Data Set Overview
  =================
 
    Surface Normal for Slopes
    -------------------------
      While the Surface Normal for Slopes product is not archived, it is
      an intermediate product used as an input to the Slope, Slope Rover
      Direction,Slope Heading, and Slope Magnitude products, so it is
      described once here for brevity.
 
      The Surface Normal for Slopes is a unit vector indicating the
      surface normal for each pixel.  It is derived from the XYZ product
      by fitting a plane over a rover-sized patch in physical space for
      every image pixel in the input stereo images. The surface normal
      is then computed (in Site frame) as the normal to the plane fit.
 
      Note that the Surface Normal for Slopes is not the same as the UVW
      product.  While it uses fundamentally the same algorithm, the UVW
      product is based on a RAT-sized patch and is intended for use with
      IDD operations, while the surface normal used in slope
      calculations is based on a rover-sized patch and is intended for
      use with rover driving.  Also, the Slopes version is in Site
      frame, while the UVW product is expressed in Rover frame.
 
      The symbols Nx, Ny, and Nz are used below to indicate the x,y,z
      components of the unit vector for slopes.
 
 
    Slope Map RDR
    -------------
      The Slope Map RDR is a single-band floating-point image that
      represents the predicted slope of the terrain centered around each
      pixel.  It is expressed in units of degrees.  It is computed as
      the elevation of the Surface Normal for Slopes vector with respect
      to the (X,Y) plane in Site frame according to the following
      formula:
 
        slope = (180/pi) * (pi/2 + arctan(Nz / sqrt(Nx^2 + Ny^2)))
 
      A value of 0.0 is used to indicate lack of data.  This can be
      ambiguous in the rare cases that the computed slope is
      exactly 0.0.
 
 
    Slope Rover Direction RDR
    -------------------------
      The Slope Rover Direction is a single-band floating-point image
      that represents the component of the slope centered around each
      pixel that is facing toward the rover at its current position. It
      is intended to indicate the amount of climb the rover would
      experince if it traveled radially away from its current position
      (i.e. ignoring side-slope). It is expressed in units of degrees.
      It is computed from the XYZ image and the Surface Normal for
      Slopes according to the following formula:
 
        Vx = (x - x0) / sqrt((x-x0)^2 + (y-y0)^2)
        Vy = (y - y0) / sqrt((x-x0)^2 + (y-y0)^2)
        srd = -(180/pi) * arctan2((Vx*Nx + Vy*Ny), -Nz)
 
      where x0 and y0 are the X and Y offsets of the Rover coordinate
      system with respect to the Site (ORIGIN_OFFSET_VECTOR in
      ROVER_COORDINATE_SYSTEM group) and x and y are the X and Y values
      from the XYZ image.  Vx and Vy thus make up a unit vector
      representing the direction in the Site X-Y plane of the pixel from
      the rover.
 
      A value of 0.0 is used to indicate lack of data.  This can be
      ambiguous in the rare cases that the computed value is
      exactly 0.0.
 
 
    Slope Heading RDR
    -----------------
      The Slope Heading RDR is a single-band floating-point image that
      represents the compass direction toward which the slope centered
      around each pixel points (clockwise from north).  Thus a value of
      90 indicates an east-facing slope.  It is expressed in units of
      degrees in the range +/-180.  It is derived from the Surface
      Normal for Slopes as follows:
 
        heading = (180/pi) * arctan2(Ny, Nx)
 
      A value of 0.0 is used to indicate lack of data.  This can be
      ambiguous in the rare cases that the computed heading is exactly
      0.0.
 
 
    Slope Magnitude RDR
    -------------------
      The Slope Magnitude RDR is a single-band floating-point image that
      represents the magnitude of the slope centered around each pixel.
      It is a dimensionless number between 0 and 1, and is in fact
      simply the sine of the Slope product. Thus it provides no
      additional information beyond the Slope product but the value may
      be more useful in some circumstances.  Together the Slope Heading
      and Slope Magnitude completely describe the surface normal.  The
      magnitude can be computed two ways:
 
        magnitude = sin(slope)
        magnitude = sqrt(Nx^2 + Ny^2)
 
      The second is used by MIPL software.
 
      A value of 0.0 is used to indicate lack of data.  This can be
      ambiguous in the rare cases that the computed magnitude is exactly
      0.0.
 
 
  Processing
  ==========
    MER Camera Payload RDRs are considered Level 3 (Calibrated Data
    equivalent to NASA Level 1-A), Level 4 (Resampled Data
    equivalent to NASA Level 1-B), or Level 5 (Derived Data
    equivalent to NASA Level 1-C, 2 or 3). The RDRs are to be
    reconstructed from Level 2 edited data, and are to be assembled
    into complete images that may include radiometric and/or geometric
    correction.
 
    MER Camera Payload EDRs and RDRs will be generated by JPL's
    Multimission Image Processing Laboratory (MIPL) under the OPGS
    subsystem of the MER GDS. RDRs will also be generated by the Athena
    Pancam Science and Microscopic Imager Science Teams under the SOAS
    subsystem of the GDS.
 
    RDR data products will be generated by, but not limited to, MIPL
    using the Mars Suite of VICAR image processing software at JPL, the
    Athena Pancam Science Team using IDL software at Cornell University
    and JPL, and the Microscopic Imager Science Team using ISIS software
    at USGS (Flagstaff) and JPL. The RDRs produced will be processed
    data. The input will be one or more Camera EDR or RDR data products
    and the output will be formatted according to this SIS. Additional
    meta-data may be added by the software to the PDS label.
 
 
  Data
  ====
    RDR products generated by MIPL will have a VICAR label wrapped by a
    PDS label, and their structure can include the optional EOL label
    after the binary data. RDR products not generated by MIPL may
    contain only a PDS label. Or, RDR products conforming to a standard
    other than PDS, such as JPEG compressed or certain Terrain products,
    are acceptable without a PDS header during mission operations, but
    may not be archivable.
 
    The RDR data product is comprised of radiometrically decalibrated
    and/or camera model corrected and/or geometrically altered versions
    of the raw camera data, in both single and multi-frame (mosaic)
    form. Most RDR data products will have PDS labels, or if generated
    by MIPL (OPGS), dual PDS/VICAR labels. Non-labeled RDRs include JPEG
    compressed products and the Terrain products.
 
 
  Software
  ========
    The MIPL Mars Program Suite was used to generate these RDRs.
 
 
  Media/Format
  ============
    The data set will initially be delivered and kept online.  Upon
    Mission completion, the Panoromic Camera Operations RDRs will be
    delivered to PDS on DVD.

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