Camera Geometry
Introduction¶
In order to access and view the geometry for an ISIS image cube [raw instrument camera cube, (i.e., PDS-EDR)], the application spiceinit must be successfully applied to the cube. Once spiceinit has been applied, there are a number of applications that will be able to compute and output statistics about your image based on the raw Camera Geometry .
Camera Geometry¶
Camera Geometry refers to the viewing geometry of an observation. It also implies a 'non-projected' cube (sometimes referred to as a Level1, though it does not require radiometric calibration).
Within the ISIS environment, unless otherwise specified, ALL applications default (for input and output) to the following geometric reference (regardless of target body):
- Longitude Domain = 360 Longitudes will be reported in the range of 0 to 360 degrees (not -180 to 180)
- Latitude System = Ocentric Versus Ographic; Note: there is not difference for a spherical body
- Longitude Direction = East Longitude values increase to the east
Definitions for the geometric reference terms can be found in Learning About Map Projections
Camera Information Applications¶
Camstats¶
For a given image cube, the application camstats will report Minimum, Maximum, Average and Standard Deviation for the following:
Geometric Information
- Latitude
- Longitude
- Resolution, LineResolution, SampleResolution
- AspectRatio
Photometric Information
- Phase Angle
- Emission Angle
- Incidence Angle
- LocalSolarTime
- NorthAzimuth
Example (not all parameters shown):
camstats from=xxxx.cub linc=1 sinc=1
The linc and sinc parameters default to 1. For larger pixel size images, such as HiRISE or CTX data, setting the linc and sinc values to higher values (10, 100) would help the application to run faster. Set with care knowing that the application is literally skipping line/sample data to retrieve SPICE information.
- camstats supplies useful information that can be considered and applied when map projecting images (Level2 processing).
Mosrange¶
Given a list of multiple raw image cubes, the application mosrange computes the range of latitude/longitude and resolution statistics for all images given.
Example (not all parameters shown):
mosrange fromlist=list_of_lev0_w_spice.lis to=output_map_information.map projection=Equirectangular
-
This is one application that allows the user to specify output latitude type, longitude direction and longitude domain.
-
Knowing the information about your set of images at this point is useful, especially if the goal is to generate a mosaic. The output can be used later in defining the desired output map projection in Level 2 processing.
Campt¶
The application campt will supply geometric and photometric information based on a single latitude/longitude value (remember the raw camera geometry defaults when entering values) or a single line/sample coordinate of an image cube.
Geometric Information
- Latitude
- Longitude
- Resolution
Photometric Information
- Phase Angle
- Emission Angle
- Incidence Angle
In addition , this application will return a list of other spacecraft, sun and instrument related information such as:
- SpacecraftPosition
- SpacecraftAzimuth
- SubSpacecraftLongitude
- SubSolarLatitude
- SubSolarLongitude
- Time information (EphemerisTime, UTC)
Example (not all parameters shown):
campt from=xxxx.cub latitude=0.0 longitude=270.0 type=ground
or
Example (not all parameters shown):
Enter line/sample pixel location-current default of application
campt from=xxxx.cub line=512 sample=512 type=image
Phocube¶
phocube will compute and generate a separate output multi-band ISIS cube where each band will represent the selected (parameter=TRUE) geometric and photometric elements. The bands are named appropriately in the output cube labels: Group=BandBin .
Object = IsisCube
Object = Core
StartByte = 65537
Format = Tile
TileSamples = 128
TileLines = 128
Group = Dimensions
Samples = 1024
Lines = 1024
Bands = 6
End_Group
Group = Pixels
Type = Real
ByteOrder = Lsb
Base = 0.0
Multiplier = 1.0
End_Group
End_Object
Group = BandBin
Name = ("Phase Angle", "Emission Angle", "Incidence Angle", "Latitude", "Longitude")
End_Group
- phocube requires a successful spiceinit execution
- phocube can be applied to an unprojected "Level1" image cube or an individual map projected "Level2" image.
- phocube will not work on a mosaic cube, the photometric information for each input file is eliminated from the mosaic output file.
Example:
Run phocube on a fly-by Cassini ISS-Wide Angle Camera image of
Enceladus. In this example, phocube will generate a 6-band output
cube.
@TODO
The image used in this example has been processed through Level1 [ingestion, spiceinit and radiometric calibration]. Refer to: Working with Cassini ISS Data
Each band will contain the information asked for (parameters set to true) in the following command:
phocube from=W1487302209_2.lev1.cub to=W1487302209_2_pho.cub
phase=true emission=true incidence=true latitude=true longitude=true
- All bands of the phocube output can be displayed in qview
- To access a selected band in an application, use the cube-attribute syntax.
For example, calculate and report the average values of the Incidence
Angle (Band 3).
The command line for the stats applications is as follows:
stats from=W1487302209_2_pho.cub+3 to=W1487302209_2_inc_stats.pvl
The Example ISS Wide-Angle Camera image of Enceladus and the output of phocube :
