Calibrating GeoPortal Variants

Unfortunately there are no standards for the scripts which run a GeoPortal Web site.  Each one is different.  Therefore a minimal set of tools has been incorporated into AirPhotoSE which permits extracting basic image and geographic information from most sites for further processing in AirPhotoSE.  These use the Windows Clipboard to exchange data between the site and AirPhotoSE.

All appropriate parameters must be set using the GeoPortal itself. AirPhotoSE can not do this directly, since the scripting code of the site is not standardised and is sometimes encrypted.  The available parameters often include a choice of grid system, a scale and the theme to be shown, e.g. an orthophoto, a map,  names and other features. Undesired features which should not be visible in output images must be disabled by using the options offered by the geoportal.

The keyboard operations used for interchanging values between data entry fields of a GeoPortal site and the coordinate fields on the upper toolbar of  AirPhotoSE include:

In the GeoPortal user-modifiable data fields:

Shift/Home  Highlight the content of a field after entering data.
Shift/End  Highlight the content of a field if the cursor is at the left edge of the field.
Ctrl_C  Copy the highlighted content of a field to the Clipboard.
Del  Delete the content of a highlighted field.
Ctrl_V  Transfer the content of the Clipboard to a field.

AirPhotoSE monitors the Clipboard continuously for any change made in the GeoPortal followed by Ctrl_C and places a coordinate value saved to the Clipboard with Ctrl_C in the upper toolbar field or fields. 

Alt + M to set a screen marker at the cursor's position. If coordinates have been written to or copied from the Clipboard to the East and North fields of the main capture window, they will be written next to the marker as well as in the GeoPortalFiles.txt protocol file when the programme closes.

In AirPhotoSE:

Tab    Copy a modified value in one of the coordinate fields of AirPhoto SE to the Clipboard from which it can be entered into the appropriate GeoPortal field using Ctrl_V in that field. 

Alt + S to Copy the full GeoPortal screen to an overlying layer belonging to AirPhotoSE and display a selection rectangle which may be dragged  to and stretched to include an area of interest and exclude items which should not appear in the result. The colours of the selected area are inverted for better visibility.

If a background map shows a grid, this makes placement and transfer of values for a marker much easier. If coordinates are shown by the site as the mouse is moved, pressing Alt+S to capture the image leaves the coordinates unchanged, and these can be typed into the East and North fields, or copied to the Clipboard if they are showing in the search fields of the site. 

Shift/Right click  Opens a file name dialogue box to permit entering a name for a file to contain the first area captured.

Right click  Capture additional areas after moving the underlying GeoPortal image and pressing Alt-S again or clicking on the Save and Capture menu item.

The first image file in a selection sequence should be given a short name.  Sequence numbers will be entered automatically by the programme after the short name and the file name extension. Three digit automatic sequence numbers are generated.  Image files are not overwritten if a file name is generated in a subsequent programme session.  If image files have been deleted, a new name is generated with the first available sequence number which is free.  If the Shift button was not held down for the first capture, then only the sequence numbers will be used for the file names.

Further screen captures, after changing the position of the image on the screen with the tools offered by the Geoportal, may be sequentially numbered using the initially chosen file name as a prefix simply by pressing Alt-S again followed by Right-Click with the mouse.

Many GeoPortal sites offer a search option using coordinates in one or more map grid to zoom to a point of interest.  Some require entering East and North parameters in separate fields:

The content of a field can usually be edited in the GeoPortal. The value can be highlighted by holding down and dragging the mouse over it and releasing it or by using the Shift and the arrow keys or with the Shift-Home keyboard combination.  Follow this with Ctrl-C to copy the data to the Clipboard.  When two fields must be used, then the operation must be repeated on each field separately.  Always start with the East / X field first and then copy the North / Y field. 

Some GeoPortal sites permit entering the search coordinate pair in a single data entry field:

After highlighting the search values in the GeoPortal search field or fields and pressing Ctrl-C on the keyboard, the search values are also transferred and displayed on the uppermost toolbar of the AirPhotoSE GeoPortal page and the programme remembers that the data was entered from a single field and separates the East and North values for the toolbar fields appropriately.

To change the search position by a known amount in 500 meter increments without having to do mental arithmetic, click on the upper toolbar to change the focus from the GeoPortal search fields and then click on the spinners for the East and North fields there. 

Then press the Tab key to transfer the changed value or values to the Clipboard.

Finally, return to the search fields in the GeoPortal, clear the value or values and press Ctrl-V to transfer the new values from the upper toolbar to the GeoPortal field and then press the search button of the GeoPortal site to move the image to the new position.

If the GeoPortal site supports search using the UTM-WGS84 grid and you have selected that grid in the Options dialogue, a UTM zone field with an attached spinner will also be displayed on the upper toolbar.  Set the value for the area of interest using the spinner.

From the File menu on the GeoPortal page you may choose the Edit option to examine the values which have been entered automatically in a list of images and coordinates

If a value appears to be incorrect, you can remove it from the list by highlighting the row and pressing Delete followed by Exit to close the editing window.  

If you have installed the Microsoft ICE image compositing editor, you can click on the Run ICE entry to see how the separate image tiles align

When using ICE with a large number of tiles, it may be necessary to set the Stitch option manually to one of the three Planar Motion choices to prevent ICE from warping the output when you click it's Export to disk button.  If, instead of orthophotos, you have chosen black and white or greyscale maps in the GeoPortal, make certain to choose the Export format as Windows Bitmap and not JPEG, or the map lines will be fuzzy after transformation in AirPhotoSE.  

Click on the Automatic Crop button in ICE before Exporting and scroll the result with the mouse to make sure that all of your area of interest is included.  If not, return to the GeoPortal and select and capture any missing areas following the instructions above.  If ICE has excluded some images because they don't overlap adjacent images sufficiently for stitching, add images in the missing areas.  These can simply be moved using the image shifting options of the GeoPortal.  If that is used, set the coordinate values in the upper toolbar fields to zero so that previous values will not be recorded in the image list data in the wrong rows.  If not otherwise chosen, ICE uses the name of the last image tile incorporated into the composite picture with the addition of "_stitch" unless you choose the output name.

When you are satisfied with the results, choose the Save option from the GeoPortal menu and write the list of image and coordinate data as a text file. This may be reloaded with the Load option if you have to interrupt your work.  The data is also recorded and saved to the default GeoPortal list text file.  

Now you can proceed to calibrate your result in AirPhotoSE normally while displaying the saved list text file from which you can transfer coordinate values into the calibration dialogue using copy and paste with the Clipboard.  This will avoid numerical typing errors. A result from a site which automatically writes coordinates as well as a marker looks like:

Although many GeoPortal sites place markers at the centre of an image found using their search option, few do so in the same way and the markers are all different.  If the site permits you to enter numerical text data near or at a marker automatically, that is very useful.  It is not advisable to enter this data manually, since numerical typing errors are easily made, but you may copy and paste the numbers from the fields in the GeoPortal Edit window into the text entry fields of the GeoPortal to avoid errors.

If you have chosen one of the GIS options in the Options dialogue, a georeferenced file for the chosen GIS will be written as well.