International Archives of Photogrammetry and Remote Sensing, Vol. 32, Part 3W14, La Jolla, CA, 9-11 Nov. 1999 
  
Unit Price 
(USS/km) 
. s10 
  
DEM Cost vs Vertical Accuracy 
Vertical Accuracy (m) RMS 
Increasing Detail —» _U 
  
  
€ 
BÖGEN 
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jeter 
  
  
  
  
  
1 
  
  
  
Figure 2: Relative Unit Costs for various DEM extraction methods 
This table illustrates the relationship between cost to the 
user and the spatial ‘detail’ provided by the particular 
technology. In this instance, vertical accuracy is used as 
the metric for detail although more correctly, one should 
use a three-dimensional metric that incorporates sample 
spacing or posting as well as vertical accuracy. Also 
shown for comparative purposes are DEM prices derived 
from a number of other sensors, including: (i) Radarsat 
and SPOT stereo at a lower level of accuracy but lower 
price and (ii) aerial photography which is competitive 
with laser-derived DEMs. Unit prices reflect many 
factors including size, complexity, location and other 
project specifics, so this table is rather general. However, 
the trend shows that interferometric SAR provides a 
price advantage of 3 to 10 times that of laser-derived 
DEMS on a price per unit area basis. This table does not 
address minimum project areas or mobilization charges 
which tend to be related to geographic location specifics. 
Moreover, it reflects current pricing structure which is 
likely to change over time. 
The ‘Global Terrain’ prices are noted to be lower than 
project-specific prices, reflecting a ‘data warehouse’ 
approach that was initiated two years ago by Intermap. 
The concept, similar to that widely practiced for satellite 
imagery, is to license DEM data to the user, hopefully to 
re-sell multiple times. While this reduces the price for 
the user, its utility is subject to there being data available 
in the database for the particular user area of interest. 
6. EXAMPLES 
6.1 Red-River, North Dakota 
The project area was near the Pembina river, a tributary 
of the Red River which has a history of flooding in the 
US and Canadian portions of the flood plain. An area of 
about 4,000 km? was acquired by the STAR-3i system on 
or about November 3, 1998. Within this larger area, a 
subset of laser data were acquired by EarthData on 
October 27, 1998 and made available to Intermap for 
analysis. Both data sets were referenced to WGS-84 
horizontally and the NAVDSS geoid vertically. The 
STAR-3i data were posted at 5 meters while the laser 
data were received as 3 meter ArcGrid files. The 
vegetation had been removed from the laser DEM by 
EarthData, so the data received was in the form of a bald 
earth DEM. All data (in this and the following 
examples) were analyzed using a commercial software 
package (Vertical Mapper from Northwood Geosciences, 
Ottawa) which is very convenient for doing comparative 
analysis. The particular area subset for this example is 
centered on (N 48° 38°25", W 979 27 53"). An 
overview of the laser DEM (Figure 3) shows the 
overlapping area, the flight lines and the window within 
which the following figures are located. 
The sub-areas of Figure 4, Figure 5 and Figure 6 are co- 
registered and have identical color table representations. 
They depict, respectively, the laser DEM, the radar DEM 
and the difference surface (radar minus laser) on a 3 
meter grid. 
  
  
Kilometer 
  
Figure 3: Lase 
study area 
The laser DEM 
the radar has | 
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Figure 4: Las 
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