Getting a CAD file on a GPS

March 26, 2012 7:49 AM

Is it possible to install a CAD file into a consumer handheld GPS?

I've got a large site I need to look at this week before the client gets here, but the problem is the grading plan is not staked yet, and won't be for two weeks. I've been sent a CAD file (in dwg and dxf formats as well as a pdf), but I don't have AutoCad or any real working knowledge of it, and only just downloaded DraftSight and QuantumGIS, which I'm also pretty unfamiliar with. I've got a Garmin Etrex 20 which does allow customizable maps, but I don't know what the hell to do to get the CAD file georeferenced and scaled somehow to function on there in a manner that I can explore the site and stay close to the actual grading limits.

posted by Red Loop to Technology (6 answers total)

I'm no longer a CAD expert, but I would think without having the dwg scaled and georeferenced you might be borked. The only way I know of to do that is within AutoCad.

From there though you have to make the leap from a dwg file to whatever format the Garmin likes. Googling might help.
posted by Big_B at 8:49 AM on March 26, 2012

ExpertGPS sounds like it will work and they offer a trial version.
posted by JJ86 at 9:16 AM on March 26, 2012

Though you can get vector map data into Garmins, it's fiddly; OpenStreetMap have been all over it with OSM Map On Garmin. The difficulty, though, is more with CAD; AutoCAD file formats are really hideous to move around, and getting them into GIS usefully is an exercise in frustration.

What I do is:

1. Plot out the drawing to a decent-sized bitmap; it doesn't have to be huge, just enough to pick out the details
2. Georeference the bitmap to WGS84
3. Make a point layer, and add points pretty much in the centre of the areas you are interested in. Give them useful names so you can refer back to the map when you're on site.
4. Export that layer as a GPX file, and import it into your GPS.

Yes, it's not quite answering the question, but it an approach I've been using in the field since 2005, and it works for me. You might also want to ask on GIS - Stack Exchange.
posted by scruss at 9:40 AM on March 26, 2012

If you just need a few points, use a free DWG viewer to get the (state plane) coordinates of a few key locations. Corpscon will convert them to latitude and longitude, which you can enter into your GPS.
posted by Uncle Jimmy at 9:47 AM on March 26, 2012

Do you have access to an iPhone? There is an app called AutoCad WS that might help you.
posted by brorfred at 11:51 AM on March 26, 2012

Response by poster: I ended up exporting the file as a png file and overlaying it on Google Earth, and then saving it as a kmz file. It was fiddly to overlay, because it apparently doesn't have proportionate scaling, but it worked out fairly well in the end. I had seen expert GPS and I think I could get it to work, but it was looking like a more difficult prospect. Thanks for the help though, everyone.
posted by Red Loop at 11:22 AM on March 28, 2012