At the Alaska Surveying and Mapping Conference in 2008,
I used ASPRS’ DEM Users Manual (that I authored/edit-
ed) as a reference, explaining why the topographic layer is
foundational for producing orthoimagery and other mapping
layers. The DEM Users Manual explained the need for es-
tablishing DEM requirements first -- prior to deciding what
DEM technology to use. Alaska then hired Dewberry to
produce the Alaska DEM Whitepaper. Contrary to my lidar
recommendations elsewhere, the Alaska DEM Whitepaper
recommended aerial IfSAR statewide for Alaska because
our requirements analysis indicated that DSMs and DTMs
with 20’ contour accuracy satisfied known statewide require-
ments, including immediate aerial navigation and safety
requirements of the Federal Aviation Administration (FAA),
and because IfSAR could meet this requirement while map-
ping through persistent clouds. Alaska then asked USGS to
contract with Dewberry to execute statewide IfSAR mapping
under its USGS GPSC contract.
Figure 2. Looking up at Denali (20,310 ft.) from the base camp
at 7,000 ft. from which 4 surveyors traversed ~83 miles hor-
izontally and climbed ~6 miles vertically (including back-and-
forth caching) while carrying over 700 pounds of equipment
each year to the peak to perform GPS & GPS surveys in 2015
and 2016. Image courtesy of CompassData.
Despite the logistical challenges in GPS surveying IfSAR
prism reflectors and QA/QC checkpoints throughout vast
remote areas of Alaska, the Dewberry team knew that we
could do the job technically, but we didn’t know how much
it would cost or who would pay for it. I authored the Alaska
DEM Funding & Implementation Plan that recommended
cost sharing among multiple federal and state stakeholders,
and Dewberry worked with its two IfSAR subcontractors to
submit a technical proposal to USGS. We estimated it would
cost $77.3M to map Alaska over a 2-year period, with Fugro
EarthData mapping the most-difficult 23% of the state using
its GeoSAR system, and Intermap Technologies mapping the
less-difficult 77% of the state using its (three) STAR systems.
Fugro’s perceived advantage was that the GeoSAR included
both X-band and P-band; combined with GeoSAR’s lidar pro-
filer, the P-band should be better able to map DTMs through
dense forests, but Fugro did not have a mature production
line for doing this. Intermap’s advantage was that it had pro-
duced NEXTMap®Europe, NEXTMap®Britain, and NEXT-
Map®USA over 49 states; it had a mature production line for
delivering standard products that exceeded USGS specifica-
tions for mid-accuracy DEMs, even though it used algorithms
to estimate vegetation heights for production of DTMs from
X-band IfSAR that maps top reflective surfaces (DSMs).
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“A Government cannot do any
scientific work of more value
to the people at large, than by
causing the construction of proper
topographic maps of the country,”
by John Wesley Powell, 2nd Director
of USGS, in his testimony to
Congress on December 5, 1884.”
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Why was Dewberry selected to
solve Alaska mapping problems?
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What were your initial challenges?
