photrim
Trims pixels outside of phase, incidence, and emission angles
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.
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 Becker | 1999-02-11 | Original version |
| Stuart Sides | 2003-06-04 | Converted trimandle to Isis 3.0, and made it trim only on phase, incidence and emission angles. |
| Stuart Sides | 2003-07-29 | Modified filename parameters to be cube parameters where necessary |
| Steven Lambright | 2008-05-13 | Removed references to CubeInfo |
| Marjorie Hahn | 2016-08-05 | 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. |
Parameters
Files
Use this parameter to select the filename. All bands within the file
will be trimmed.
| Type | cube |
|---|---|
| File Mode | input |
| Filter | *.cub |
This file will contain the results of the trim.
| Type | cube |
|---|---|
| File Mode | output |
Digital Elevation Model
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 |
Photometry
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 |
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 |
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 |
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 |
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 |
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 |
Example 1
Trimming an ISIS cube using the ellipsoid model
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
Run photrim with a max emission value of 88.
photrim
FROM=AS15-M-1499_msk-L2_1250mpp.cub TO=photrim_no_dem MAXEMISSION=88
GUI Screenshot
Example GUI
Example GuiScreenshot 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.
This example shows the result of trimming an ISIS cube while accounting for
the digital elevation model of the cube.
Command Line
Run photrim using the digital elevation model and a max emission value of 88.
photrim
FROM=AS15-M-1499_msk-L2_1250mpp.cub TO=photrim_dem USEDEM=TRUE MAXEMISSION=88
GUI Screenshot
Example Gui
Example GuiScreenshot 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.