This file contains the Orthoimagery of the City of London and should only be used once you have read and agree to the licence information found in the “ReadME – Ortho Licence 2011.htm” file. The original 'SID' Generation 3 (MG3) file, at a 15cm pixel resolution, was recompressed at a 50:1 compression ratio.


Notes:        The data is not suitable for accurate measuring and/or scaling, but if necessary the distances will be 'grid' not 'ground' values.


Coordinate system: UTM - NAD'83, 6° projection, Zone 17.

Central Meridian 81° West.

Aerial photography scale: approximately 1:15400.

Aerial photography date: April 2011.

Ground pixel resolution: 15cm.

The file size is approximately 2.0GB.

Source format: 'SID' World.

'SID' created: August 2011.





This file contains the associated geographic positioning file (world file). It includes the Image units per pixel in a real world measurement and the real world X, Y coordinates of the upper left corner of the dataset.


Notes:        The “London50_RGB 2011.sid” and the “London50_RGB 2011.sdw” files must reside in the same directory for the program to read the image extents and pixel information to retain the UTM - NAD'83 coordinate settings.


The file size is approximately 0.001mb.

'SDW' created: August 2011.


Viewing the compressed 'MrSID®' file will require a Plug-in or a Viewer. One is presently available free-of-charge from LIZARDTECH, Inc., as of the date of this publication. May have limited commercial use, please read the terms.


The following instructions will assist you in downloading the appropriate program:

1) Visit the LizardTech website located @

2) Click on the 'DOWNLOADS' link on the tab located along the top of the page and you will be taken to a product or category list of available downloads.

3) Select the desired ‘Viewer’ and/or ‘Plug-in’ for the program(s) of your choice. The most popular for Netscape® or the Internet Explorer Web Browser is the “ExpressView Browser Plug-in” (MrSID®).

4) Click on the ‘WINDOWS’ link for the selected download and you will be taken to a product information page.

5) Click on the ExpressView Browser Plug-in for Windows ‘Download’ link and you will be taken to the download page to continue either automatically or manually.

6) The software can be installed using the automatic ‘Web Install’ or download it and run the self extracting installer at a later date.