Least Squares Adjustment Editor: File/Extract

(This functionality is available with the Adjustment module)
(Not available in LISCAD Lite)

Extracts control observations from a selected Field File into the currently open Adjustment Control File and displays them in the Least Squares Adjustment Editor.

Adjustment control observations, by definition, consist of the following types which may be extracted from a field file or entered directly:

Note: Any operations contained in the field file which would affect the resulting position of the extracted observation are not applied in the extraction process. Such operations include left/right offset and add/reduce distance. Do not use such operations on control observations.

The adjustment control observations may then be edited and adjusted using the least squares adjustment editor to provide adjusted co-ordinates of the control points in the data base. Then, when the field file is reduced using the Field Transfer/Resolve/Reduce Field File command, these adjusted co-ordinates in the data base will be used in preference to any co-ordinates found in the field file, ensuring that the reduction of the field file is in accordance with the adjustment carried out.

Extract Control File dialog box

Item Used to
Look in: Select the folder where the field file is to be selected from.
File name: Key in the name of the existing field file to be opened or to display a field file name selected from the Files list box.
Files of type: Select the type of files to be displayed in the file list.
Multiple Radiations to Same Point Select whether multiple observations to non fixed points are to be extracted.
Apply Curvature and Refraction Select whether earth curvature and refraction correction are to be applied during the extraction process.
The refraction (K) value and earth curvature used to calculate the correction are those currently set in the Utilities/Configure/Earth constants command. The formula used is also found in that topic.
Mean all Verticals Set whether all vertical circle observations observed as sets are to be used in calculating the averages.
Only sets of observations of field file record type 160 are used for this option.
If checked, then all vertical circle readings observed as sets will be used whether observed with a distance or not.
If the check box is not checked, then only vertical circle readings observed as sets and taken with a distance observation will be used. Leave the check box unchecked as a quality control measure to ensure that vertical circle readings used were all taken to the prism.
OK Extract the adjustment control observations from the selected field file into the currently open adjustment control file, and close the dialog box.
The OK button is only active after an adjustment control file has been selected.
The extracted data is displayed in the Least Squares Adjustment Editor.
Cancel Close the dialog box without extracting the control observations.

Any fixed co-ordinate points and their feature codes found in the field file are also extracted to the adjustment control file and displayed in the Least Squares Adjustment Editor 'Station' section.

The Point ID's and feature codes of observed points with unknown coordinates are also extracted to the adjustment control file and displayed in the Least Squares Adjustment Editor 'Station' section , awaiting the addition of approximate coordinates during the adjustment process.

The feature codes appearing in the 'Station' section with each point will be the first feature code for that point encountered in the field file, unless the point already exists in the SEE project. In that case the feature code of the SEE point is used. 

Directions extracted from the field file which were observed on datum (i.e. without a backsight point identifier and direction) are passed to the adjustment control file as bearings.

Distances extracted from the field file are reduced for slope to a horizontal distance which is passed to the adjustment control file. You have the option of applying mean sea level and line scale factor where appropriate as part of the adjustment process when the control file is adjusted using the Least Squares Adjustment Editor Compute menu. Refer to the Horizontal/Corrections command.

Height differences extracted directly from the field file are passed to the adjustment control file unchanged. However, height differences will also be computed if a control observation contains a slope and slope distance. These computed height differences can be corrected for earth curvature and refraction before being passed to the adjustment control file.