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ISIS Application Documentation


photrim

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Trims pixels outside of phase, incidence, and emission angles

Overview Parameters Example 1 Example 2

Description

The photrim program trims pixels outside of the phase, incidence, and emission angles by setting them to "null" within all bands of the cube. A user can either trim using the program's default method or the USEDEM method.

By default, photrim uses the angles calculated from the ellipsoidal surface to trim an image. The ellipsoid is retrieved from the IAU/NAIF target body file, which is defined within the cube's kernel group as the TargetAttitudeShape. If the USEDEM option is selected, then photrim will use the angles calculated from the digital elevation model (DEM) to perform the trim instead. The DEM is referenced in the ShapeModel keyword within the input cube's kernel group. Note that photrim does not trim using local slopes.

Angle Definitions:

Phase Angle - The angle between the sun vector to a point on the ellipsoid and the instrument vector to the same point.
Incidence Angle - The angle between the sun vector to a point on the ellipsoid and the normal at that point.
Emission Angle - The angle between the instrument vector to a point on the ellipsoid and the normal at that point.

Examples of special cases:

1) If the instrument is directly between the point and the sun, then the phase angle is 0; if both the sun and the instrument are both along the normal to the point, then the phase, incidence and emission angles are all zero.

2) If the instrument is looking along the normal and the sun is illuminating the point, then the emission angle is 0 and the incidence and phase angles will be in the range of 0 to 90 and equal to each other.

3) A point on the surface of an ellipsoidal body cannot be illuminated if the incidence angle is greater than 90 degrees.

4) A point on the surface of an ellipsoidal body cannot be visible if the emission angle is greater than 90 degrees.

5) If a point is both illuminated and visible, then the phase angle ranges from 0 to less than 180.

Categories


Related Applications to Previous Versions of ISIS

This program replaces the following application existing in previous versions of ISIS:
  • trimangle

History

Tammy Becker1999-02-11 Original version
Stuart Sides2003-06-04 Converted trimandle to Isis 3.0, and made it trim only on phase, incidence and emission angles.
Stuart Sides2003-07-29 Modified filename parameters to be cube parameters where necessary
Steven Lambright2008-05-13 Removed references to CubeInfo
Marjorie Hahn2016-08-05 Added the option to use the digital elevation model when trimming the image. Created examples for using the DEM and not using the DEM. Fixes #4181. Converted to callable app and converted Makefile tests to gtests.

Parameter Groups

Files

Name Description
FROM Input cube to trim
TO Output cube

Digital Elevation Model

Name Description
USEDEM Specify if DEM photometric angles will be used to trim image

Photometry

Name Description
MINPHASEMinimum phase angle to trim
MAXPHASEMaximum phase angle to trim
MINEMISSIONMinimum emission angle to trim
MAXEMISSIONMaximum emission angle to trim
MININCIDENCEMinimum incidence angle to trim
MAXINCIDENCEMaximum incidence angle to trim
X

Files: FROM


Description

Use this parameter to select the filename. All bands within the file will be trimmed.

Type cube
File Mode input
Filter *.cub
Close Window
X

Files: TO


Description

This file will contain the results of the trim.

Type cube
File Mode output
Close Window
X

Digital Elevation Model: USEDEM


Description

This specifies if the image will be trimmed based on the photometric angles obtained from the DEM surface or the ellipsoid. If this parameter is set to false, then the photometric angles will be obtained from the ellipsoidal surface.

Type boolean
Default FALSE
Close Window
X

Photometry: MINPHASE


Description

Pixels which have a phase angle less than this value will be trimmed.

Type double
Default 0.0
Minimum 0.0 (inclusive)
Maximum 180.0 (inclusive)
Less Than or Equal MAXPHASE
Close Window
X

Photometry: MAXPHASE


Description

Pixels which have a phase angle greater than this value will be trimmed.

Type double
Default 180.0
Minimum 0.0 (inclusive)
Maximum 180.0 (inclusive)
Greater Than or Equal MINPHASE
Close Window
X

Photometry: MINEMISSION


Description

Pixels which have an emission angle less than this value will be trimmed.

Type double
Default 0.0
Minimum 0.0 (inclusive)
Maximum 90.0 (inclusive)
Less Than or Equal MAXEMISSION
Close Window
X

Photometry: MAXEMISSION


Description

Pixels which have an emission angle greater than this value will be trimmed.

Type double
Default 90.0
Minimum 0.0 (inclusive)
Maximum 90.0 (inclusive)
Greater Than or Equal MINEMISSION
Close Window
X

Photometry: MININCIDENCE


Description

Pixels which have an incidence angle less than this value will be trimmed.

Type double
Default 0.0
Minimum 0.0 (inclusive)
Maximum 180.0 (inclusive)
Less Than or Equal MAXINCIDENCE
Close Window
X

Photometry: MAXINCIDENCE


Description

Pixels which have an incidence angle greater than this value will be trimmed.

Type double
Default 90.0
Minimum 0.0 (inclusive)
Maximum 180.0 (inclusive)
Greater Than or Equal MININCIDENCE
Close Window

Example 1

Trimming an ISIS cube using the ellipsoid model

Description

This is an example of trimming an ISIS cube without accounting for the DEM. Instead, the program will trim the cube based on the ellipsoid.

Command Line

photrim FROM=AS15-M-1499_msk-L2_1250mpp.cub TO=photrim_no_dem MAXEMISSION=88
Run photrim with a max emission value of 88.

GUI Screenshot

Example Gui

Example GUI

Screenshot of the photrim GUI with a max emission angle of 88. The reset of the parameters are set to the program defaults.

Input Image

Input Cube

Input Cube

Parameter Name: FROM

The untrimmed cube. This is an oblique view of the moon acquired by the Apollo Metric camera.

Output Image

Output Cube

Output Cube

Parameter Name: TO

The result of trimming the cube using the ellipsoid model and a max emission angle of 88.


Example 2

Trimming an ISIS cube using the digital elevation model.

Description

This example shows the result of trimming an ISIS cube while accounting for the digital elevation model of the cube.

Command Line

photrim FROM=AS15-M-1499_msk-L2_1250mpp.cub TO=photrim_dem USEDEM=TRUE MAXEMISSION=88
Run photrim using the digital elevation model and a max emission value of 88.

GUI Screenshot

Example Gui

Example Gui

Screenshot of the photrim GUI with a max emission angle of 88 degrees and with the option to use the digital elevation model selected. The rest of the parameters are set to the defaults.

Input Image

Input Cube

Input Cube

Parameter Name: FROM

The untrimmed cube. This is an oblique view of the moon acquired by the Apollo Metric camera.

Output Image

Output Cube

Output Cube

Parameter Name: TO

The result of trimming the input cube using the DEM and a max emission angle of 88 degrees.