Editing Control or Calibration Points

Calibration Editing:
You can display and edit all the calibration values in a table.  The editing table is loaded from the image by default, but you can also load from a disk file in one of several formats and save them as well.  

If the chosen grid is from the EPSG Database

then you can see the EPSG number.

If UTM has been chosen, then you can see the UTM zone number.

Modifying an extant single point:

When in either control point or calibration point entry mode, hold down a Shift button on the keyboard, carefully centre the control or calibration cursor or magnifier over a point and left click.  This will bring up the dialogue box used at entry, and you can change various parameters. 

Using known coordinates:

Sometimes there are reasons for wanting to enter a control point at known geographic grid coordinates in a calibrated image. One example might be from data obtained with distance measuring equipment (DME) for points which are not visible on a map, but which are visible in an air photo. Another reason might be for entering known points just outside the visible area of the map. For a single control point when in control point entry mode, press F6, but there are some circumstances where you may want to import a whole set of coordinates from an external file made by some kind of DME device. Frequently, such sets of coordinates may contain heights as well. Go to the control point menu and select Edit.

This will show any control information you may have. 

You may modify any of the items in the editing box and then save the result to the extant image to test the effect of what you have done. If you are dissatisfied, return to Edit and try again. If you are sure that all is well, you may save directly to the control point file or to an asci file as well.

You may modify any field either by double clicking on it and entering new values or checking or unchecking disabling, or you may use the menu Modify/F2 option if you prefer after moving to a field with the arrow keys. Control and calibration points may also be inserted or deleted, but you are responsible for using identity numbers which are not already in use.

You may also edit calibration points. Please note that the identification numbers for these always begin with the number 9 and must never have more than 4 digits, so that the maximum number of calibration points is 999. Control points are numbered from 0001 to 9999. Both for calibration and control points, you may add or change height values if you wish. You may also alter the pixel coordinates or the grid coordinates of any of these points. 

For new data from other sources open the file menu and choose an asci file with your x, y and optional z coordinate data. The program accepts files in text format only, with carriage return and line feed at the end of each line (Windows Notepad format, for example) and any one of the following 5 delimiters used to separate data on each line:

tab or comma (,) or  dollar($) or forward slash(/) or blank( )

You must use only one delimiter between items, but any number of blanks are permitted for formatting purposes if you do not use one of the other delimiters.

Each line of data represents at an x and y coordinate pair, for example:

1)  x, y


2)  x, y, z , where z is a height value in the same reference system used for x and y.

3)  id, x, y,  where id is the identity number 

4)  id, x, y, z

5)  id, xpixel, ypixel, x, y, where xpixel and ypixel are the pixel coordinates of the point in the image

6)  id, xpixel, ypixel, x, y, z

7)  id, xpixel, ypixel, x, y, z, zone, where zone is a UTM zone number

8)  id, xpixel, ypixel, epsgcode,  x, y, z, zone, where epsgcode is a valid number from the EPSG database list

9)  id, xpixel, ypixel, epsgcode,  x, y, z, zone, enabled, where enabled is either 0 or 1,  1 representing an enabled calibration point.

You can edit any of the points by clicking on a point and typing or pressing F2 when the blue background is present or using the Modify option on the Edit menu. You can also insert a new blank line for entering more values or delete an existing line either with the Ins and Del numeric keys or with the Insert or Delete options on the Edit menu:

When you have finished, you may press Save to Image on the File menu to save the values to the normal calibration or control  point storage trees. You can also enter new values which have not been loaded from an external Asci file, but see the note below before doing so.

You can also Load from image, the values from previously existing control points to examine and edit them if you wish. You may Save to image  to replace any added or edited points to the image control point data structure. Please note that this will not be saved to a .ctl file if you close the image using the emergency exit door toolbit, or use Alt-F4 or the upper left corner tab. You can save to a new set of control points and to the image simultaneously if you use SaveAs (new control). In that case you will be prompted for a new file name to which the data can be saved in binary control point form. You may also Export Asci a loaded or imported control point set to a new asci file. Finally, you may Import + Append to import multiple sets of asci control files and add them to any of the data already in the table.


The active field in the table has a blue background. When you switch to edit mode either by pressing F2 or choosing Modify  from the Edit menu or by starting to type in the field, its background changes to grey. The editing only becomes effective when you leave the field either by clicking on another with the mouse, or using any of the keypad movement commands. If you close the table before doing so, the change you have made will not be recorded.

When editing a numeric field:

Double click on the field or press F2 to change the active (blue background) field to edit mode (grey background). Type in new values as required. Move back and forth in the field with the arrow keys on the numeric keypad. 

<CtrlY>Erase the field's content.
<CtrlZ>Restore the field's original content.
<Bksp>Erases one character to left of cursor in value.

Navigation in the Edit dialogue box:

With the numeric keypad:

<Home>Move the active cell to the first column.
<Left>Move the active cell left to the previous cell.
<Right>Move the active cell right to the next cell.
<Down>Move the focus to the next row.
<Up>Move the active cell up to the previous row.
<End>Move the focus to the last column.
<PgDn>Move the active cell to the page following the current page.
<PgUp>Move the active cell to the previous page.
<CtrIHome>Move the focus to the first cell in the table.
<CtrIEnd>Move the active cell to the last cell in the table.
<CtrlUp>Move the active cell to the top left cell.
<CtrlDown>Move the focus to the cell at the bottom right of the table.
<CtrlPgUp>Move the active cell to the top of the page.
<CtrlPgDn>Move the active cell to the bottom of the page.
<F2>Enter exit table edit mode (or just start typing in the active cell)

With the Mouse:

Drag on the scroll bar to bring a row into the visible area if there are more rows than can fit in the dialogue box. Click on any cell to activate it and make it ready for editing. Click on any other cell to confirm the edit.


The program makes no checks on the validity of the data you have either imported or entered by hand. It rejects duplicate id numbers and duplicate coordinate values. If you import with four or more fields present, you must administer your id numbers carefully. Zero is not permitted as an id number. You must enter an id number in every row, or the row will not be exported or loaded.

You are strongly advised not to use this method for entering raw control information.