The GM_ContourParams_t type exposes the following members.
Bounds of contour lines to create. Pass empty rectangle to use entirety of passed in layer(s).
ADVANCED: Create contours as we from above to contour rather than from contour to below.
Do not smooth the generated contour lines to improve their appearance
Generate iso-height areas in addition to contour lines
Generate spot elevation points at minimum and maximum elevations
Set to TRUE if the contour interval is in feet rather than meters
Only include the value (and not the units string) in the contour labels
Display contour generation progress dialog
Only create a single contour level rather than treating as interval