Utility programs for manipulating GPS and map data

I have several utility programs for manipulating GPS and map data.  The utilities are all 32 bit DOS programs intended to be run from a DOS command prompt.  Because the programs are 32 bit, you need a 386 or newer processor and a DPMI server.  Windows 3.1, 95 and 98 all provide a DPMI server if you run the program from a DOS window.

The utilities are distributed compressed in zip format.  All of the programs are copyrighted.  You may use and redistribute the programs for noncommercial use as long as the original "readme.txt" file is also distributed.  Please contact me regarding commercial use of these programs.

Please Email me at peteb@mailbag.com if you have any questions about or problems using these programs.

GPS track reduction

Pltred.exe reduces the number of points in a GPS track log.  The parameters used to reduce the points are controlled by the user.  A distance is used to control how far off the reduced track can be from the original track.  An optional angle parameter may be specified to reduce the "cutting corners" effect that happens when reducing some types of track logs.  The default for the angle is 90º.  Endpoints of track segments are always kept.  Points in the track log are never moved.  The programs just deletes excess track points.

This program is useful any time you want to upload old tracks or map data to your GPS receiver.  It is not uncommon to see the number of track points reduced by a factor of ten without a significant loss of accuracy (keeping GPS errors in mind).

Pltred.exe works with OziExplorer format track log files (.plt).  If you need other formats I suggest looking at g7to.  G7to will convert several formats to .plt format and back again.  It is easy to put g7to and pltred into a DOS .bat file so the conversions and reductions can be done by running one command.

A typical command line is:

pltred sag.plt 50 45 >sagr.plt

The track file sag.plt is reduced.  The program tries to keep the reduced line within 50 meters of the original track.  If a turn of more than 45 degrees is detected, track log points on both sides of the turn are kept regardless of their distance off the original track.  The output file is sagr.plt.  Sag.plt is not modified.

Download pltred.zip
 

GPS waypoint reduction

Wptred.exe reduces the number of waypoints in a file.  Any waypoint within a specified distance of a previous waypoint in the file is deleted.  The user controls the distance.

Wptred.exe is most handy when, for a given map scale, waypoints are just too close to be printed without overlapping.   For example, unreduced waypoints may look good printed on a 1:24000 scale map, but may be too close when printed on a 1:100000 scale map.  I also use wptred.exe to clean up waypoint files that I have generated automatically from map data in various formats.  Sometimes automatic generation of waypoints produces way too may points too close together.

Wptred.exe works with OziExplorer format files (.wpt).  G7to can be use to convert many different waypoint files into .wpt format.

A typical command line is:

wptred sagpe.wpt 250 > sagper.wpt

Any waypoints in sagpe.wpt closer than 250 meters to a previous waypoint in sagpe.wpt that has not been deleted  is deleted.  The output file is sagper.wpt.  Sagpe.wpt is not modified.

It helps if you can sort the waypoints in the original file so that the most important to you are listed first.  This wptred.exe keeps the waypoints listed first in preference to waypoints listed later in the file.

Download wptred.zip