How All Topo Base Maps are Produced
AllTopo base maps are sourced from:
No matter the source, the All Topo Professional Map Series (the products in the 11" x 6" boxes) maps are 250 DPI, UTM projected, raster image files. All Topo V6 mapping products (the products in the 5" x 6" boxes) are 160 DPI maps.
Converting a Paper Map into a Digital Scan
1. First we inspect the paper map for stains, dirt and anything that will scratch the glass on our scanner. Often we find 'blobs' of wax that are left over from the cutting shear that sizes the quadrangles after printing.
Both sides of the paper map are blown off and dusted. Some maps require hand cleaning to remove background dirt that accumulates while the maps are stored on shelves.
2. Next the paper map is scanned on a Graphtec CS2000 large format color scanner at 600 DPI to a RLE (Run Length Encoded) Bitmap using a standard palette. It takes about 1 minute and 15 seconds to scan each sheet and save the 'raw' image to disk:
Each scanned image occupies about 250 megabytes in memory and has plenty of (perhaps too much) detail:
3. After each page is scanned we open and inspect the previous scan for wax-smears or scanning problems while the next image is being scanned. We can scan 45 maps per hour and will often scan 50 to 250 maps in each batch.
4. After an entire batch is scanned, we use a proprietary program to:
This metadata is collected for each file in a batch process, it takes about 1 minute to enter the metadata for each raw scan.
5. The raw map image and the metadata for each map scan in the batch are compressed to a ZIP file and archived on DVD. This process is started and completes overnight without any human intervention. The DVD's are only used if we loose a drive or need to generate a 500 DPI raster image under contract for another supplier.
6. A batch process is performed to convert the raw map scans to finished raster images. This process:
The color normalization process is very import. We want all the greens, all the reds, all the blues (hydrologic) colors to be the same color. This allows the AllTopo viewer to remove the vegetation (green) layer, or highlight hydrologic features. It also results in the exact same color of green being used on every AllTopo map nationwide.
It takes about 4 to 10 minutes to process each image on a 3GHz machine.
7. After the batch conversion is complete, each of the images is viewed again. During this final inspection, we can nudge the grids and coordinate information around the map to fine tune the coordinates that AllTopo reports when the map is viewed or exported.
This final inspection is performed on the actual binary file that we will include in our map sets and on our internet based updated map server.
Here is the fully processed North East corner of the sample map scanned above:
8. The final 'All Topo Map' is published to the internet updated map server and archived on our terra-byte server for inclusion in future map sets.
Map Comparisons Between DRGs, FSSE and Igage Scans
All Topo Map Professional Reference map sets include all of the map revisions that we have in our collection. Users may select which map revision they want to use in the viewer and seaming tool. All maps may be used hillshaded (3D) or un-hillshaded.
All of these sample maps are from base maps included in the 'All Topo Maps V7 Professional Map Reference Set' SKU 673654-385849; MSRP $180.00.
These comparisons are made at the confluence of Green River and Red Creek in Daggett County Utah; Goslin Mountain and Clay Basin quadrangles. Not every map in the map set will have multiple revisions available.
Forest Service Single Edition Quadrangles:
Continue to > [ Comparing Igage scans and Competitor's scans ]