The Challenges and
Joys of Mapping
America’s Last
Frontier
An interview with Dr. Dave Maune,
Project Manager for Alaska Statewide
IfSAR Mapping
Although all other states had USGS 1:24,000-scale topographic quad maps produced to National
Map Accuracy Standards (NMAS) as well as large-scale orthophotos refreshed every few years
to modern digital mapping standards, Alaska has never had statewide orthophotos, and its
1:63,360-scale topo quad maps from USGS did not satisfy NMAS for several reasons: (1) lack of
cloud-free stereo imagery; (2) lack of photo-identifiable ground control; and (3) because photogram-
metric block triangulation and GPS technologies hadn’t been invented yet when USGS produced
Alaska’s quad maps many decades ago. Recent attempts to produce digital orthophotos by draping
satellite imagery over DEMs from the National Elevation Dataset (NED) failed because the NED
was too inaccurate to support orthorectification, as demonstrated by Figure 1.
Figure 1.The NED’s low-res 60m DEM had horizontal errors
as large as one mile in the Brooks Range, shown here.When
draping satellite imagery over a DEM from the NED, some riv-
ers flowed uphill and not through valleys as they should. Image
courtesy of UAF GINA.
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202
April 2020
PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING
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Why was Alaska never previously mapped to National
Map Accuracy Standards?
