Glenn Baddeley - GPS - Garmin GPS38 Information


[Glenn's GPS Contents Page]


Now Obsolete

The GPS38 became quite a popular receiver following its release in February 1996. It was seen as a lower cost replacement for the GPS40, with improved software. The '38 was retired from the market by Garmin in 2000. As a single channel receiver it could no longer compete with the many multi-channel receivers which became available at reasonable prices.

This also means that the GPS38 is readily availabe on the used GPS receiver market for a very cheap price. It makes an ideal entry-level or experimental unit.

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Straight from the sales blurbs...

The GARMIN GPS 38 is the one navigational tool for the great outdoors that offers big features in a small, lightweight package - all at a truly affordable price. Mark your favorite fishing spot, tree stand or camp site or retrace your step back to the safety of your truck using our all new TracBack feature. The GPS 38 shows you exactly where you are, where you've been and where you're going.

The GPS 38 features easy, one-thumb operation and weighs only 9 ounces. There's a resettable trip odometer, graphic compas and highway steering guidance. And it provides up to 20 hours of use on a set of 4 AA batteries. The GARMIN GPS 38. The affordable way to bring you back.

Basic Features


* Subject to accuracy degradation to 100m 2DRMS under the United States Department of Defense-imposed Selective Availability Program.

Physical Specifications


Navigation Features

** Speed Limitation GARMIN products designed for non-aviation use will display a maximum speed of approximately 90 knots or 103 MPH. This unit will not display speed or position information if this limit is exceeded.

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NMEA sentences

Here is a list of the group of NMEA sentences transmitted by the GPS38 in its two NMEA 0183 output modes The sentences are transmitted in this order every 2 seconds approximately. A link is provided to a description of the format of each sentence.

NMEA 0183
NMEA 0183
Code Contents
YES YES $GPRMC Recommended Minimum Specific GPS/TRANSIT Data
YES YES $GPRMB Recommended Minimum Navigation Information
- YES $GPGGA Global Positioning System Fix Data
- YES $GPGSA GPS DOP and Active Satellites
- YES $GPGSV GPS Satellites in View (transmitted twice in each group)
- YES $PGRME Estimated Position Error
YES YES $GPGLL Geographic Position, Latitude/Longitude
YES YES $PGRMZ Altitude Information
YES - $GPXTE Cross-Track Error, Measured
YES YES $GPBOD Bearing, Origin to Destination
- YES $GPRTE Routes (not transmitted in every group)
YES - $GPBWC Bearing & Distance to Waypoint, Great Circle
YES - $GPVTG Track Made Good and Ground Speed
YES YES $GPWPL Waypoint location

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The End-Of-Week-Rollover problem

After 22nd August 1999 the internal week counter in some Garmin GPS receivers (including the GPS38) rolls back to zero because it has insufficient precision to count beyond a certain value. If the GPS receiver firmware is not updated to a new version the unit will experience slow acquisition of satellites and take a long time to get a fix on its position. This is because the GPS receiver thinks it is in a different week to the real week and it will attempt to use the wrong ephemeris data to locate satellites.

There is a Windows PC GUI program which will update the GPS38 firmware via a serial port cable connected to the GPS receiver:

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GPS38 Links


Copyright © Glenn Baddeley 2005, 2014 was last updated 6 July 2014.
Report problems and send comments to Glenn Baddeley.