Garmin Protocol Information and Data Transfer Programs

Purple Computing (Larry Berg) has power and data connectors for Garmin 45 and similar receivers (38,40, II, 12xl...). He also shows a cable wiring diagram.

Ready made cables using Larry's connectors are available from Dave Sorenson

Garmin Protocol Description by John Waers (html format, 11388 bytes)

Garmin.txt (24018 bytes) is another description of the Garmin protocol, by William Soley and Eric Werme. (last update July 4, 1996)

Anton Helm has an updated version of the above file, describing new features in the Garmin protocol, inlcuding icons and display mode. Get it from his site

Gardown11 (57,568 bytes, rev. Sept./97) transfers waypoint, route, and track data between a Garmin GPS to a PC, and can log NMEA-0183 data. (MS-DOS) The latest version is available from the GarDown home page By Mike Montgomery (

Gardyloo.exe (88604 bytes Oct.4/97) converts track files from gardown to .DXF files for use with CAD programs, and .ASR files for use with Microsoft Automap Streets Plus (MS answer to Delorme Mapping). It can be used, among other things, to view a track on top of a US street map, or to enter a route an then follow it in a car. By A. Peter Allan (

GPSdb is a waypoint database program for use with Garmin receivers. It requires Win95 or WinNT. The program will upload and download waypoints, tracks, and routes. It will import from GarDown files. Waypoints can be created in this program and uploaded to the GPS. Routes can be created by "drag and drop". It also exports waypoints and tracks in Street Atlas format. Includes various map datums. More info and downloads at From Tim Hubbard (

GARNIX is an MS-DOS program to up/download waypoints, routes, etc. from a Garmin GPS . The package includes a program to convert between Lat/Long, UTM and other grids, and to convert datums.

Thomas Ott has a program called GPS2PILOT2PC . This program allows the USR/3Com PalmPilot to track transfer data to/from a Garmin GPS. The program can also make the Pilot look like a Garmin GPS to a PC, so the usual Garmin protocol programs can be used to transfer the track data between the Pilot and a PC (or Mac, I suppose...)

GARtrip is a new Win3.1/Win95 shareware program for users of a Garmin GPS receiver by Heinrich Pfeifer.

Main Features:

Available as either english version(489,030 bytes) or german version(501,061 bytes) (version 1.12 , Feb 12/98) (15,492 bytes) contains the source code for an Excell Add-in (VB for Apps) which converts GarDown7 track data to a *.dbf file, and converts the Lat/Long to the Swedish National grid.

GarLink vers. A.02.02 (1,168,986 bytes) is a windows program to transfer waypoints, routes, etc. between a Garmin GPS and a PC. It allows editing of the waypoints on the PC. The waypoint list is in the same format as used by WinGPS. To use this program you must either register it, or get a 4 month demo licence by writing to the author. The program was written by Peter Aigner (

Garm16.exe (for Win3.1, 308K, Jan 21/97) or (for Win95, 211K, July 28/97) is another program to up/download waypoints, tracks, etc. between a Garmin GPS and a PC. By Klaus Voigt (

gps75arc.exe communicates with a Garmin GPS75 or 45 (probably others) to upload waypoints directly by mouse click without switching the protocol of the receiver. From Michael Reiners (

Waypoint+ is a Windows95 program to transfer waypoints, routes and tracks between Garmin receivers and a PC. It will write the data as a text file, or in formats compatible with DeLorme Street Atlas 3.0 or 4.0, or Map Expert 2.0. By B. Hildebrand ( See the Waypoint+ home page for further information and to download the program (59797 bytes) contains the source code and design notes (including a description of the Garmin protocol) for John Waers' ( MacGPS-45 Macintosh program, which transfers waypoints, routes, etc. between a Garmin GPS and a Mac. This file has been converted to a DOS archive (and a MacWrite document converted to WordPerfect), but the program has not been ported to DOS. The original Mac format source archive and program are available from Please note that both these files contain the source for an early, somewhat buggy version of MacGPS. The current shareware version of this Macintosh program is available from (The version number is subject to change from time to time...) The commercial version of this program is available from

Karen Nakamura's "GPSy" program for the Macintosh (described above) now handles the Garmin protocol.

GPSTrans is a Linux program based on MacGPS. It will upload/download waypoints, tracks, routes, and almanac from a Garmin GPS. Written by Carsten Tschach ( This file contains "tarred and zipped" C source. Another version, with some additions or corrections is gpstrans-0.31b-js1.tar.gz (84,415 bytes), by Janne Sinkkonen ( (I'm told the -js1 version is for Linux, the other is for Sun/HP) Jacques Bouchard has an MS-DOS port of this program at

gd2: This C language program (inspired by GarDown) is designed to download tracks, routes, waypoints, position, clock, and almanac and to upload routes and waypoints from/to Garmin 12xl, Garmin 38 and Garmin 45. The package includes man page, makefile, and notes. It works well on Linux and FreeBSD, and needs help for SunOS. Available as a .shar file: gd2.shar (70662 bytes) or gzipped tar: gd2.tgz (18415 bytes) Oct. 21, 1997. By Randolph Bentson ( (53,423 bytes, Jan 22/97) contains some programs by Lance Rose ( to exchange waypoint data between a Garmin 45 (and probably most other models) and a DeLorme Street Atlas 3.0 map file (.SA3) using the Garmin protocol. They let you create waypoints with the map program and upload them to the GPS, or download the waypoint database from the GPS to a specified map file for later manipulation. converts GarDown7 download files to Street Atlas 3 format, or vice versa, and converts either format to formats compatible with PROJ.EXE, NAD2NAD.EXE, or UTMS.EXE. This version can also communicate directly with a Garmin receiver using the Garmin protocol. The C source code for this program is available as (83888 bytes). (31045 bytes) includes a program to capture NMEA-0183 data at user-defined intervals, and some batch files that semi-automate the conversion between the files captured with this program and SA3 files. Can be used in conjunction with g7to and gardown7. (by Richard Hess (46093 bytes) converts the data downloaded by gardown into a .dxf file for import into AutoCad or other drawing programs that read this format. (from (25925 bytes) is a shareware program to transfer waypoints, routes, track logs, etc. between a Garmin 45 (not tested with other models) and a Psion series 3A (10878 bytes) provides an interface between Mapinfo Desktop Mapping Software and a Garmin GPS receiver, using the proprietary Garmin/Garmin protocol. (from

Garmin Data Monitor (229905 bytes) uses the Garmin protocol to display information not available via NMEA-0183, such as satellite status, more precise position to display SA "wandering", etc. HPx00LX palmtop databases of waypoints and segmented road track logs fo rthe UK. The databases have been set up to allow their partial upload to a Garmin GPS45 with the G7TO203 program so you can get a relatively detailed moving map display on your GPS without exceeding its memory capacity. By John Seymour (