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 formulae:  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 Navigation Camera Operations RDRs will be delivered to PDS on DVD.

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