City of Ottawa 2005 Orthophotos
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The files were received in November 2006.

File Type:Tiff (.tfw)
File Size: 326GB for 737 tiles.
Resolution:20cm

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Compressed the original files using MrSID GeoExpress 6.1 from Lizardtech.

Compression Ratio: 20:1
Resolution: 20cm
Output File Type: MrSID Generation 3 files
Encoder version: 6.1.1.1513
Created ".sdw": Options/Preferences/General Tab - "Generate World File"

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MrSID Settings:
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-Used a "2-Pass Optimizer"

1-Pass or 2-Pass Optimizer

This option is only available for MrSID Generation 3 (MG3) images. The 1-pass and 2-pass optimizer parameters affect encode performance and memory usage. Although not as fast as the 1-pass optimizer, the 2-pass optimizer requires much less memory because it splits the encode operation into two passes. This is required on very large files.

Note that the “Estimated Memory Usage” value is only displayed (on the Job Properties panel and on the Advanced Settings tab of the Encode Options dialog box) when the 2-pass optimizer is used.

The 2-Pass optimizer is automatically used for Area of Interest encoding even if this checkbox has not been selected.

By default the 2-Pass Optimizer is used.

NOTE: Encoding with the 1-Pass Optimizer is faster but requires that the entire image be loaded into memory. If sufficient RAM is not available for the image selected, the encode job will fail.

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-Files were Optimized

Optimizable

The Optimizable parameter determines whether the output MG3 file can later be optimized. By default the optimizable checkbox is selected.

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-Made sure that "Create World File" was checked off to ensure that a ".sdw" was created.

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Made sure that World File Support: "Allow world files to override native georeferencing" was checked.  We did a test and checking this option retained the projection information of the tiff files.

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A city mosaic was created with the MrSID files which were, further compressed at a ratio of 100:1. The resulting mosaic was then compressed at 20:1.