urn:nasa:pds:magellan_gvdr:data_gvdr:gvadf_sinu 1.0 1.23.0.0 Product_Observational Magellan Mission urn:nasa:pds:context:investigation:mission.magellan data_to_investigation The Magellan Spacecraft Host urn:nasa:pds:context:instrument_host:spacecraft.mgn is_instrument_host Magellan Spacecraft Radar System Instrument urn:nasa:pds:context:instrument:mgn.rdrs is_instrument Venus Planet urn:nasa:pds:context:target:planet.venus data_to_target GVDR 376 5747 Stanford Center for Radar Astronomy gvdr_0001 Table cartography_parameters_to_image_object 0.00 360.00 90.00 -90.00 Sinusoidal 0 Coordinate Pair 18.225 18.225 5.79478 5.79478 -9.1125 9504.3375 Planetocentric 6051.0 6051.0 6051.0 Positive East urn:nasa:pds:magellan_gvdr:document:gvdrsis data_to_document urn:nasa:pds:magellan_arcdr::1.0 data_to_derived_source_product gvadf.tab 1994-05-10T23:12:06.000 Table 0 1329478 The GVADF file contains estimates of the planetary radius and large-scale surface statistics derived from the altimeter echoes by a template-fitting procedure. The ADF acronym stands for 'Altimetry Data File', one of the data files in the ARCDR data product. This file is a table; each row in the table summarizes ADF results in a particular altimetry viewing geometry. The location and number of rows associated with each pixel are given by the corresponding values of 'ADF Start' and 'ADF Samples' in GVPIDX.TAB. See the descriptions in the GVTIDX.LBL and GVPIDX.LBL files for the overall organization of the GVDR. These files describe the division of the planet into pixels and organization of pixels into rectangular tiles. 7 0 10 Sample Count 1 1 UnsignedMSB2 2 The total number of ARCDR ADF footprints used to compute the estimates of radar scattering properties given in this row of the table. The quantities given in later columns pertain only to these footprints. Any altimetry footprint that is partially or completely contained inside this pixel is included. (Only the small inner portion of altimetry footprints is considered for inclusion; this is the portion described by the ARCDR ADF fields 'Along_Track_Footprint_Size' (alias AR_XFOOT) and 'Cross_Track_Footprint_Size' (alias AR_YFOOT). This does not include altimetry footprints that illuminated this pixel but did not do so from directly above.) Radius Mean 2 3 UnsignedMSB2 2 km 0.000457806 6040 The mean planetary radius of all the footprints used in this row. The radius is obtained from the 'Derived_Planetary_Radius' field (alias AR_RADIUS) in the ARCDR. Radius Variance 3 5 UnsignedMSB2 2 km squared 7.63009e-05 The unbiased estimate of the variance of the planetary radius of all of the footprints used in this row. The radius is obtained from the 'Derived_Planetary_Radius' field (alias AR_RADIUS) in the ARCDR. The variance estimate gives an indication of the topographic relief across the pixel. The unbiased estimate is obtained from the following formula: 'Radius Variance' = 1/(N-1) * ( SUM(X_i^2) - 1/N * [SUM(X_i)]^2 ) where N = 'Sample Count' above X_i = samples of radius AR_RADIUS, i = 1,2,...,N. Slope Mean 4 7 UnsignedByte 1 degree 0.06 The mean surface rms slope of the footprints used in this row. The rms slope is obtained from the 'Radar_Derived_Surface_Roughness' field (alias AR_SLOPE) in the ARCDR, and is based on the Hagfors model of rough surface scattering. Slope Variance 5 8 UnsignedByte 1 0.02 -3 The unbiased estimate of the variance of the rms slope of all of the footprints used in this row. The rms slope is obtained from the 'Radar_Derived_Surface_Roughness' field (alias AR_SLOPE) in the ARCDR, and is based on the Hagfors model of rough surface scattering. The variance estimate gives an indication of the surface roughness variability across the pixel. The unbiased estimate is obtained from the following formula: 'Slope Variance' = 1/(N-1) * ( SUM(X_i^2) - 1/N * [SUM(X_i)]^2 ) where N = 'Sample Count' above X_i = samples of slope AR_SLOPE, i = 1,2,...,N. The units of this measurement are degrees-squared, but the value stored in the table is the base-10 logarithm of the true value. To obtain the true value, apply the scaling and offset given above and raise 10 to this power. Reflectivity Mean 6 9 UnsignedByte 1 0.01 -2.5 The mean surface bulk reflectivity of the footprints used in this row. The bulk reflectivity is obtained from the 'Derived_Fresnel_Reflectivity' field (alias AR_RHO) in the ARCDR, and is based on the Hagfors model of rough surface scattering. The value has not been adjusted by the diffuse scattering correction term 'Derived_Fresnel_Reflect_Corr' (alias AR_RHOCOR). The units of this measurement are dimensionless, but the value stored in the table is the base-10 logarithm of the true value. To obtain the true value, apply the scaling and offset given above and raise 10 to this power. Reflectivity Variance 7 10 UnsignedByte 1 0.028 -7 The unbiased estimate of the variance of the surface bulk reflectivity of the footprints used in this row. The bulk reflectivity is obtained from the 'Derived_Fresnel_Reflectivity' field (alias AR_RHO) in the ARCDR, and is based on the Hagfors model of rough surface scattering. The value has not been corrected with the diffuse scattering correction term 'Derived_Fresnel_Reflect_Corr' (alias AR_RHOCOR). The variance estimate gives an indication of the surface reflectivity variability across the pixel. The unbiased estimate is obtained from the following formula: 'Reflectivity Variance' = 1/(N-1) * ( SUM(X_i^2) - 1/N * [SUM(X_i)]^2 ) where N = 'Sample Count' above X_i = samples of slope AR_RHO, i = 1,2,...,N. The units of this measurement are dimensionless, but the value stored in the table is the base-10 logarithm of the true value. To obtain the true value, apply the scaling and offset given above and raise 10 to this power. gvadf.lbl 0 PDS3 Original PDS3 label Carriage-Return Line-Feed gvadf.fmt 0 PDS3 Original PDS3 format file Carriage-Return Line-Feed