= geometry =

 {X} '''''BACK UP YOUR WORK BEFORE RUNNING GEOMETRY!'''''

== Description ==
This program makes a surface by solving for the spacecraft position, spacecraft pointing, and landmark locations. This procedure iterates the solutions for camera pointing and landmark vectors sequentially.  

== Required Files ==
 * [[LMKFILES]]/
 * [[IMAGEFILES]]/
 * [[PICTLIST.TXT]]
 * [[LMRKLIST.TXT]]
 * [[LMRKLIST1.TXT]]
 * [[MAPFILES]]/
 * [[INIT_LITHOS.TXT]]    
 * [[SHAPE.TXT]] - This is the shape model that is stored in directory [[SHAPEFILES]]/.
 * [[SUMFILES]]/

== Output Files ==

 * [[SUMFILES]]/
 * [[LMKFILES]]/
 * [[MAPFILES]]/


== User Warning ==

 ''''' /!\ Always back up your work before using geometry.'''''

== Using geometry ==

The inputs for '''geometry''' are a list of operations where 
 * 1=landmark vectors, 2=camera pointing, 0=END
 * the number of iterations desired
 * a choice of whether to use limbs in determining camera pointing (y/n)
 * an option to do it all over again (y/n)

Here are two samples that show '''geometry''' inputs:

{{{
 GEOMETRY
 120<- do 1 followed by 2
 30 <- do them 30 times
 y  <- use limbs for pointing
 n  <- stop when done

 GEOMETRY
 20 <- do 2 only
 10 <- do it 10 times
 n  <- don't use limbs for pointing
 n  <- stop when done
}}}

The default is to do these operations for all landmarks in
[[LMRKLIST.TXT]] and all images in [[PICTLIST.TXT]].  

If [[INIT_LITHOS.TXT]]
contains a record

{{{
GEOPI='filename1'

or

GEOMAP='filename2'
}}}

then the files used are reduced. "filename1" is used instead of [[PICTLIST.TXT]] and "filename2" is used instead of [[LMRKLIST.TXT]].


== Input stdin ==

  . 1: landmark vectors. 
  . 2: camera pointing, scobj  
  . 0: end.  

 input operation list
{{{ 
   120
}}}

 enter number of iterations
{{{ 
   3
}}}

 use limbs for pointing? (y/n)
{{{ 
   y
}}}

 continue? (y/n)
{{{ 
   n
}}}


== PowerPoint Notes ==

=== Geometry Estimation Terms ===

 * '''Spacecraft State''' -  Position and orientation of spacecraft affects size and location of the body in an image. Errors are reflected by offsets of extracted image data from maplets for all maplets in the image.
 * '''Control Point Location''' -  An error in the body-fixed control point location is reflected by offsets of extracted image data for all images containing the maplets.
 * '''Rotation''' - An error in the transformation from inertial to body fixed frames is reflected in time-dependent offsets in extracted image data for all maplets in all images.
 * '''Differential Stereo''' - Errors in the maplet heights relative to the center are reflected by differential shifts of features within the extracted image data in addition to displacements from the maplets themselves.

{{attachment:geometry_imagedataoffset.jpg||width=400}}
{{attachment:geometry_errosfromincorrectdataoffset.jpg||width=450}}

=== More Detailed Description of Geometry ===

 * Global solution for camera pointing and body-fixed maplet location.
 * Iterative process:
  * Weighted least-squares solution of landmarks (control points) based on:
   * Nominal camera pointing and position
   * Relative landmark-to-landmark location
  * Weighted least-squares solution of camera position and pointing based on landmark location

{{attachment:geometry_outline.jpg||width=500}}

----------

''(Compiled by TC)''

CategoryPrograms