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Block adjustment
PHOTOMOD 6.0.2
1. Purpose of the document
This document contains detailed information about block adjustment procedure in
PHOTOMOD system’s window. Here there is a description of project types and methods
of block adjustment of both central projection images and scanner images, distinguishing
features of the methods, ways of adjustment accuracy control. The document also describes special aspects of adjustment of different images blocks and accuracy control
of various types of projects on stage of projects processing in.
2. General information
Block adjustment could be performed of both central projection images and scanner
space images.
The adjustment is a process of calculation exterior orientation parameters and coordinate
measurement of all points in the block.
It is necessary to have interior and relative orientation of block images available to start block
adjustment.
Block adjustment is performed after stage of data collection for phototriangulation, internal and relative images orientation, measurement of ground control points (GCP)
(see “Aerial triangulation” User Manual).
Minimal requirement for block adjustment is available results of interior and relative
orientation of block images.
For adjustment of images block it is necessary to preliminary setup of adjustment
parameters – specify coordinate system, select adjustment method, choose main adjustment parameters, setup report parameters and define residuals threshold of adjustment.
The system provides the following adjustment methods for adjustment of central projection images block:
• Initial approximation independent strips method or initial approximation using block
scheme is basically used to reveal blunders, such as incorrectly specified ground
control points coordinates, errors of tie points positioning, etc.;
• independent stereopairs method is used to increase accuracy of adjustment results,
obtained during initial approximation calculation; to recognize small errors and in
case of acceptable results, for final adjustment;
• Bundle adjustment is used for final block adjustment;
In many cases it is advisable to use independent stereopairs method and bundle adjustment
alternatively to recognize and fix small errors.
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