Every map dataset displayed by the SDM comprises several layers. Every layer falls into one of the following categories:
Permanent Layers - defined and named in the Spatial Agent File (SAF) and may be of the following types:
- CARIS File Layer
- ESRI Shape Layer
- Raster (image) Layer
A particular map can have any number of permanent layers, but CARIS File Layers and ESRI Shape Layers cannot be in the same map.
Transient Layers - a fixed set of layers with the following names:
- "Transient Images"
- "Transient Polygons"
- "Transient Lines"
- "Transient Symbols"
- "Transient Names"
created dynamically, in the above order, by the SDM upon loading a map, to hold temporary features created by clients..
Special Layers - created dynamically by the SDM when special tags are detected in the SAF, as follows:
- "PyramidExtent" - created if the header section of the SAF contains the tag/value pair “IsPyramid:Y”
- "RITI polygons" - created if the SAF contains a CARIS File Layer of type “lines” which contains the tag/value pair “xferPoly:Y”.