GPS Ultimate Breakout Board Position Wrong

[Alumen]

So I recently purchased a GPS ultimate Breakout Board with USB to TTYL adapter for my raspberry pi. After getting a fix and grabbing data from the GPS and plotting it, it seems that the position that the GPS is giving me is consistently off by about 0.2 miles north. It is tracking my distance I moved and direction perfectly fine however it is giving me a position 0.2 miles north of where I actually am. I have plotted my position using Google maps, google earth, and Apple maps and they all do they same thing. It is VERY important for my project that I have accurate positional information as I will lose my rover and pi if I do not have a correct location.
Does anyone know what to do about this issue??

[Franklin97355]

Have you looked at the raw data being sent from the GPS (echo.pde) ? What code are you using to get the data?

[adafruit_support_mike]

You're probably treating the GPS output as a decimal value.

It isn't.

The GPS module reports position in degrees, minutes, and decimal fractions of a minute. The two digits to the left of the decimal point only go up to 59.

The format for latitude is DDMM.MMMM
The format for longitude is DDDMM.MMMM

There's a note about it on this page of the GPS tutorial:
https://learn.adafruit.com/adafruit-ult ... ter-wiring

[Alumen]

I a missing the GPGGA string, and no I wrote a parser to convert it to degrees minutes and seconds.
I have treated the device as a serial device and wrote code using the python library pyserial to grab data and parse the GPGGA lines. It is just weird that it can track my position and movement perfectly but it is always 0.2 miles off.

[Alumen]

Welp, I solved the issue. It was indeed an error in the way I was parsing the data. It works fine now. Thanks for the help!