Turn on extract filter
(lithos Main Menu Option X. Turn on extract filter)
This Main Menu option turns on shadow masking.
Use this almost always since you do not want shadows to be interpreted as topography.
The extract filter:
enhances shadows by extending them into the lit portion. This is done because shadows are not sharp, particularly if the image is lower in resolution than the maplet, and this is interpreted as topography by the lithos software.
zeroes out data in regions that, according to the current maplet topography, should not be seen in an image. In many cases the maplet is seen obliqely in the image and some areas, especially the bottoms of craters, cannot be seen. This action is accomplished by using both a restriction on emission angle and ray tracing.
zeroes out data in regions that, according to the current maplet topography, should not be in shadow. It does this through ray tracing.
When you choose Option X. Turn on extract filter from the Main Menu, you will see this prompt:
Main Menu: Q 0123O IUCRSG NVAMBX DEPL FZH? x >x enter tolerance .025 Current landmark = EE0001 SCALE = 0.000100 QSZ = 49 Lat/Lon/Rad = -6.806 264.097 0.266 Region = EE gc LMRK_DISPLAY0.pgm gc LMRK_DISPLAY1.pgm check display Main Menu: Q 0123O IUCRSG NVAMBX DEPL FZH?
enter tolerance - Enter '.025' (the standard input).
(Compiled by JRW)