check position(which also uses WGS-84)

My project only involves moving at around 1m/s on the street with a clear view of sky( there are buildings around). The GPS doesn't have a backup battery for its RTC so it does cold start every time. The led on it indicates the position has been fixed when I log the results.

Is there anything I can configure to get more precise GPS coordinates?

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Is there anything I can configure to get more precise GPS coordinates?

Maybe ensure WAAS is on.

0x37 55 Input Configure WAAS Configure the enable or disable of WAAS 
0x38 56 Input Query WAAS status Query WAAS status of GPS receiver 

GPS receivers can take a long time to get an accurate fix from cold start (many minutes).

To some extent, accuracy depends on number of satellites in view (and signal strength) Tall buildings nearby can reduce the number of satellites visible to the receiver.

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  • \$\begingroup\$ Thanks. I turned WAAS on and there is indeed some improvements. I found an article on testing different GPS modules. The Pedestrian test gives me an idea that GPS works better if you are moving faster. gpspassion.com/forumsen/topic.asp?TOPIC_ID=89352 \$\endgroup\$ – Timtianyang Dec 3 '13 at 21:26

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