DeLorme File Formats

DeLorme's mapping software for the PC is quite powerful. It allows you to create, log, and display a great deal of map information beyond what they already provide. The problem is that the file formats they use are proprietary, and DeLorme is not talking. To help other people who want to be able to extract the information they created with one of DeLorme's programs, I decided to create this web page containing the things I have discovered.

Updates & Revisions

DeLorme GPL File Format

This format is used by DeLorme Map'n'Go 3.0 and Street Atlas 4.0 to store GPS tracks. The file is composed of equal length records. Each record is 56 bytes long.

The format of the record is:

* The C 'time_t' format stores both date and time. The stored value is the number of seconds since January 1, 1970.

The following 'C' structure can be used to access the data in each record.

struct GPL_Data_Point
    ULong       status;
    ULong       dummy;
    double      latitude;
    double      longitude;
    double      altitude;
    double      heading;
    double      speed;
    ULong       time;                           // in <time.h format
    ULong       dummy3;


Here is a BASIC (Quick Basic) program to do the same function. It was written by Tom Hammond (, and called "GPL2ASC". The source for this version can be found here.

The ReadGPL Package

This is the complete package of utilities for manipulating GPL files. It includes several tools for doing everything from translating GPL files to and from ASCII Text, to manipulation of the time and speed fields.

The Zip file containing just the executables and some samples is no longer available. The Windows executables are included in the source distribution and can simply be copied wherever you like (only the *.exe files are needed!). A Zip file containg the entire source code along with the executables can be found in the file

Note: This is basicallly the same version as before, but I have changed compilers so that people can computer for which gcc (the free GNU C Compiler exists. I have also added functionality to GPL2VRML and ReSpeed commands, and I have written a new program that converts from CetusGPS files (recorded on a Palm) to GPL files. See the "readme.txt" file for more details.

Feel free to use it for any non-profit cause (i.e. school, church, personal). If you decided to use it as part of another program, modify it, or redistribute it, please keep the copyright information and my name with it. I must first approve use for commercial ventures. No warranty is expressed or implied as to its ability to work correctly. User beware.

Sample GPL Files

I have repackaged the sample files so that they are both contained in a common zip file. Both tracks are in Rochester, NY area. One is a fairly small track taken over lunch. The other is a long track of a day long TSD rally. The samples can be found here.

These track files were made with a DeLorme Tripmate.


Other Links

*Peter Bennett's FTP Page - a great GPS Resource
*CetusGPS GPS Interface for your Palm
*My Home Page *The Snow Tire FAQ, one of my other passions.


If you have any updates, corrections, or comments, please feel free to send them to me at

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