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Garmin Software

Last updated 0800 Saturday 3rd July 1999

GPS and PC

This page describes Garmin Software for those of you who have a Garmin GPS receiver. GPSS works with any GPS receiver fitted with a standard NMEA interface, but there are probably more Garmin receivers being used with GPSS than any other make. Mike Montgomery has kindly allowed us to put some of his software onto this web site, so that you may download it. This software supports the process of downloading track data collected in the GPS receiver, into your PC. This data can then be 'played back' using GPSS.

What Use is this Track Data ?

You can collect journeys made with only your Garmin GPS - including where you might not want to risk your expensive PC, such as hot air balloons, motor cycles, etc. You can then play it back on a map - but also e-mail it to others to play back. Robin finds this a practical way to test some of the overseas mapping, before he loads it onto the web site - and it's fun too !

What is Garmin GPS Track Data ?

By the time you read this, you probably already know that your Garmin GPS receiver can output two types of data on its computer interface :

  • NMEA data, typically every 1 second, giving position, course and speed. This is the data that GPSS uses to provide you with in-car navigation. This can be recorded into files of type .NME and played back by GPSS after your journey. You need a computer connected to the GPS receiver to record this data using GPSS, or other software such as Windows Terminal.
  • Track data collected within the Garmin GPS unit itself. Most receivers can collect over 700 positions in their memory. This may be based on time. e.g. every 10 seconds, or position : e.g. when you've moved another 300 metres. If this data is downloaded into your PC and given the file type .TRK, it can also be played back by GPSS.
NMEA data held in an NME file looks like this :

Track data held in a TRK file looks like this :
T N5206.71972 E00420.77637 16-OCT-96 17:54:11 -9999

Getting the Track Data Out of the GPS and Into the PC

The same computer interface cable that connects your Garmin GPS to the Notebook PC used 'on the road' can be used to connect it to your PC 'on the desk'. You may need a 9 pin to 25 pin adapter for the COM port of course. You will also need some software to download the data from the GPS into your PC.

Garmin supply software called PCX5 for this task. Unfortunately, they do not give it away - I believe it costs about 100 pounds in the UK. It is also relatively large (a megabyte) and complex to use. Luckily there is an alternative : GARDOWN from Mike Montgomery.

Garmin Software to Download Data - From Mike Montgomery

Dale DePriest in San Francisco kindly e-mailed me a program called GARDOWN that he had been using. When Robin checked the text file, he found that the owner was Mike Montgomery, also a Brit., and living just 30 miles away in London. So after a chat on the 'phone, and look at each other's web site, it was agreed to provide Mike's GARDOWN Garmin Software on this site. It is also available on Mike's web site for those into sailing.

GARDOWN.EXE is a self-extracting file holding two files GARDOWNA.EXE and GARDOWNA.TXT. Just run GARDOWNA.EXE from DOS for help.

You will see that to download collected track data into a file called BACKHOME.TRK you simply do the following from the DOS prompt :
- will download track data via COM2 into file BACKHOME.TRK

NOTE: Download latest version of GARDOWN from Mike's site if you do not want to edit the file as follows : Mike's old TRK file format was slightly different to that from Garmin, which GPSS handles. The lat/lon positions will still be plotted, but GPSS uses times to calculate speed. So, if you want GPSS to work perfectly, you will need to edit the TRK file to ensure there is a date and time in exactly the right place. You can do this with EDIT. So if the data from GARDOWN looks like this :
T N52 06.7197 E004 20.7763 Sun-Apr-20 17:54:11 1997
It can be changed to this :
T N52 06.7197 E004 20.7763 20-APR-97 17:54:11 1997
- by just doing an EDIT replacement of Sun-Apr-20 by 20-APR-97
Note that the month should be in upper case.

So here are the links to download GARDOWN *, email Mike, or visit his site :

DOWNLOAD GARDOWN.EXE (44,961 bytes) - * Old Version
GARDOWN.EXE self-extracts into two files, GARDOWNA.EXE and GARDOWNA.TXT, which are copies of GARDOWN Version 10 downloaded from Mike's web site. You may want to visit his site to take a later version. - Mike Montgomery's Sailing Web Site.
e-mail to Mike Montgomery - creator of the GARDOWN software.

Robin is grateful to Mike for making GARDOWN freely available to Garmin GPS owners.

Playing back the TRK files with GPSS

If you have files such as BACKHOME.TRK in the GPSS directory, you can play them back as follows:

  • Hit Q to tell GPSS to be quiet.
  • Hit Ctrl-A to display the Analysis Form
  • double click on the required file in the list
  • Click on the PLAYBACK button and watch.