The size of a mosaic is calculated from the nominal size of the output mosaic. For raster images, the nominal size is the product of the image width, the image height, the number of bands, and the number of bytes per band. Also for raster images, the nominal size assumes that all portions of the image include valid data, whether or not this is the case. For LiDAR point clouds, the nominal size is a measure of the number of points in the point cloud and the number of fields for each point.
As a result, the size is not adjusted for the presence of transparency regions in the mosaic, such as when:
In these cases, the transparency regions in the output image are included in the mosaic size. Also in these cases, the estimated output file size may be considerably larger than the actual output file size.
NOTE: The cost charged to the data cartridge is not always equal to the mosaic size. It is calculated from the sum of the nominal sizes of the input tiles rather than from the nominal size of the resulting mosaic.