For those that might not know, there are two types of free topo maps that are both geo-referenced. The advantage of using geo-referenced maps is that you can add your own data, such as a GPS track, to the map.
The topo maps are tiff files. In order to make the geo-referencing stuff work you also need to download a metadata file that begins with the same file name but which ends in tfw instead of tif. You need to place both files (tif and tfw) in the same folder. Sometimes the map file and metadata file are compressed into a single zip file.
Of course you also need a program that can open these map files and do cool things with them (like adding GPS tracks). Here’s a list of freeware. No doubt there are others.
If you are really into futzing with maps, then you might want to check out the freeware GDAL utilities.
1. Sources for scanned 7.5ʺ quads
These are scans of the same paper maps you can buy from the USGS. They include all the map collar info.
* Forest Service (scroll down for link). Washington and Oregon topos.
You can define the area to be included on the map. If the area you define covers more than one 7.5ʺ quad, then the maps will automatically be joined together. The map data is the same that appears on the 7.5ʺ quads. However, there is no map collar info.
Joey’s Quick Start Guide for USGS Seamless Server:
1. Click USA map
2. Point-click-hold-drag to select an area that includes the area you want on your map
3. Click the icon in front of “Orthoimagery” (near right edge of your screen)
4. Check the box for “DRG Scanned Maps”
5. Adjust the map zoom so it is as zoomed in as possible while still including the area you want
6. Click “Download” near the upper right of your screen
7. Under “Elevation” - Uncheck 1" NED
8. Click the icon in front of "Orthoimagery"
9. Check the box for “24k DRG Zone 10”
10. Under “Downloads” (left edge of screen) - Click the first icon to “Define Rectangular Download Area”
11. Point-click-hold-drag to actually select the area that will be downloaded to you
12. A window will appear titled “The National Map Seamless Server Request Summary Page”. It should say: “Output Format: GeoTIFF NAD 27 UTM Zone ___”. Note that the map you will receive will be in the UTM projection and based on the NAD27 datum.
13. Click “Download”
14. In a few seconds you will be able to specify the folder where you want the downloaded zip file to be placed
15. Unzip the file
16. Open the tif file with whatever software you are using to work with geo-referenced tif files
NASA's World Wind 1.4 program includes USGS Topo Maps and USGS Digital Ortho, with whatever vertical exaggeration you want, etc.
Here's an example copied from World Wind:
Mount Baker Wilderness, Mount Baker - Snoqualmie National Forest, Washington State Taken from NASA's World Wind 1.4 program, using USGS Topo Map. 121.81986W_48.77479N
Thanks, Joey, for posting this link and your step-by-step tips!
Initially, it was a bit tedious learning how best to select a specific area but the outstanding results were worth the time and effort!
For less than $2, after using CutePDF to convert the .tif file to a .pdf doc, I plan to print the Topo map of Eagle Cap Wilderness (sized 11x17) using Fedex's online print services.
You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum
Disclosure: As an Amazon Associate we earn from qualifying purchases when you use our link(s).
