# extracting data from GPS pls help

#### pawankumar

Joined Oct 28, 2009
42
Hi friends,

I tried interfacing GPS module with PC to extract the co ordinates (lat,long)

As soon as I connected the device to serial port @9600 baud, it started spitting data.

as per NMEA(pretty straight forward), I extracted latitude and longitude from the $GPGGA string. but every time I land up to a place about 30Km away from home . Then I used the software GPSCockpit, which provided the exact co-ordinates of my house. This is mystery to me. for instance, a GGA string i received is like:$GPGGA,075529.844,1307.2917,N,08012.5775,E,1,4,1.34,30.2,M,-88.5,M,,*40

this gives the (lat, long) data 13.072917N,080.125775E

but the original co ordinates are (13.121540,80.209590)

How do I get this? I ve done a lot of google search to ensure no one else has faced a similar problem. Please suggest me proceed further.

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#### pawankumar

Joined Oct 28, 2009
42

#### davebee

Joined Oct 22, 2008
540
The numbers that look bad are timestamped 7:55:29, but the good numbers are timestamped 7:55:50.

If you compare readings of about the same timestamp, do they still show about the same 30 km offset?

#### pawankumar

Joined Oct 28, 2009
42
@davebee :

Thanks 4 your response. I am experimenting this with my desktop. so, no chance to move .

I feed the raw data into this site, it gives me the exact location

http://youngindia99.com/gps.aspx

There are many such apps.but I just need the method how these guys do it

#### pawankumar

Joined Oct 28, 2009
42
Got it!!!!

this one seems to work

to convert NMEA co ordinates into google understandable co ordinates,

1307.2917===>13+07.2917/60 =13.12152

this is a blind guess work

anyone knows the logic please let me know

#### davebee

Joined Oct 22, 2008
540
Google must give the location in fractions of a degree instead of in degrees, minutes and seconds.

0.12152 degrees * 60 minutes/degree = 7.2912 minutes

#### kubeek

Joined Sep 20, 2005
5,718
Read your datasheet and find the exact data format used, 13.121540° is 13°7'17.544" which is exactly the error youre seeing.