FME considers a CADRG destination dataset to be a container folder name. Each feature type has a subfolder inside the container folder. Inside each subfolder, there is a table of contents file A.TOC and one or more subfolders containing some frame files. The frame files and their subfolders are named according to the specification MIL-STD-2411.
All raster features of the same CADRG feature type are grouped under one table of contents file. Each raster feature represents one boundary rectangle, but when the extents of the raster feature overlap two or more zones, the raster feature will be broken down into multiple boundary rectangles, each of which covers the raster subset in one zone. According to the specification, adjacent zones overlap each other, and the raster data in the intersection area will be repeated in the two boundary rectangles. Since each zone has a specific vertical/horizontal intervals and resolutions, the boundary rectangles may need to be resampled.
Each boundary rectangle will be broken down into one or more frame files. Each frame file has a size of 1536 x 1536. When the number of rows or columns in a frame is less than 4, the writer will not create the frame file, since the writer requires at least 4 rows and columns to do the spatial compression. The three palettes have 216, 32, and 16 entries, respectively when the raster does not have a NoData value, or 217, 33, and 17 entries, respectively, when the raster has a NoData value. Each palette entry is a four-byte value RGBM. The first byte R contains the red intensity level, the second byte G contains the green intensity level, the third byte B contains the blue intensity level and the fourth byte M contains a monochrome (grayscale) intensity level, which is an arithmetic combination of red, green and blue intensity levels. The equation used to calculate the monochrome intensity level is: 0.299 (Red) + 0.587 (Green) + 0.114 (Blue).
In the palettes, the last entries (the 217th, 33rd, and 17th entries, respectively) are reserved for the NoData value, or the “transparent” pixels, for cases where the data is missing or not available at the given geographic location. The RGBM values in the CADRG palette for the nodata entry are 0, 0, 0, 0.
For more information, please see Format Parameters and Feature Representation.
Workbench Writer Parameters
This format does not contain format-specific writer-level parameters.