skymap

This program converts a cube in camera coordinates to a map projection. It differs from the application "cam2map" in that it maps camera ra/dec (right acsension/declination) to map projection longitude/latitude. The program is useful for inflight geometric and optical distortion calibration of a camera when star images are collected. The input cube labels must have an Instrument Group and Kernels Group. That is, the program "spiceinit" should be run on the input cube prior to "skymap".

This program will pick appropriate defaults for most parameters. In particular for the MAP parameter, it will generate the following:

  Group = Mapping
    TargetName             = "Sky"
    EquatorialRadius       = 1.0
    PolarRadius            = 1.0

    LatitudeType           = Planetocentric
    LongitudeDirection     = PositiveEast
    LongitudeDomain        = 360

    MinimumLatitude        = Computed from the input camera cube or map file
    MaximumLatitude        = Computed from the input camera cube or map file
    MinimumLongitude       = Computed from the input camera cube or map file
    MaximumLongitude       = Computed from the input camera cube or map file

    ProjectionName         = Projection name in the map file
    Scale                 = Computed from the input camera cube or map file
  EndGroup
    

Note that although the map projection group reflects latitude/longitude, those values are synomous with declination/right ascension.

Note that an important concept here is a Mapping group can come from any PVL file. You can use an existing map projected cube as input for the MAP user parameter. Because the cube has PVL labels and contains the Mapping group, you will essentially force the input camera cube to have the same mapping parameters or match the existing cube. Information about map projections and the Mapping group can be found in the Isis user documentation.

Finally, the user has the option to override the pixel resolution and the ground range (latitude/longitude). These changes can be facilitied through the parameters SCALE, SRA, ERA, SDEC, and EDEC.

Description

The specification of the input cube to be projected. The cube must contain a valid Instrument and Kernel group in the labels.

Type	cube
File Mode	input
Filter	*.cub

Description

A file containing the desired output mapping parameters in PVL form. This file can be a simple hand produced label file. It can also be an existing cube label which contains a Mapping group.

Type	filename
File Mode	input
Default Path	$base/templates/maps
Default	$base/templates/maps/simplecylindrical.map
Filter	*.map *.cub

Description

This file will contain the sky as a map projected image.

Type	cube
File Mode	output
Filter	*.cub

Description

This parameter is used to specify how the scale is obtained for the output map projected cube.

Type	string
Default	CAMERA
Option List:	Option Brief Description CAMERA Compute resolution from input cube This option will automatically determine the scale from the input cube specified using the FROM parameter. Exclusions SCALE MAP Read scale from input map file This option will use the Scale (pixels/degree) in the map file. Exclusions SCALE USER Get scale from user This option allows the user to specify the resolution using the SCALE parameter. The scale should be entered in pixels/degree. Inclusions SCALE

Description

The number of pixels per degrees (RA/DEC). By default, the program attempts to compute this value as 1 / IFOV of the camera. Note you will typically need to convert IFOV in milli-or-micro radians to degrees. Alternatively, you can entered the scale in the MAP file in pixels per degrees (1 / IFOV). That is,

              Group = Mapping
                ...
                Scale = 17000.0
              End_Group
              End_Group
            

Type	double
Minimum	0.0 (exclusive)

Description

This parameter is used to specify how the default ra/dec ground range for the output map projected image is obtained. Note the user can overide the default using the SRA, ERA, SDEC, EDEC parameters.

Type	string
Default	CAMERA
Option List:	Option Brief Description CAMERA Compute default range from input cube This option will automatically determine the mininum/maximum ra/dec from the input camera model cube specified using the FROM parameter. MAP Read default range from map file This option will read the mininum/maximum ra/dec from the input map file. All four values are expected to be defined.

Description

The starting right ascension of the sky map. If not entered it will be read computed from the CAMERA or read from the MAP file, depending on the option chosen for DEFAULTRANGE. If this value is entered, it will override the default value.

Type	double
Internal Default	Use default range
Minimum	0.0 (inclusive)
Maximum	360.0 (inclusive)

Description

The ending right ascension of the sky map. If not entered it will be read computed from the CAMERA or read from the MAP file, depending on the option chosen for DEFAULTRANGE. If this value is entered, it will override the default value.

Type	double
Internal Default	Use default range
Minimum	0.0 (inclusive)
Maximum	360.0 (inclusive)
Greater Than	SRA

Description

The starting declination of the sky map. If not entered it will be read computed from the CAMERA or read from the MAP file, depending on the option chosen for DEFAULTRANGE. If this value is entered, it will override the default value.

Type	double
Internal Default	Use default range
Minimum	-90.0 (inclusive)
Maximum	90.0 (inclusive)

Description

The ending declination of the sky map. If not entered it will be read computed from the CAMERA or read from the MAP file, depending on the option chosen for DEFAULTRANGE. If this value is entered, it will override the default value.

Type	double
Internal Default	Use default range
Minimum	-90.0 (inclusive)
Maximum	90.0 (inclusive)
Greater Than	SDEC

Description

If this option is selected, pixels outside the ra/dec range be trimmed or set to null. This is useful for certain projections whose lines of latitude and longitude are not parallel to image lines and sample columns.

Type	boolean
Default	FALSE

Description

This is the type of interpolation to be performed on the input.

Type	string
Default	CUBICCONVOLUTION
Option List:	Option Brief Description NEARESTNEIGHBOR Nearest Neighbor Each output pixel will be set to the pixel nearest the calculated input pixel. BILINEAR Bi-Linear interpolation Each output pixel will be set to the value calculated by a bi-linear interpolation of the calculated input pixel. CUBICCONVOLUTION Cubic Convolution interpolation Each output pixel will be set to the value calculated by a cubic convolution interpolation of the calculated input pixel.