Downloading GPS Data

To make a gpsMap, you'll need to get your collected data out of the GPS receiver. You can recall each waypoint, write them down, and send us a list. No computer is required. Routes are also easy to transcribe by hand, but track data may be inaccessible, except through a computer interface.

The quickest and easiest way to get all of your data is to "download" it to a computer, then send us a diskette, or e-mail it with your order. To get your GPS data from receiver to computer, you'll need to buy or build an interface cable, and you'll also need a software package designed to "talk" with your particular GPS unit.

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Interface Cables

Most GPS receiver manufacturers can sell you a cable to connect your receiver to a personal computer. They'll also probably have a package deal, including software to talk with their GPS receiver.

Some manufacturers support only Windows or DOS computers. If you have an Apple, Palm, or other computer, you'll need to buy or build an interface cable, or just bridge the gap between the PC connector and a non-PC computer. The second choice can be easier, since GPS units may have unusual connection ports.

An adapter for the Macintosh is sold online at the GPSy (TM) web site. They also have references for making your own cables, and a complete software package for the Mac.

In any case, be careful! Whether you buy or build, connecting cables is risky. Problems can arise from voltage differences or pin-assignments. You could end up with no communication, or worse - a damaged computer or GPS receiver! Always connect cables with both units off.

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Interface Software

There are many GPS-related computer programs available for DOS, Windows, and Macintosh. Some are free, some "shareware", and some can be bought from the GPS receiver manufacturers, with or without an interface cable.

Once you've installed the software, be sure to set up the "preferences" for your communications port, the GPS unit you are using, and your preferred coordinate system.

Be certain you set the datum before downloading your coordinate data. USGS Maps will almost always use "NAD27 CONUS".

The software could possibly use the datum specified by your receiver, or it may default to "WGS84". Normally, there is a separate datum setting in the software.) A grand mess can be made of your data if you aren't careful about datum!

If you're not sure about the datum, try looking at a downloaded waypoint file on your computer, as described in the next section. If you see the same coordinates as your receiver shows when set for the same datum, all is well.

If you get coordinates, but the datum is wrong, translation from one datum to another is provided by several software packages, or we can translate for you. Be sure to specify the original datum when placing your order.

Waypoint & Track Data

You may be able to examine and edit your downloaded GPS data using a text editing program, like WordPad on Win95 or SimpleText on the Mac.

Your coordinates may be degrees, degrees / minutes, degrees / minutes / seconds (DMS), or meters on the UTM grid. Below, the first line is a waypoint in UTM, and the second line is DMS. Both have a name, date, and time.

CHEWSR 26-MAR-98 23:28 10 S 0628241 4019392
CHEWSR 26-MAR-98 23:28 36°18'46.2" -121°34'17.5"

Track data has date, time, and coordinates for multiple points along your path. The track points below are in UTM, but other formats are fine.

03/28/1998 21:46:40 10 S 3848257 0773326
03/28/1998 21:46:51 10 S 3848261 0773319
03/28/1998 21:47:02 10 S 3848261 0773315


You can store your waypoints in a spreadsheet, collecting thousands from all over the world. You can do tricks with tracks, like averaging multiple passes, though this is much more difficult than averaging waypoints.

Of course, we can do all this for you. Just say what you'd like done. We'll do a test plot, and adjust as needed before the final map is made.

NEXT: You can go to our Map Hints, information on gpsMaps, or the Wild Home page.

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