Garmin Custom Maps with G-Raster

Create Garmin Custom Maps with G-Raster
Creating your own maps to upload to the Garmin Colorado, Oregon, and Dakota hand-held units.
This review is based on using the Dakota 20 ° 23 Jan. 2010
8 Feb. 2010 -Add de-collar feature of v. 2.6
26 March 2010 -Add Working with Scanned Maps
11 June 2010 -Add Free Solution to the TVA DRG Map Problem
Return to Home Page ° Text by jack yeazel
For specific questions about this product, log onto the GPSInformation.net FORUM

GENERAL: Garmin claims you can create Custom Maps in five easy steps (HERE). 'Your mileage may differ,' but using Google Earth to create Custom Maps was a time-consuming pain for this reviewer. For the serious hiker, it seems that the USGS 1:24,000 DRG topo maps would be the most useful and legible on the GPS screens. Google Earth isn't especially helpful in converting these maps to the required .kmz maps needed for the Garmin units.

Eventually I came across G-Raster which has an ability to import the georeferenced DRG .tif files and export them as a series of smaller georeferenced .kmz map files. The DRG GeoTiff feature is fully free; you only need to pay $5 to allow you to input KMZ image overlay files created in Google Earth and tile them for export, and even then only for images larger than 1500 x 1500 pixels.

Click on these thumbnails for larger views
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Load Georeferenced File Auto Rescale Image Create KMZ File

PROGRAM SETUP:
Exporting the data files as .kmz files to the Garmin unit is easy as 1, 2, 3.

NOTE: This procedure has been updated to incorporate the ability to de-collar the DRG maps for seamless map connections in update version. 2.6. One must update the complete install (and not just the 'fixer') to get the latest Help files explaining the new feature.

1. Open a Georeferenced "USGS 1:24K NAD-27 Topo Geo Tiff" (DRG) map from the drop-down menu.
2. Auto Rescale will reduces the number of Tiles (maps) from 36 to 25, allowing one to upload four DRG maps to the GPS unit.
The number of "Tiles" (maps) is shown in the Info area to the right.
3. Create a KMZ file. The KMZ file will appear as a .kmz extension to the original filename in the source folder.
Upload this file to the GPS \Garmin\Custom Maps. NOTE: You can follow the progress of the program in the DOS prompt icon in the tray.

RESCALE:
Apparently G-Raster by default creates 40-something maps per DRG map WITH collars. Therefore only two DRG maps can be viewed by the Garmin at a time due to a 100-map limit. Setting a Rescale Factor of "1.5" produced only 20 maps/KMZ and a usable resolution of 3.67m/pixel (below), allowing uploading five DRGs. Loading the de-collared maps and using a Rescale of 1.3 cuts the Tiles down to 16, so that you can fit 6 de-collared topos on your Garmin. One should experiment with Quality and Rescale to suit their own situation.

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Full resolution at 20 Quality Rescaled at "1.5" and 80 Quality ° Here borders are trimmed Four maps joined at corners
(Notice loss of contrast in shot #3 due to Dakota upgraded to Ver. 2.60, and contrast restored in shot #4 with Ver. 2.61Beta)

SOLVING THE BORDER PROBLEM IN OTHER WAYS:
-Not the one in Texas. The USGS Seamless Server, MicroDEM, and USAPhotoMaps can remove the collars which allows one to upload more maps.

I have had the best luck with USAPhotoMaps, because not only is it a great GPS map and aerial photo display program, but downloading USGS 24K topo maps requires you only to push the F (Fill) key! The program has a feature to combine all the small geo-referenced (200 x 200 pixel) cells into one "BIG jpeg" file that G-Raster can read (from the drop-down list of supported file types.) I use a Quality of 80 on these files, because the 24K ones are at 4m/pixel instead of the usual 2.5m/pixel from the DRG maps.

SOLVING THE TVA DRG MAP PROBLEM:
If you use TVA-produced DRGs in GIS and mapping applications, you may already be aware that the TVA couldn't be bothered to add GeoTIFF information to its raster files like the USGS does with its DRGs. The TVA was kind enough, however, to provide world files (*.tfw) and metadata files (*.met). Many GIS applications can use the world files and/or metadata files, but some applications cannot properly georeference the DRG without GeoTIFF information included in the DRG.

From the link below, you can obtain a copy of the TVA DRG Repair Tool. The TVA DRG Repair Tool is a Windows-compatible program that combines a TVA-produced DRG with its companion world file and metadata file to create a new DRG that contains the GeoTIFF information required by many mapping and GIS applications. http://home.hiwaay.net/~taylorc/toolbox/gis-mapping/tva-drg/

WORKING WITH SCANNED MAPS:

Thumbnails
To create .kmz files of scanned maps requires a (free) intermediate program:

Image Georeferencer to do the registering
Note that the coordinates must be in UTM meters. 1. Load a UTM .jpg, tif, png, or gif map to be registered.
2. Select "Zoom" to enlarge the image at known points for more accuracy.
3. Select "Pan" to move the map around to bring into view three known UTM points
4. Use "Select Points" to mark each of three known UTM-coordinate points.
5. Either check or uncheck the "Rectify..." box. (You may have to experiment to get the best results).
6. Press "Georeference".
This will create a .jgw World File to go with the map file. If you check the "Rectify" box, " _Rectified" will be added to the map name.

In G-Raster

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Select UTM File from the drop-down list. ° Load file and add the Zone, Datum, and Hemisphere ° Press: Create KMZ File
A .kmz file should be created in the folder with the map file.

Some Scanned-map Examples
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Tracks around my home ° The scanned map adjoins three adjacent DRG maps

WORKING WITH LAT/LONG MAPS THAT HAVE NORTH-UP:

These maps will not register correctly unless the following steps are taken.
1. Determine the Lat/Long orientation of a UTM map of the same area
2. Rotate the Lat/Long map to the same orientation with something like Photoshop Elements.
3. Create Lat/Long waypoints at three map corners with G7ToWin -or any simular program that can convert Lat/Long to UTM coordinates.
4. Convert the waypoints to UTM NAD-83 coordinates. (WGS-84 gives the same results).
5. Run Georeferencing Tool with the rotated map using these coordinates to create a World File. (It doesn't seem to matter whether the Rectify box is checked or not).
6. Run G-Raster in the UTM mode, load the georeferenced map, set th UTM Zone, Datum, and Create the KMZ file

Thumbnails

Result in Gogle Earth.
Note that the Google Earth green line (denoting a river) follows the river in the scanned map pretty closely

Now don't get lost out there -youall!

jack yeazel