NOTE: This section was formerly referred to as “Updating MrSID Mosaics.” The command line parameters have been simplified so that they are an extension of the command used to create a flat mosaic.
GeoExpress provides the ability to create an MG3 or MG4 image composed of other images. Such an image is called a composite mosaic. (For more about the difference between flat mosaics and composites, see Creating a Mosaic.)
An MG4 composite can only include MG4 images, but tiles can be different resolutions.
An MG3 composite can include MG3 and MG2 images, but all tiles must be the same resolution.
All images included in a composite mosaic must have the same color depth and be in the same colorspace.
Note that any included MG3 or MG4 image can itself be a composite mosaic; in this way you can add to or update an existing mosaic.
In order to create a composite mosaic, use the following syntax:
mrsidgeoencoder -i tiles.mos -o outputcomposite.sid -composite
The mosaic file (tiles.mos in the example) lists the images to be used to create the composite mosaic.
The command line switch -composite indicates that the output file should be a composite mosaic, not a flat mosaic.
In the following example, an image is created from four MrSID files.
A sample mosaic file (fourcorners.mos) for this project is displayed below:
image_nw.sid
image_ne.sid
image_sw.sid
image_se.sid
The following command creates the image using the mosaic file above:
mrsidgeoencoder -i fourcorners.mos -o compositemosaic.sid -composite
NOTE: GeoExpress does not recognize mosaic files with spaces in either the listed file names or in the listed paths. In addition, the first line in the file cannot be blank and the last line in the file must be followed by a carriage return.
You can generate a shapefile that identifies the boundaries of each tile that makes up the mosaic. Include the switch -writeboundsshapefile (or -wbshp) in your command:
mrsidgeoencoder -i fourcorners.mos -mos -o compositemosaic.sid -composite -writeboundsshapefile
Your job will be created and include the file compositemosaic.shp (or whatever name you chose for your output file). You can then use a program such as GeoViewer to load the image and shapefile to see the tile boundaries overlaid on the output file.