Local Trail MapThere’s so much going on with Garmin Custom Maps right now it is hard to keep up!  Here are some more tips, tools, resources and limitations we’ve learned about today that we would like to pass along.  If you have discovered your own please post them here or over on the wiki discussion threads linked below.

Tips

  • To combine multiple JPEG images into one KMZ file create a directory in Google Earth and copy or add your individual overlays into the directory.   From the directory select Save Place As to store the KMZ to your GPS.
  • You can have a \Garmin\CustomMaps folder on both your SD card and internal memory.
  • KML/KMZ uses WGS84 datum but an image can be in any datum as long as it can georeferenced and reprojected (warped) to WGS84
  • Draw Order >= 50 will make the an image show up above any installed Garmin maps (see first image below)
  • Draw Order <50 will make the image show up on top of the land areas of installed Garmin maps (i.e. land, lakes) but the Garmin map data like roads, contour lines, etc. will show up on top of the custom map (see second image below)

High Draw OrderLow Draw Order

  • Custom maps with a higher Draw Order will draw on top of those with a lower Draw Order
  • Waypoints, tracks, routes, geocaches, POIs, etc will always draw on top of Custom Maps
  • Putting the map page in North Up mode makes map updates much faster and if you’ve referenced maps that are oriented north up the labels are easier to read
  • Custom Maps don’t appear in Automotive orientation.

Tools

  • GPSVisualizer Overlay KML (see my previous post for detailed instructions on how to use this)
  • GlobalMapper (not the free trial version, the $280 version) does a good job creating KMZ overlays.
  • MapTiler (0pen source and free!) which is based on GDAL seems to have most of what we need but it uses superoverlays which are not supported.  Add a vote here to have them add support for Garmin Custom Maps!
  • gCensus-gt, I haven’t tried it but it looks useful for converting a variety of file types into KML, but it too may only support superoverlays
  • Tiler for ExpertGPS. I’m trying to contact the author of ExpertGPS to see if the tool could be modified to create files in the format we need

Resources

Limitations / Bugs

  • No support for multiple custom map layers on the GPS which you can enable and disable separately
  • Each individual image should be smaller than 1 megapixel, larger files will render but at a reduced quality
  • No single image should be larger than 3MB (per Garmin) because of the time it takes to render
  • You can have multiple images in a KMZ, but the GPS is limited to a total of 100 JPEGs across all KMZ files
  • As a rough rule of thumb if you want good resolution down the 300′-200′ zoom level the limitations above will mean you can only have a maximum of about 100 sq/miles of imagery loaded
  • Only JPEG images are supported
  • Google Earth superoverlays are not supported
  • Colorado users are reporting that the current tracklog shows up as wide magenta line over the overlay maps.  Garmin has indicated it will be fixed in the next release.
  • I’ve seen cases where the tracklog and waypoints stop getting drawn after zooming in/out on a large custom map (still less than 3MB)

Related posts:

  1. Tips on Garmin Custom Maps – Using GPS Visualizer
  2. Tips on Garmin Custom Maps – Getting Started
  3. Tips on Garmin Custom Maps — GPS Visualizer Adds Garmin KMZ Support
  4. Garmin Custom Maps Officially Available on Oregon, Dakota and Colorado
  5. Garmin Beta: Custom Raster Map Support for Oregon, Colorado and Dakota