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Exporting GPS Data To GIS I – Garmin GPS Units



Geodetic-quality GPS units are usually able to output data directly into a GIS-friendly format like shapefiles, either with built-in software or with add-on packages like Trimble’s Terrasync or ESRI’s ArcPad. But what if you have a consumer-grade GPS unit without the ability to run this software (or you don’t feel like coughing up hundreds of dollars to buy a copy)? This post and the next one will cover some options for downloading data directly from a GPS and converting it to the GIS-friendly shapefile format. First up – an easy solution for Garmin GPS owners.


If you’re using a Garmin GPS unit to gather data for GIS, you have to get a copy of DNRGarmin. Minnesota’s Department of Natural Resources produces this tool, and has generously released it for use by the general public. While it can connect with any serial GPS unit via the NMEA interface for position measurements, it can only download waypoints, routes and tracks from Garmin units, and there are a few Garmin units it won’t work with (e.g. the iQue series). But it should work fine with the vast majority of Garmin units past and present, and it supports both serial and USB connections.

After downloading and installing the program, hook up your Garmin unit to the your computer, turn it on, and run the program. DNRGarmin should determine that you have a GPS connected; if it doesn’t, go to the GPS menu, and make sure the right port is selected. Once the GPS is recognized by the program, you can go to the Waypoint, Track or Route menu to Upload data from your GPS. Here’s a screenshot of DNRGarmin after a set of tracks has been uploaded:

GPS track uploaded to DNRGarmin

The data table lists off all the combined track points that have been uploaded, with a track identifier and position for every one (altitude as well if it’s a 3D fix). You can modify, or even delete, individual track points in the data table.
Shapefiles come in three basic varieties, point, line and area/polygon, with each type only able to hold data of a particular type. In other words, if you have a point shapefile, you can’t put lines or areas into it. While that holds true for saving data in DNRGarmin in shapefile format, you do have a choice of what format you save data in. Suppose you have a track that describes the perimeter of a particular area you’re interested in. If you download that track data, DNRGarmin gives you the option of saving the data in any of the three shapefile types:

  • Point – Every point in the track is saved as a single point vertex in the shapefile
  • Line – The track is saved as a line shapefile, with every track point as a vertex
  • Polygon (area) – The track points are treated as vertices describing an polygon, with the first and last points in the track automatically connected together to complete the polygon perimeter.

If you download a set of individual waypoints that describe a line or an area, you can also save those as a line or polygon shapefile as well. After downloading the individual waypoints, just select “Track” or “Route” from the radio buttons near the top, and DNRGarmin will let you save those points in line or polygon shapefile format (if you leave the radio button in “Waypoint”, you’ll only be able to save those waypoints as a point shapefile).

To create the shapefile, first determine which points you want to save as the shapefile. If you have multiple tracks, for example, and only want to save one track in its own shapefile, you could delete all the points from other tracks that you don’t want. But DNRGarmin also lets you select sets of points in the data table; if any points are selected, then only those points will go into the shapefile you create.

Next, go to File => Save To => File, and select shapefile from the “Save as type:” dropdown box. You’ll have two options, unprojected and projected. Unprojected will create a shapefile in the WGS84 geographic coordinate system, latitude and longitude; projected will create a shapefile in whatever coordinate system and datum you’ve specified in File => Set Projection menu (default is WGS84, geographic). If your GIS can handle projection on the fly, or if it has a shapefile coordinate system converter, you’re probably better off saving shapefiles in DNRGarmin in unprojected form. If the Track or Route radio buttons were selected, DNRGarmin will now let you choose whether you want to save in Point, Line, or Polygon shapefile format; if Waypoint was selected, it will automatically create a point shapefile.

If you’re not familiar with shapefiles, I should note that a single “shapefile” actually consists of at least three files, with the .shp, .shx, and .dbf suffixes. The .shp contains the position data, the .dbf contains information about every shape (e.g. name, altitude, etc.), while the .shx is an index file that connects the two. DNRGarmin also creates a fourth file, with the .prj suffix, that describes the coordinate system and datum associated with the shapefile. Some GIS software can read this .prj projection file automatically and use it to assign the right coordinate system to the shapefile.

Here’s a screenshot from a GIS that has a shapefile created from a GPS track using DNRGarmin, laid over a USGS topo for the same area:

shapefile converted to GPS track
DNRGarmin comes with a first-rate help file; there’s also an excellent PDF manual available from the US Forest Service on how to use the program. DNRGarmin is so good that if you’re thinking of buying a GPS unit for use in acquiring data for GIS, it could be a major factor in determining which brand of GPS you buy. In the next post, I’ll talk about options for other brands of GPS units, and you’ll see that it takes more steps, and is a bit more difficult, to get their data into GIS format than it is with Garmin units using DNRGarmin.

Addendum: Hey, I forgot to point out that if you have ArcGIS 8.x or 9.x, you can use DNRGarmin as a plugin to these programs for direct import of GPS data. See the DNRGarmin website for details.





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19 Responses to “Exporting GPS Data To GIS I – Garmin GPS Units”


  1. 1 askan

    Your blog is still at the very high level you started with. Congratulations.

  2. 2 Matt Priour

    We have been using this software for years at my company. We really like it a lot and it is critical to our workflows. The software has continued to increase in quality & features and is a rather impressive bit of work. I don’t know where we would be without it.

  3. 3 Chaz

    I love this program, use it all the time. Another great program I use is GPSMapEdit http://www.geopainting.com/en/
    It lets me upload parcel data to my Garmin. Great cheap GIS substitute.

  4. 4 Leszek Pawlowicz

    GPSMapEdit is a great program with many capabilities; I use it regularly to create high-resolution (10-meter-contour) topo maps for my Garmin. Biggest problem is the lack of documentation. For one or a few parcels, it’s probably easier to upload shapefile data directly to your GPS as a track, which I’ll cover shortly.

    I may do a series on rolling your own Garmin maps some day …

  5. 5 Chaz

    Leszek,

    mapwel
    does the same thing as GPSmapedit but not free.

    As for documentation on GPSmapedit your right on, there is not much out there. I did it all by trial and error. But now it takes me about 5min to convert a .shp for use on a garmin.

    Here is my most recent project.
    Land Trust Preserve Map

  6. 6 Leszek Pawlowicz

    MapEdit isn’t completely free – you have to pay to get a full set of features, and you also have to pay for and register the complementary program cgpsmapper to get the full feature set from it as well.

    For your map, you recommend using img2gps, the GUI for SendMap. Using Sendmap or img2gps isn’t an ideal solution, since it doesn’t allow you to combine your custom .img file with Garmin’s map files, and wipes out any map data already uploaded to your GPS. mapwel’s free upload program supposedly lets you add your .img map file to those already uploaded, but it doesn’t seem to work that well for me. I’ve wound up adding my custom map info to Garmin’s MapSource program, so that I can upload both my custom maps and Garmin’s standard maps together.

  7. 7 chaz

    True GPSMapEdit fully featured its not free. But if all your going to do is slap some polygons/polylines with labels on a GPS its free. Also, In my situation Im trying to distribute custom garmin map data to the masses who are not so smart, I need as few steps as possible. Thus img2gps, simple load file and send. Also in the maps I create I include Roads, rivers, lakes exc.. So hopefully users will not need Garmins data. The data Garmin has for my area is not that good.

  8. 8 Anonymous

    Is there anyone out there who has the pdf from the ftp site? I have tried to download it for a week and can not get my hands on it. If so you can mail it to me: patrick.brooijmans@tiscali.nl

    Thanks!

    Patrick

  9. 9 Leszek Pawlowicz

    Patrick,

    Link works fine for me, so I’m not sure what the problem is. I’ve emailed you a copy of the file.

    Leszek Pawlowicz

  10. 10 Thomas

    Can GPSMapEdit send tracks direckt to a Garmin GPS?

    “But if all your going to do is slap some polygons/polylines with labels on a GPS its free.”

    Or is MapSource nedded?

  11. 11 Leszek Pawlowicz

    GPSMapEdit creates an .mp file, and then uses cgpsmapper to create a .img file. You can send this .img file to a Garmin unit without MapSource by using a program like img2gps (a GUI for the command-line SendMap program):

    http://homepage.ntlworld.com/mdipol/img2gps/

    MapWel also has a free program called MapUpload that will do the same with a few types of Garmin units:

    http://www.mapwel.com/

  12. 12 Thomas

    Thank you Leszek!

    Then GPSMapEdit is not what I search for.

    I need a program that will upload SHP files to a Garmin GPS.

    DNRGarmin seems ideal but it will not eat the shape files I need it to. Without processing an error on the GPS (I tried everything) .

    Do you know any alternatives?

  13. 13 Thomas

    I found a solution. GPS TrackMaker will load my shape files.

    http://www.gpstm.com/index.php

    Very nice program!

  14. 14 Leszek Pawlowicz

    I did a post a while back about importing shapefile data into a GPS, and GPS Trackmaker was my first choice:

    http://freegeographytools.com/2007/importing-gis-data-into-a-gps-unit

    DNRGarmin will work, but you have to make sure you have the projection set correctly. If you try to import shapefiles in UTM coordinates, you have to set the projection to the correct UTM zone and datum. If you don’t, DNRGarmin may take the UTM coordinates to be latitude/longitude, which would create errors on your GPS. If you’re importing a line shapefile and want to turn it into a track with DNRGarmin, you also need to know that it will convert all of the lines into a single track file, and load it in as the active track; you’ll have to save that active track under its own name if you want to keep it separate from the active track.

    GPSMapEdit will import shapefile data, and convert it into the standard Garmin map format (.img). This is useful for those cases where you have more than 10,000 points in your tracks, since this is the typical track point limit for many Garmin units.

  15. 15 Thomas

    Thank you for clearing that up Leszek.

    It is the active log that has been teasing me.

    It was your “Importing GIS Data Into a GPS Unit” that showed me GPS Trackmaker.

    It is way more advanced then DNRGarmin. But GPS Trackmaker cannot export a shape file as you point out.

    You and your site have been very helpful.

    /Thomas

  16. 16 Andy Anderson

    One problem with DNRGarmin which prevents its use in laboratory situations: you must have administrative privileges on the computer where it is installed in order to use it with USB-connected Garmin GPS receivers. The problem has been there for at least a year, and they acknowledge it on their web site, but it doesn’t seem to be a high priority to be fixed.

  17. 17 Thomas

    This bug is just been fixed:
    “you must have administrative privileges on the computer where it is installed in order to use it with USB-connected Garmin GPS receivers.”

    2/13/08 — Version: 5.3.2

    Bug Fix:

    * USB Connectivity now works for users without ADMIN rights to their computers.
    * Automation Error (#-2147467259) when saving to a File Geodatabase — Fixed.
    * RLIDENT field will now save up to 15 characters (previous limit of 10)

  18. 18 Thomas

    New update released.

    DNRGarmin GPS Application

    Current Version:
    ArcView Extension: 5.4.0
    VB Program: 5.4.0
    ArcGIS Toolbar: 5.4.0
    Build Date: 9/11/2008
    Posted Date: 9/11/2008

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