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How All Topo Maps are made
AllTopo base maps are sourced from:
- Paper maps, scanned and processed by Igage
- USGS Digital Raster Graphic products [ see Digital
Raster Graphics ]
- Forest Service Single Edition digital products [ see SEQ
]
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:
Click to view a portion of the raw image
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:
- set the map name, keywords (state list), date, scale
and destination filename
- 'pin' the four corners of each map and additional
coordinate control points
- set the process range (we don't need the over-scan
area in the output file)
- block out any map areas we don't want included (like
barcodes)
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:
- re-samples and rubber-sheets the raw image to 250 DPI
UTM projection
- normalizes colors to a standard palette
- compresses the resulting raster image into the .IP5
AllTopo file format
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:
Click for full resolution image
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.
USGS DRG:
Click for full resolution image
Forest Service Single Edition Quadrangles (FSSE)
Click for full
resolution image
Igage Scans:
Click for full resolution image
Continue to > [
Comparing ATM ]
back to All Topo
Maps V7 info
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