ELECTRONIC WARFARE SOUTH AFRICA 2017International Conference & Exhibition6-8 November 2017 | CSIR, Pretoria

ELECTRONIC WARFARE SOUTH AFRICA 2017International Conference & Exhibition6-8 November 2017 | CSIR, Pretoria

The Compression of Raw

SAR Data

Chané Pieterse – University of Pretoria & CSIR

Richard Focke – CSIR

Warren du Plessis – University of Pretoria

The Compression of Raw SAR Data

• Using Block Adaptive Quantisation (BAQ)

Context

• Why compress?

• Size/Weight/Power limitations of platform

• Higher resolution capabilities -> Higher data volume

• Limited onboard storage capacity

• Limited downlink capacity for real-time transmission

• Applications

• Research can be applied to phased arrays

• Data volume reduction

1

Background

• Challenges of compressing raw SAR data:• High entropy value

• High dynamic range

• No statistical redundancy to exploit

• Noise-like Gaussian characteristics of I & Q components

• Non-stationary (samples are uncorrelated)

• Presence of speckle

• Previous work• Theoretically implemented algorithms: BAQ, BFPQ, VQ, Wavelets, Compressive

Sensing, Quantization in Transform Domain

• BAQ used for Magellan mission to Venus

• BFPQ used in the Spaceborne Imaging Radar (SIR-C) mission

• ECBAQ used for ENVISAT

• FDBAQ used in Sentinel 1

2

Implementation

• Data Sets

• ERS-2 set (Spaceborne, C-band, mid-urban data)

• DST SAR sets (Airborne, C-band, pulsed & FMCW, low-urban & mid-urban data)

• Simulated SAR data

• BAQ algorithm

I BlockI component

Determine statistics of

block

Q BlockQ component

Lloyd-Max Quantizer

Raw Complex

Data

Encoded I component

Encoded Q component

3

Results – ERS-2 Data Set

4

Uncompressed – 5 bits Compressed – 4 bits

Results – ERS-2 Data Set

5

Uncompressed – 5 bits Compressed – 1 bit

Results – DST SAR Data Set (Farm)

6

Compressed - 4 bitsUncompressed – 12 bits

Results – DST SAR Data Set (Farm)

7

Compressed - 1 bitUncompressed – 12 bits

Results – DST SAR Data Set (Pecan Wood)

8

Compressed - 4 bitsUncompressed – 12 bits

Results – DST SAR Data Set (Pecan Wood)

9

Compressed - 1 bitUncompressed – 12 bits