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GENERAL: 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.
G-Raster 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. NOTE: One can change a .kmz file extension to .zip and see the contents of the file.
Click on these
thumbnails for larger views
Load Georeferenced File Auto Rescale Image Create KMZ File
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.
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.
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
-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 georeferenced 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 GOOGLE EARTH PHOTOS:
TerraIncognita can convert Google Earth, Google Streets, Bing, myTopo, and OziExplorer maps to a SINGLE ArcView .jpg map. (This allows one to brighten and sharpen Google Earth photos with Photoshop, so they can be improved when converted to Garmin Custom Maps.)
NOTE: G-Raster can only handle up to 100 megapixel maps. First determine that the ArcView map is less than this size. The file demensions are in the bottom left-hand corner of TerraIncognita,
1. In G-Raster, select "EPSG File" from the drop-down menu. 2. Select "Load EPSG Raster With Worldfile.". 3. Select the .jpg file made by TerraIncognita. 4. Insert "EPSG Code" of 3395. 5. "Process Raster Graphic" (Eventually, you'll see part of the .jpg). 6. Do "Auto Rescale" (The number of tiles (on right) will be less). 7. "Create KMZ".
NOTE: Reducing the number of tils allows you to keep within Garmin's Custom Map limit of 100 tiles
WITH THE NEW USGS NATIONAL MAP GeoPDF TOPO MAPS:
These maps are freely available at the USGS Map Store for downloading. The maps are in a .pdf format where one can select various overlays to be viewed. Such as, Contours, Hydrography, Transportation, Boundaries Geographical Names, Projection and Grids, and Orthoimages (aerial photos).
G-Raster v. 4.2 now has under Tools, a GeoPDF Tool, that can convert the .pdf to a georeferenced .tif file. The default resolution of 250dpi resolution can be changed to about 350dpi for some improvement in image quality without exceeding Garmin's limit of 100 tiles. NOTE:The file should be loaded as a "USGS 1:24K WithCollar" in order to strip off the collar.
Run "Auto Rescale" before creating the KMZ file in order to reduce the number of tiles below 50. The file can then be converted into a .kmz file suitable for uploading to Garmin units that support Custom Maps. Each .tif and .kmz file is a complete 7 1/2' Quad.
Using a decollared 250 dpi map, the total tile count drops to 30; using "Auto Rescale" drops it to 20. Set the rescale factor to 1.4, and the tile count drops to 16, which lets you put 6 USGS Quad topo maps onto your Garmin. Obviously, the higher the rescale factor, the lower the map resolution, especially noticeable on the aerial imagery.
The GeoPDF Tool (as-is) doesn't let you turn layers on and off directly, but there is a rather complex workaround in Help, "GeoPDF Tool Limitations". The aerial photos are not as detailed as Google Earth photos, but in rural areas, they are more equivalent. The USGS plans to increase image resolution for all maps over the next few years, after it gets the first set done.
National GeoPDF Topo Map .kmz map superimposed on Google Earth ° Native underlying Google Earth map
WORKING WITH SCANNED MAPS:
Some Scanned-map Examples
Tracks around my home ? The scanned map adjoins three adjacent DRG maps
WORKING WITH LAT/LONG MAPS THAT HAVE NORTH-UP: