INTRODUCTION

GRIDDING SCHEME

• Sprint combines the eight sample points (two in azimuth by two in elevation by two in range) surrounding an output grid point.  This three-dimensional linear interpolation scheme means that Sprint adapts itself to the local sampling resolution in the original radar range-azimuth-elevation sampling domain.  However, it does mean that near the radar several beams of data will never be used when the output grid resolution is larger than the original sampling resolution.  The option to filter (smooth) the data in radar space before doing the actual interpolation will help use nearby samples to reduce measurement errors.  The Reorder distance-weighting scheme should be viewed as a filtering or smoothing operation that is evaluated at the output grid point and is not a true interpolation.
• There are options to transform quantities such as radar reflectivity factor (dBZ) from the dB scale to a linear one before these input measurements are interpolated.  Once the interpolation is completed, these linear values are converted back to a dB scale.
• There is also an option to do local unfolding (JTech-Sprint.pdf)before interpolation of the surrounding eight radial velocities to the output grid point.

CODING DEFICIENCIES

• When more than eight fields are interpolated and one of these is a velocity field with local unfolding (UNFOLD option), the QUAL field that is a normalized measure of the quality of the estimated grid point value is messed up.  The QUAL field is not essentially to the analysis of single radar datasets nor is it used in the wind synthesis.  Until this problem is fixed, the Sprint user should make two runs of Sprint, one with less than eight fields and including velocity with local unfolding and one with the remaining fields needed for analysis.  These two runs can be easily combined in Cedric with a READVOL followed by a TRANSFER command to assemble both runs into a single Cedric output volume (WRITVOL command).
• Coded for interpolation of ELDORA datasets, but currently this option does not work.  The program runs to completion but there is no interpolated data in the output file.

MODIFICATIONS

SAMPLE SCRIPTS