In Defense of the Garmin Personal Navigation Device (PND)
Merry Christmas and Happy New Year Everyone,
I thought this would be a good topic for those surveyors who love the ancient GPS gear that keeps on ticking. Over the years the GIS specialist of the world have gone through a ton of device and software transitions with a preponderance of workflows designed for GIS (ESRI) integration. In Alaska and with a strong focus on keeping things simple, the lowly Garmin still finds a place in our backpacks and in our surveyors vest as the cheapest, almost free navigation and simple point,line,poly storage device on the planet. Don’t let Garmin or GIS listserves get you down with overly complicated mechanisms to display, navigate too coordinates. Garmin and the folks at Minnesota DNR have the best suite of tools that can fortify navigation to points found on any website and do it with these main focus points:
1) low power consumption, AA battery power
2)Excellent datum handling between NAD83 and WGS84
3) Ease of data transfer via USB and older serial ports (on older models)
4) Cheap and simple to use with free DNRGPS and GeoSetter
5) Buttons for guys with big hands and gloves
6) Accuracy typically at 2 meters (don’t believe the hype of 5-10 meters)
Cutting to the chase on cost, a Garmin Map76 – $276 + MapSource Topo for maps ($35) free DNRGPS and a Pocket Card will set you back under $300.
Nothing in the modern suite of 38 Outdoor Garmin models can hold a candle to long deprecated Garmins like the Garmin 76, Garmin Map76C, Garmin Map76S, Garmin Map76CSx. C=color, S = sensors like barometer, X=Sirf Chip . The entire 76 line floats, incorporates Tides, Trip Computers and simple waypoint averaging, and track log setups.
As far back as the Garmin GPS 76 (last firmware 2005) the device has WAAS enabled (Do enable WAAS – default is NOT ENABLED). Ebay prices are around $276 . Disadvantage of going this far back is the 4-pin cable that requires serial interface with the PC. There is also no way to limit screen display on this older model. Otherwise a solid device
Stepping through the later models, Garmin Map76C, Garmin Map76S, Garmin Map76CSx you get increasing capacity including ability to limit screen displays and better compass navigation since you can switch between GPS and Compass navigation when standing still. None of these have GLONASS, but are otherwise plenty capable of navigation to the 2 meter accurately handled coordinates you feed using DNRGPS
DNRGPS is free and handles the error you will encounter when assuming you set NAD83 on the Garmin and your getting on-the-fly datum transformation. Your not. All Garmins use the Molendensky, 3-parameter transform which assumes NAD83=WGS84. Squeezing out this .9 – 1.4 meter shift is easily handled by DNRGPS which uses the NAD83 and ITRF96 shifter at epoch 1997.0 and exposes these parameters for your convenience. DNRGPS doesn’t throw away the incoming our outgoing coordinates either, allowing you access to either coordinate in Lat, Long, Xproj, Yproj fields in a multitude of agnostic formats including shapefiles. DNRGPS in conjunction with any of the 76 series absorbs all data using the Garmin Serial interface requiring a simple DLL to connect to any modern PC (Mac’s not supported). Excellent support too which includes the long history that I have been lucky enough to be involved with inside the Fire/SAR community. Check out the support page here which includes handy double-sided pocket cards that travel anywhere and maximize “GIS like” settings you won’t find on the Geocaching sites on the internet. Supporting fire crews with life-saving navigation was the crux of our training and support which has given way to modern GIS (ESRI) centric workflows, but in the day, we were all about Garmin/DNRGPS workflows that today still clearly supports a surveyor’s approach to using a simple device to navigate to a point, find your way out of the woods (using Garmin TRACKBACK) and creating KML,shapefiles,csv,GPX files for non-ESRI solutions. No internet and did I say 2 AA batteries?
Can’t say enough about the lowly Garmin. Pick up a Garmin Map76 model. Don’t forget to have fun too. This is the ideal book if you are teaching kids about all things geospatial. I’ve used dozens of these cool, mathematically challenging techniques exposed in the Fun With GPS book. Still on sale at amazon.com for $4.00. How cool is that?
Joel (with time on his hands with the shutdown).
Log in to reply.