US 4,890,249 A · Data compression and decompression for digital radar landmass simulation

Abstract

A unique digital radar landmass simulator (DRLMS) uses different culture data compression techniques and hardware from that used in the conventional DRLMS systems. The application of these techniques to DRLMS results in a system that is small in size and high in performance. During the data base preparation, Defense Mappinig Agency (DMA) Digital Terrain Elevation Data (DTED) and Digital Feature Analysis (DFAD) data are processed and compressed for elevation, reflectivity and aspect channels with different compression schemes. The compressed data is then stored on disks for each channel. Dedicated decompression hardware for each channel then retrieves, decompresses, and reconstructs the data. The culture compression and decompression hardware uses a run length compression technique that results in the capability of presenting a very detailed culture map for the terrain. The elevation compression uses a table look-up technique that generates high resolution terrain data. The coordination of the timing of the several channels in order to generate the final display is accomplished by designating one of the channels as a master channel to maintain synchronism among the channels.

Claims12

Dependent claims

A method of real time data retrieval in data radar landmass simulation comprising the steps of:

compressing off line digital feature analysis and digital terrain elevation data as compressed aspect, elevation and reflectivity data bases for the simulation;
separately storing the compressed aspect, elevation and reflectivity data bases for later access and decompression for the simulation;
synchronously and continuously accessing the compressed aspect, elevation and reflectivity data and decompressing and temporarily storing the decompressed data;
generating radar incident vectors;
processing the temporarily stored aspect data to produce surface normals and calculating vector dot products between said radar incident vectors and the surface normals to generate radar aspect returns;
processing the temporarily stored elevation data and calculating shadowing due to elevation and slant range as a function of ground range;
and
processing the temporarily stored reflectivity data, the calculated radar aspect returns, shadowing and slant range and calculating terrain radar return.

5 more elements

A digital radar landmass simulator comprising:

first, second and third channels for storing respectively compressed aspect, elevation and reflectivity data and synchronously and continuously retrieving and decompressing said compressed data in real time, each of said channels including a microprocessor operating as a channel controller, the microprocessors of said channels being connected to a common bus, one of said microprocessors being a master microprocessor and maintaining synchronism of said channels;
means for generating a scan and depression angles and computing radar incident vectors;
aspect computer means connected to said first channel and responsive to decompressed aspect data for processing the data to produce surface normals and calculating vector dot products between said radar incident vectors and the surface normals to generate radar aspect returns;
shadowing and converter means connected to said second channel and responsive to decompressed elevation data for calculating shadowing due to elevation and slant range as a function of ground range;
radar equation means connected to said third channel, said aspect computer means and said shadowing and converter means and responsive to decompressed reflectivity data, said calculated radar aspect returns, shadowing and slant range for calculating terrain radar returns;
and
display means connected to said radar equation means and responsive to said calculated terrain radar returns for displaying a simulated radar image.

4 more elements

Dependencies are inferred from the claim text.

Data compression and decompression for digital radar landmass simulation

Life of this patent

Data compression and decompression for digital radar landmass simulation

Life of this patent

Abstract

Claims12