GeoExpress - Knowledge Base Articles

A060305 - Cannot add a no-data value when mosaicking existing MrSID images

Products:

GeoExpress

Summary:

Cannot add a no-data value when mosaicking existing MrSID images. In creating a composite mosaic of MrSID images, you cannot select a no-data value for transparency.

Cause:

This behavior occurs because in the creation of a composite mosaic the existing tiles are simply written to new files. The nodata for composites is defined in the source MrSID tiles (whether pixel value or — in MG4 — an alpha channel) so this option is not settable.

Solution:

In order to specify a new no-data value when creating a mosaic of MrSID images, you must create a flat mosaic rather than a composite. This option is selected in the dialog that appears when you click the Create New Mosaic button.

Creating a flattened mosaic completely re-encodes the images. This will result in slightly longer encoding times.

Mosaicking existing MrSID images, whether composite or flattened, does not charge against your data cartridge.

Status:

This is by-design and not expected to change.

Reference Number:

TT-8994

This article was last updated or verified on 18 October 2012.