updated: 24-Mar-2011

 Copan for Windows

Field FreeStations Processing

Contents
  1. Process Field FreeStation Data
  2. Field FreeStation Data Entry
  3. Field Files
  1. Field FreeStation File Example
  2. FreeStation Calculation Method
  3. Notes

Use this module to process raw free station surveys — horizontal and vertical circle readings, slope distances, and instrument and signal heights — based on setups at unknown points and radial shots to known points. Data can come from total station files, data logger files or be manually input. Free stations (or modern resections) are calculated using the best-fit of angle and distance shots to (up to 10) control points. Resulting setup points and side shot points may be saved. Multiple free station surveys can be processed in a single session.

Note that classical resections (involving angles only), intersections, traverses, and two-faced (FL & FR) observations are not handled here. (For intersections, use the § COGO Calculations module. For ordinary traverses, use the § Field Data Processing module and for bearing traverses use the § Field Bearings Processing module.)

Also note that, while there are certain similarities between the Map Traverse and the Field Data modules, there are various operational differences (other than the type of map/survey data involved). If you are familiar with one and new to the other, please study the appropriate manual and dialog carefully.

1. To Process Field FreeStation Data

From the Calculation menu, choose Process Field FreeStations.

  1. Calculation | Process Field FreeStations...
  2. Optionally Load... a Field Data File. (See § Field Files.)
  3. Edit data in the big edit box as required. NB: To move the text cursor: Use the arrow, Tab, or Enter keys, or the mouse pointer. To manually insert a tab, copy and paste an existing one.
  4. To enter setups and observations data, use the mini edit boxes and the relevant Insert button. To enter project, instrument and scales data, use the supplementary dialog via the More data button.
  5. Optionally Export.. the Field data file in (the BitWise Ideas survey network least-squares adjustment program) GeoLab IOB format.
  6. Save the Field file for reuse.
  7. Optionally change the precision of displayed/listed distances and coordinates via Settings....
  8. Optionally Scale extended-code sizes. This will scale any observation P-codes that are sized according to the rules in § Point Codes by a Units Factor you have set.
  9. Calculate (or OK) to process the field data, accepting the calculations as appropriate.
  10. To graphically view the shots: Close the Info Display window if it is open, and minimize or move aside — but do not close — the Field FreeStations window.
  11. Optionally List the field Data, the Calcs, or the Points that have been computed.
  12. Optionally choose whether to Renumber new points or replace existing points (see § Point Renumbering or Replacement) and Save the Points that have been computed.

To process field survey data: enter setups and observations in the boxes at the bottom, and click Calculate.click for larger view

2. Field FreeStation Data Entry

Setups and Observations Data Entry

Project, Instrument and Scales Data Entry

Keep these three types of data on separate lines: Be sure to use the proper correction. In most cases, the default values are appropriate.

3. Field Files

Copan can read field data in different industry formats as well as its own. A native Copan field file consists of numerous Setup and Observation data lines and may contain comment lines, as well as Project, Scale, or Instrument data lines, if required. Each data line consists of various tab-separated attribute = value pairs. See § Field Files for a description of different raw field file types and Copan's field file format.

4. Field FreeStation File Example

In this example, codes and notes have been omitted for brevity. The survey from setup 19 is a 3D freestation to three control points followed by two side-shots. The survey from setup 21 is a 2D freestation to three control points followed by two side-shots.
at= 19                                                    HI= 1.7
        to= 84   HC=  0.0000   VC= 89.0005   SD= 27.566
        to= 85   HC= 85.2920   VC= 88.3020   SD= 19.040   HS= 1.2
        to= 86   HC=139.0800   VC= 88.0105   SD= 24.950   HS= 1.2
        end= resect
        to= 91   HC=111.2155   VC= 91.5835   SD= 10.120   HS= 1.2
        to= 92   HC=123.4405   VC= 90.2705   SD= 15.950   HS= 1.2
at= 21
        to= 86   HC=  0.0000   VC= 84.5950   SD= 13.904
        to= 85   HC= 85.0720   VC= 86.4505   SD= 16.355
        to= 83   HC=137.1830   VC= 82.3930   SD= 19.641
        end= resect
        to= 95   HC=299.4800   VC= 91.0740   SD=  8.180
        to= 95   HC=302.5440   VC= 92.1310   SD= 11.833

5. FreeStation Calculation Method

The 2D portion of a freestation is calculated is as follows:

  1. Treat each control point's horizontal circle reading as a temporary bearing and, with reduced distances, compute temporary local coordinates for each control point relative to the setup point.
  2. Determine the best-fit rigid-body transformation, by least-squares, of the control points from their temporary to their actual coordinates and show the residuals.
  3. Transform the setup point using the estimated parameters.

Assuming the appropriate elevations and heights are present, the 1D portion of a freestation is calculated is as follows:

  1. Compute temporary local rises for each control point relative to the setup point.
  2. Determine the average rise and show the residuals.
  3. Transform the setup point using the estimated rise.

6. Notes

updated: 24-Mar-2011