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
5,776
Read your datasheet and find the exact data format used, 13.121540° is 13°7'17.544" which is exactly the error youre seeing.