Geo-referenced raster files which do not use standard OS naming conventions

You may have raster files which are spatially referenced but do not correspond to any of the naming conventions understood by Cadcorp SIS Desktop 9.1.

There are two ways to handle these files:

1. Paste the raster image and then move it to its correct spatial location using Move Dataset.
   
2. Create an editable overlay (BDS file) and then paste the raster image to its correct positions (by means of gazetteering).
   When loaded, the BDS file then displays the raster data in its correct location.

How to create an editable overlay

1. Create or select a BDS on which to place the bitmap and ensure that its status is set to Editable. (If there are no editable datasets, Cadcorp SIS Desktop 9.1 creates a new untitled internal dataset where it places the bitmaps.)
   
2. Zoom to the correct location to paste the raster file.
   
3. Choose Home > Clipboard > Paste From.
   
4. In the File - Open dialog select the raster file.
   • In the case of BMP files, JPEG files, RLC files and TIFF there are two options: an ordinary file or a linked file. Use the linked option if possible.
   • The ordinary file option, Insert from Image copies the contents of the chosen raster file into the current overlay.
   • This copy then remains unchanged even if the original file on disk is edited or even deleted. However this can make your overlay very large and is therefore best used with small bitmaps (e.g a logo).
   • The linked file option has an identical effect visually but instead of copying the contents of the raster file, it creates a link to the chosen file.
   • If the computer requires memory currently taken up in displaying the raster image, a linked bitmap can be removed from memory to free up some space. This has the advantage of making far less demand on the computer’s memory resources, and allowing larger (in file size) bitmaps to be displayed.
   • Disadvantages of linked files are that they cannot be edited in Cadcorp SIS Desktop 9.1 (eg rubbersheeted), and if the file is deleted from disk, the image will also be removed from your map window.

5. Repeat steps 2 - 4 if you have several tiles which are to be joined together.
   
6. Save the BDS file using standard file naming conventions. This file can then be indexed if required.

Raster files which are not geo-referenced

A raster file which is not geo-referenced or does not use the standard naming conventions (e.g. SS7887nw), can either:

• be included in the Overlays dialog in the usual way. In this case it fills the current window, being located so that the centre of the bitmap is at the centre of the window.
  
• be placed in the correct spatial location as described as above.

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