for reading gpx file (may be in text file) use this code in matlab,

P = gpxread(filename);

then reading these documentations

http://www.mathworks.com/help/curvefit/least-squares-fitting.html

http://www.mathworks.com/help/optim/ug/least-squares-model-fitting-algorithms.html

you can perform Least square adjusment programme on your gpx file in matlab,

these are the also file exchanges (build in tools in matlab) for proccessing gps dataset

https://www.mathworks.com/matlabcentral/fileexchange/38934-processing-gpx-file

https://www.mathworks.com/matlabcentral/fileexchange/24154-gpx-file-reader

In matlab there is the GPS software toolbox

Another is the RTKLIB , this is free

Hi, 

you could try out also goGPS: http://www.gogps-project.org/

We have been developing it since 2007, and it includes several positioning strategies, including epoch-by-epoch least squares adjustment and Kalman filtered solutions.

There is a more complete (but more "research-oriented") version in MATLAB and a version with less options (but more apt to be used in production) in Java.

We can provide support (as time allows!) through [email protected] and/or GitHub issues system (https://github.com/goGPS-Project/goGPS_MATLAB/issues?utf8=%E2%9C%93&q=is%3Aissue%20is%3Aclosed%20).

Feel free to contact me if you have any question!

Eugenio

Thank you for your insightful answers.

  You can see  "GPS MATLAB Tools at Aalborg University by Kai Borre".