les bureaux 
devient donc 
ortee de tous 
issociée à la 
ans avoir à 
udera à faire 
ie de barre à 
irs potentiels 
ogrammétrie 
el illimité. 
ignement du 
un probléme 
ammetry and 
lette, 1988. 
v Tool: The 
167. 
2. PC-Based 
s for Block 
ammetry and 
Redresseur 
Archives of 
S 
igital Image 
npany Inc, 
ry. PE&RS, 
NOVEL SOURCES OF CONTROL FOR AERIAL PHOTOGRAPHY 
A.P.R. Cooper’, R. Swetnam" and A.J. Fox 
British Antarctic Survey, Natural Environment Research Council, High Cross, Madingley Road, Cambridge, United 
Kingdom. 
"Department of Geography, The University of Edinburgh, Drummond Street, Edinburgh, United Kingdom. 
KEY WORDS: Photogrammetry, Block adjustment, Aerotriangulation, Shape-from-shading 
ABSTRACT 
Sparse survey control data have constrained large-scale mapping of the Antarctic Peninsula. Extensive aerial photography 
is available but photogrammetric techniques are difficult to use because surveyed points are very widely spaced. The 
presence of extensive snow-covered areas with insufficient surface detail to allow the topography to be followed in a 
stereo-plotter creates a further difficulty. In this study, control information was taken from various sources including 
georeferenced satellite images, surveyed points and airborne barometric surveys. A shape-from-shading algorithm allowed 
the elevation of snow-fields to be interpolated from barometric height information. These data provided control for the block 
adjustment of a series of aerial photographs. A horizontal accuracy of x60 m and a vertical accuracy of +15 m was 
achieved in a block of photographs containing only one conventionally surveyed control point. Such errors allow the 
construction of an internally consistent large-scale map for an area where inadequate control had restricted mapping to 
medium and small scales. 
INTRODUCTION 
  
Sparse control data and the presence of snow-fields with ^ 
insufficient surface texture for stereo-matching limit the 
usefulness of aerial photography in Antarctica. New control 
data are unlikely to be obtained because of the large areas : 
to be covered, difficult access and severe climate. These Alexander 
difficulties have limited the scope for large-scale mapping 
even in regions well covered by aerial photography. In 
coastal or mountainous areas of Antarctica the largest 
scale maps with extensive coverage are at 1:200,000 or 
1:250,000. To improve the quality of mapping in Antarctica, m 
it is necessary to find means of using the aerial 
photography. This paper presents new techniques for 
creating sufficient control for a block of photographs that 
only contains one survey point. The study area is located 
in the north-east part of Colbert Mountains, Alexander 
Island, off the west coast of the Antarctic Peninsula 
(Fig. 1). 
   
+“ ANTARCTICA} - 
  
  
  
    
  
  
  
   
[] 
Colbert 
Mountains 
   
DATA 
The data used in this study are from four sources: 
1) The study area contains one surveyed point in 
the British Antarctic Survey (BAS) triangulation 
network. This triangulation network was adjusted 
to fit Geoceiver positions acquired in 1975/76 
(Renner, 1982). The residual RMS error after this 
adjustment was +11 m (Knight, 1986). 
2) A Landsat TM image (scene ID 50719-12504 
acquired on 18 February 1986) covers the area. 
It is one of a mosaic of images that was block 
adjusted to fit the BAS triangulation network by 
the Institut für Angewandte Geodäsie (IfAG), 
Frankfurt, using the method described in Sievers image for the effects of surface elevation, using a 
and others (1989). IfAG have corrected the coarse digital elevation model (DEM) based on 
  
  
  
Figure 1: Location map for the study area. 
421