Instructions for 3D Coordinate Adjustment [ ELASTIC.EXE ]
- These may be in any order, but must be separated by spaces with decimal points in alignment.. no tabs allowed
- Fields recognised are:-
Easting, Northing, Height, PointNo, Comments, Code
The comments field can be used as an empty dummy field or to separate the field codes
Any line with the first character being a semicolon will be treated as a comment & ignored,unless the 2nd character is 'F' (uppercase) in which case it is considered to be a FIXED POSITION.
The FIXED coordinates are entered on the line above the relevant RAW coordinate
These values can be interspersed thoughout the file or at the start for readability.
e.g:-
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This screenshot shows the edited raw data file now containing FIXED POINTS flagged by '
;F' as the first 2 characters in a line:
i.e. Point #500 = #1 Fixed
#513 = #17 Fixed
#524 = #5 Fixed etc. |
The Program transforms the list of coordinates as follows:-
- 1 Fixed Point: SHIFT in Easting, Northing & Elevation
- 2 Fixed Points: SHIFT, ROTATION & LINEAR SCALE
- 3 or more Fixed Points: SHIFT, ROTATION & VARIABLE SCALE
When completed a further file ( outputname.err) is created showing all point adjustments. This should be perused to satisfy yourself there are no gross errors. The thing to look for is similarity in
values of diffE, diffN & diffH for the fixed stations which indicate the degree of rubber-banding.
Depending on the purpose of the adjustment you may need to remove FIXED points that have excessive shifts.
When editing in the Fixed Points the program expects values for Easting, Northing & HEIGHT. If Heights are not valid for certain fixed points then process the adjustment twice.. once to ascertain
values for horizontal position - then edit this adjusted file to include heights & reprocess.
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This is the .ERR File that shows Rotation, Shift & Scale
Also shown are the small differences for Easting Northing & Height:.... Note the similarities of dE & dN for
the control points:
Then follows a listing of adjustments to all points in the file. |
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The Program adopts the first FIXED point encountered & compares distances to all other FIXED points. It then uses the furthest FIXED point to determine an initial SHIFT, ROTATION & SCALE for
the model. These values are shown in the .ERR file. The SCALE of the model is therefore relevant only for calculation purposes & is in fact VARIABLE once there are more than 2 fixed positions.
The Program comes in 2 parts .... ELASTIC.EXE which is invisible to the user & SETPARS.EXE which is the program interface: ELASTIC.EXE will not run alone. The command structure is DOS based
with ELASTIC being a parameter of SETPARS.
e.g. :- c:\[directory]\setpars c:\[directory]\elastic
I keep my data in a directory c:\survey\data & DOS programs in c:\dos\sys which from the DOS prompt appears thus:-
C:\SURVEY\DATA> C:\DOS\SYS\SETPARS C:\DOS\SYS\ELASTIC runs the program.
When you first run the program another file column.tmp will be created which maintains a default columns settings.
COLUMN.TMP will be kept in the directory from where you run the program.
- Scans the input file for ALL FIXED POINTS.
- Selects 2 Fixed Points from which to SHIFT, ROTATE & RESCALE the entire model on a 2 POINT
TRANSFORMATION.
- STORES VALUES OF SMALL SHIFTS (dE, dN, dH ) FOR ALL FIXED POINTS against this 2 point transformation.
- For each UNFIXED POINT calculates distances to each FIXED POINT & determines the SMALL SHIFTS according
to least squares weightings of the sums of these distances.
- Outputs Adjusted File & Information File
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Please note that this program is not designed for adjustment of survey observations. It performs the adjustment as a whole regardless of from where the observations have been
made.
It is designed as a rubber-banding technique to improve a 3D model, preserving absolutely fixed point values instead of the conventional best-fit solution.
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