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Camera Geometry


Introduction


In order to access and view the geometry for an ISIS3 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). It is IMPORTANT to note that within the ISIS3 environment, unless allowed to be 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

NOTE: 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):
Enter lat-Ocentric/long-360 point location

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 ISIS3 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.

  • NOTE: 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:

Cassini ISS WA-camera Enceladus Iss_WAC_ema_figure.png Iss_WAC_inc_figure.png

Iss_WAC_phase_figure.png Iss_WAC_lat_figure.png Iss_WAC_lon_figure.png

Iss_WAC_enceladus_sm2.png View (39.4 KB) Kristin Berry, 2016-05-31 12:57 PM

Iss_WAC_ema_figure.png View (63.6 KB) Kristin Berry, 2016-05-31 01:17 PM

Iss_WAC_inc_figure.png View (61.2 KB) Kristin Berry, 2016-05-31 01:17 PM

Iss_WAC_phase_figure.png View (30.9 KB) Kristin Berry, 2016-05-31 01:17 PM

Iss_WAC_lat_figure.png View (33.6 KB) Kristin Berry, 2016-05-31 01:17 PM

Iss_WAC_lon_figure.png View (43.2 KB) Kristin Berry, 2016-05-31 01:17 PM