Elastic Adjustment Program:- uses Least Squares Principle and
variation of coordinates technique to adjust a list of coordinates to
better fit up to 50 fixed positions
The program can accommodate a 3D model for shift, height, rotation
and variable scale.
Preparation is straightforward with a text file of the coordinate listing
being edited to include comparative values for fixed points.
A weighted adjustment is calculated for each unfixed point dependent
upon proximity to all fixed points.
The model produced is contorted with all fixed points remaining with
exactly their original values whilst other points are rubber banded.
Note that the program is not intended as an adjustment for actual
observations rather as post processing to improve the fit.
quote : 'rubbish in ... beautiful out'
The program was developed to repair the relationship of the base
cadastral plan of Dora Creek Sewerage Project to the as-constructed
survey measurements.
The base plan was a mosaic of manually entered Deposited Plans with
errors approaching a metre(!) over the 20 square km. apparent from
closed survey to original survey marks.
By filtering the base plan through this adjustment the survey
measurements were not compromised and the relationship of sewer
infrastructure to boundaries was less than 0.2 metres specified by the
construction Authority.
As this type of adjustment caters for variable scale within the model
rather than producing an overall best fit the original lot dimensions
were essentially preserved within local areas according to survey
marks found.
The program works in conjunction with other CAD software
(e.g.CivilCAD, MicroSurvey etc.) when lines rather than points are to
be adjusted. The method in this case requires points to be
permanently attached to all lines. An ascii output of all points from
the CAD software is generated and then filtered through the Elastic
Adjustment Program - the resultant ascii file is then reimported into
the CAD software altering the point values and hence line positions.
more.....
