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.....
