= Find normal =

([[lithos]] '''Main Menu Option N. Find normal''')

== Description ==

This Main Menu option calculates the normal vector to the maplet in one of several ways.

=== Suboptions ===
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.

== Typical Example ==
The following sample shows the command input for the most common suboption choice, '2':
{{{
n
2
}}}


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(Compiled by JRW)

CategoryLithosMenu