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Systems for data processing, anaylsis and representation

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for contouring 68°57’ 68°55’
1 / o ’
© A 70°:30S
to e Insufficient data
for contouring
Insufficient data
for contouring

Insufficient data
for contouring

Figure 3 A map of a part of the Colbert Mountains, Alexander Island, Antarctica. The contour interval is 25 m. Exposed
rock is shown by grey shading.
The block adjustment was carried out using the BLOKK
suite of programs provided with the CARTO Instruments
AP190 analytical stereo-plotter. Several combinations of
the control points were used to find the optimum selection.
The best results have an RMS error of x60 m horizontally,

58°57 98:551 68:53" 70°32

Figure 4 A map of the same region as fig. 3, compiled from
satellite imagery at 1:250,000 scale in 1978.
and +15 m vertically. The various combinations of points
used are shown in Fig. 2, and the corresponding errors in
Table 1.
The lowest errors were obtained from test 1, which only
contained 6 control points. Although this is more than the
minimum number required to control the block, the
distribution of control points is weak, particularly in the
lower left quadrant. Test 2 used all the available control
and thus improved the distribution of points. Unfortunately,
the error is much higher, suggesting that some of the
control points are in error. Test 3 was designed to
investigate the accuracy of the points derived from the
shape-from-shading algorithm. This gave very good results
but the distribution of control is unacceptable since the left-
hand end of the block completely lacks control. However,
the low error figures, especially in the vertical dimension,
shows that the shape-from-shading algorithm has proved
reliable. Test 4 attempted to add control to the left-hand
side of the block and the poor result shows that some of
the points in the lower left corner must have large errors.
This is the only test where the vertical error is
unacceptable. Test 5 used all the points with
measurements in three dimensions, and the result is
comparable with that from test 3; it gives a better
distribution of control but the lower left corner is still
unsupported. Tests 6 and 7 represent attempts to
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The output
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25 m, can
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Dr. J. Sieve
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Mrs J.W. '
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University o
project, whi
Knight, J.A.
Antarctic €
Antarctic SL
36 pages [|
Mcintyre, |
altimeter: In
p. 1775-17¢
Rapley, C.(
Birks, A.R.
Cooper, A.F
Huckle, H.t
Milne, K., |
Scott, R.F.,
study of sat
surfaces: E
Renner, R.
network ov
Survey Bull