(This functionality is available with the Transformations
module)
The Transformation Editor is displayed after selecting the Define Transformation command from the transformations task. This editor may be used to define a transformation.
The colours used in the Transformations Editor are set using the Utilities/Configure/Colours/Table command.
Each row in the editor consists of a pair of points, one a control point and the other a local point. The aim is to compute projection parameters that give a best fit mapping of the local points onto the control points. For any pair of points, the local point and the control point are deemed to be physically the same point but on different co-ordinate systems.
| Item | Used to |
| Control: | Enter the control points and co-ordinates which represent the co-ordinate system that you will transform to. |
| Local: | Enter the control points and co-ordinates which represent the co-ordinate system that you will transform from. |
| Cells: | Display the data in the currently open transformation file and to
select the active cell enabling its value to be edited. The currently active cell is highlighted with a border. The currently active cell is selected by clicking the required cell with the mouse or by using the arrow or Tab keys to move the border to the required cell. If the required point is in the currently open data base, simply select it with the mouse and the cells for that point are automatically filled in. |
| Pt Id Column: | Display or edit the point identifiers. |
| East: | Display or edit the east co-ordinates. |
| North: | Display or edit the north co-ordinates. |
| Code: | Display or edit the feature codes. |
| Description: | Display or edit the descriptions. |
| Weight: | Display or edit the weights to be used in the transformation for
each pair of points. Note that if the weight column is on in the editor, a weight must be entered for each pair of points before the projection can be computed. If the weight column is off, then a weight of 1 is automatically used for each pair of points. |
Tool Bar The following special tools are available in the Control File Editor.
The tools run the following commands (in order from left to right).
| Item | Used to |
| File/New: | Create a new untitled transformation file. |
| File/Open: | Open an existing transformation file. |
| File/Save: | Save the current transformation file to disk. |
| File/Save As: | Save the current transformation file to disk. |
| File/Cut: | Cut a selection of rows to the clipboard. |
| File/Copy: | Copy a selection of rows to the clipboard. |
| File/Paste: | Paste the clipboard contents into the selected rows. |
| File/Retrieve Co-ordinates: | Extract co-ordinates from the currently open data base for the points
selected in the editor. The point ID's selected in the editor must exist in the data base for this operation to be performed. |
| Edit/Match Point ID's: | Create a corresponding local or control point (to make up a pair),
with the same point identifier as that selected but using the co-ordinates
of that point identifier from the currently open database. The point ID's selected in the editor must exist in the data base for this operation to be performed. |
| Edit/Exclude: | Exclude or include the selected point pair in the transformation definition. Excluded pairs are shown in italic. |
Note:
Once the point data is entered via the mouse or using 'Match Point ID', they will not be changed if the corresponding points in the current database are subsequently modified.