(lithos Main Menu Option N. Find normal)
This Main Menu option calculates the normal vector to the maplet in one of several ways.
When you choose Option N. Find normal from the Main Menu, you will see this set of Suboptions:
Main Menu: Q 0123O IUCRSG NVAMBX DEPL FZH? n >n 1. Normal from radius vector 2. Normal from heights 3. Normal from shape 4. Normal from stereo q. Quit
1. Normal from radius vector - Sets normal the same as the radius vector. (Rarely used.)
Note that the normal is the same as the radius vector everywhere if the object is a sphere. Rarely will conditions on an asteroid be such that this option will be correct.
2. Normal from heights - Determines normal from the average of the heights in the maplet by fitting a plane to the current topography. (Used almost exclusively.)
3. Normal from shape - Determines normal from the shape model.
4. Normal from stereo - Determines normal from three common points in two images.
This option is occasionally used when the shape is extremely challenging and no good model yet exists. It requires manual determination of common points.
The following sample shows the command input for the most common suboption choice, '2':
(Compiled by JRW)