DATA_SET_DESCRIPTION 
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 roversized 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 RATsized patch and is intended for use with
IDD operations, while the surface normal used in slope
calculations is based on a roversized 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 singleband floatingpoint 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 singleband floatingpoint 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 sideslope). 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((xx0)^2 + (yy0)^2)
Vy = (y  y0) / sqrt((xx0)^2 + (yy0)^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 XY 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 singleband floatingpoint 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 eastfacing 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 singleband floatingpoint 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 1A), Level 4 (Resampled Data
equivalent to NASA Level 1B), or Level 5 (Derived Data
equivalent to NASA Level 1C, 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
metadata 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 multiframe (mosaic)
form. Most RDR data products will have PDS labels, or if generated
by MIPL (OPGS), dual PDS/VICAR labels. Nonlabeled 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.
