International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B2. Istanbul 2004 
amounts to a check-point accuracy of approximately 0.065 m in 
planimetry and (for a wide-angle camera) to 0.10 m in height. 
Thus, although the DMC has a smaller base-to-height ratio than 
a standard photogrammetric wide-angle camera and thus the ray 
intersection in object space is less favourable, the resulting 
accuracy potential in object space is still superior due to better 
measurement accuracy in image space and a better system 
geometry (flatness of the image plane, no film shrinkage etc.). 
It should be noted, however, that the reported results have been 
achieved based on imagery flown for a dedicated accuracy test, 
thus the actual values may be somewhat larger in production 
work. 
4.2 User comments 
[n user tests and in actual production work, a large number of 
DMC blocks were captured (see Table 2 for details). Flights 
occurred at various flying scales and over different terrain types 
and the project sizes varied considerably. Some of the blocks 
were flown with GPS and IMU. Different products were 
generated from these DMC blocks. In a highway corridor- 
planning project, images with a ground resolution of a few 
centimetres were acquired, and an orthophoto with a resolution 
of less than 0.1 m was computed (Table 2, A). 
In the following we report some results, obtained by various Z/1 
Imaging software products, from these blocks and also 
comments from users which they made while capturing and 
processing these data: 
“We consistently observed a standard deviation of the 
automatically generated image coordinates of 2 to 3 yum. 
resolution is nearly as good as modern film cameras show in! 
their system resolution calibrations at the USGS lab. In 
comparison with scanned film in softcopy, the DMC imagery is 
clearly superior, because it eliminates that extra scanning 
process." 
“In comparison with a film camera operation without in-house 
film development and film scanning capability, the DMC gives 
much faster turnaround, even though it does require a fair 
amount of time for imagery postprocessing.” 
“The DMC’s FMC capability gives it more latitude in terms of 
lighting conditions (cirrus overcast, poor contrast surfaces, poor 
reflecting surfaces, and time of year and day [but only if 
shadow length specs are relaxed ]). It provides a better S/N ratio 
by allowing more dwell time (longer exposure) on each pixel, 
or alternatively, faster speeds along the flight line." 
For orthophoto production the smaller base-to-height-ratio of 
about 0.3 (vs. 0.6 for a wide angle film camera) means that its 
imagery frames have an overall average closer-to-vertical 
viewing angle. This means more consistent radiometric 
response along strips and between strips. This helps to make up 
for its smaller footprint requiring more images per km? for a 
given pixel size in comparison with a conventional film camera. 
This also means less relief displacement: less lean is visible on 
features such as buildings and trees, and a less accurate DTM 
can be used to still satisfy ortho XY-accuracy specs. 
Unfortunately, the lower base-to-height-ratio may be a liability 
issue in the arena of 3-D contour mapping because it reduces 
the exaggerated relief effect that helps a stereo compiler to 
capture more subtle changes in ground elevation when 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
Project Name A B C D E F 
Project size (km^) 1.5 180 1150 2300 4100 1020 
Terrain Flat Urban Flat Urban Flat Urban Hilly Flat Forest Hilly 
Type Forest Mountain Urban Urban 
Rural 
Scale 1:3,800 1:10,200 1:11,450 1:21,600 1:43,250 1:21,600 
Pixel size, aerial 0.05 0.12 0.14 0.25 0.5 0.25 
image (m) 
AT o, (um) 23 2.3 2.5 2. NA 25 
Geo-Ref. Strategy | AT+ Control AT+ GPS AT+ GPS AT+ GPS GPS + IMU AT+ GPS 
RMS XY NMAS 1947! | NMAS 1947 | NMAS 1947 3m. 4m CE90* NMAS 1947 
RMS Z NMAS 1947 NA NA NA NA NA 
3-D Feature Planimetry No No No No Building 
0.3m contour 
line 
DTM Manual USGS DEM Automatic Automatic USGS DEM NA 
Delivery Product Pan Ortho + Colour Colour Ortho | Colour Ortho Colour, IR Building 
Mapping Ortho Ortho Polygon 
Pixel size, ortho- 0.075 0.12 0.15 0.3 2.0 0.25 
photo (m) 
  
  
Together with the very stable system geometry, these results are 
Table 2. Customers’ DMC Projects 
compiling a DTM for contour generation. 
Whether this will 
  
responsible for the fact that the DMC meets very high accuracy 
demands and seems to be able to support contour mapping 
down to a 0.3 m (1 fL) contour interval at NMAS 1947 
standards and maybe even to ASPRS Class I." 
“The DMC image quality is excellent, there is no graininess or 
fuzziness as is so problematic with scanned film, there are no 
scratches or other artefacts that occur on film, and the spatial 
have a significant effect on DTM accuracy is not yet known, 
but it is something that should be investigated. For now, we 
  
! Information about ASPRS standards can be found at 
www.fedc.gov/standards/documents/standards/accuracy/chapte 
r3.pdf 
2 CE 90 means 90% probability of a given point's coordinates 
falling within that circle's radius. 
400 
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