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Generation of Cost Effective Digital Image Base Maps from the Ikonos
and QuickBird Commercial Satellites
Elected officials within local governments require timely information
products to support policy decisions on issues that are often interrelated
and can span several political boundaries. A digital image basemap
is a key information layer in many local government GIS systems. Image
basemaps are used by city planners and engineers for tax assessment,
inventory, construction planning (roads, bridges, etc.), stormwater
management, and other civil planning activities (greenbelt preservation,
E-911, etc.) A major stumbling block to the effective application
of remote sensing imagery within local government is the positional
accuracy of the imagery. Our interaction and discussion with basemap
users within various local government user communities indicates that
planar accuracies of 3-5 m CE90 are required for 1-m resolution digital
basemaps to be useful for GIS applications. The recent launch of Space
Imaging’s Ikonos and DigitalGlobe’s QuickBird satellites
has opened up a new arena for acquiring up-to-date high-resolution
panchromatic digital imagery for use as digital orthoimage basemaps.
The Carterra Geo Ikonos product costs $21/km2, but its horizontal
precision is poor with a planar accuracy of only 50 m CE90 (Space
Imaging, 2000). While this product is affordable for most local government
entities, the planar accuracy of 50m CE90 renders this product unusable
for traditional basemap applications. The Carterra Precision Ikonos
panchromatic image product costs $63/km2 and has a planar accuracy
of 4 m CE90 (Space Imaging, 2000). While this meets the planar accuracy
requirement for basemap implementation, it is three times more expensive
than the Carterra Geo product. This cost can be prohibitive for many
local government entities with limited fiscal resources. The challenge
then becomes to develop a methodology that would enable the use of
the lower-cost Carterra Geo products for creation of digital basemaps.
We have developed and demonstrated a methodology to generate highly
accurate orthoimage basemaps from the lowest cost commercial high-resolution
satellite imagery. The methodology uses a limited amount of ground
control (8-10 GCPs per image), 30-m resolution USGS DEMs, and Commercial
Off The Shelf (COTS) software to orthorectify the lowest cost, lowest
precision commercial high-resolution satellite imagery. The methodology
is equally applicable for both the Ikonos and QuickBird commercial
satellite imagery. We have performed rigorous assessments of the horizontal
accuracies of the resulting image basemaps. We have quantified the
effects of DEM horizontal resolution and vertical accuracy on the
resulting horizontal accuracy of the orthorectified image basemaps.
Results from multiple test sites have shown that we can routinely
produce digital image basemaps with horizontal accuracies of 2-5 m
CE90. The methodology we have developed can be used to deliver up-to-date,
cost effective orthoimages from the lowest cost Ikonos and QuickBird
image products that yield horizontal accuracies suitable for use as
digital image basemaps by local governments.
For further information contact: Curt
H. Davis, 323 Engineering Bldg. West, UMC, Columbia-MO, 65211. Email:
DavisCH@missouri.edu Tel: 573-884-3789.
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