Download Aerial triangulation

Aerial triangulation
PHOTOMOD 6.0.2
Recommended values lie in range from 90 to 95%. In contrast to all other filtering criteria,
this parameter directly influences on operation of points measurement and transfer. Check
for exceeding of correlation threshold is performed only for new points (if there are already
measured points). To check all measured points for exceeding of correlation threshold (usually,
at final stage of collecting measurements of tie points) set the additional Delete points with
correlation below threshold checkbox on the Rejection tab in the additional parameters
window.
• Maximum vertical parallax (in pixels or mm) – threshold value for rejection executed
after points measuring/transfer. On each step of rejection process, the program
searches for the point with maximal Y-parallax on the stereopair and rejects it. After
that, it makes relative orientation once more and the iteration is executed until maximal Y-parallax exceeds the parameter specified here, or until 6 points or less remain
on stereopair. Recommended value is a pixel size;
• Maximum error in triplets in XY-plane and by Z (in pixels, meters or mm) – threshold
discrepancy of points measurements on adjacent stereopairs in triple overlapping
zone of adjacent images in a strip. Use the following formula to calculate values of
acceptable errors in triplets:
E max ≈ 2 E mean , where E mean – acceptable mean error.
Mean triplet errors in XY plane is calculated using the following formula:
RMS ≈ 2 E mean
Mean error by Z equals the mean error value in XY plane multiplied by the ratio of
focal length (f) to survey basis (b):
z
E mean
=
f
b
xy
E mean .
• Measure points by zones – allows to apply a method of sequential measurement
by zones of overlap area. If the checkbox is cleared, points search is performed over
the whole area of images overlap. The system allows to select zones and define their
size in the Zones section on the Miscellaneous tab of the additional parameters
window;
• Filter points by zones – is used to filter points in stereopair zones sequentially;
The operation provides filtering the worst (by parallax) points on stereopair, passing zone by
zone one after another. So the worst point on stereopair is found and deleted first, then the
worst one in the next zone and so on. Uniformity of point’s distribution on stereopair is also
verified in such a way.
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