RAMCAR-98. CARABAS VHF-band SAR. Final report

Authors:

  • Ulander Lars M.H.
  • Larsson Björn
  • Gustavsson Anders
  • Frölind Per-Olof
  • Jonsson Tommy
  • Stenström Gunnar

Publish date: 2001-01-01

Report number: FOI-R--0177--SE

Pages: 67

Written in: English

Abstract

The French-Swedish RAMCAR-98 experiment was conducted in May 1998 at two test sites in southern France. The Swedish CARABAS-II VHF-band SAR participated together with the French RAMSES multi-frequency SAR. This report summarises the data collection as well as processing and analysis of the CARABAS images. Data from all flight tracks have been successfully processed and the radiometric calibration is based on in-scene reference trihedrals. Image quality varies slightly from image to image. The main problems encountered are due to antenna back-lobe leakage but the quality also depends on the success of filtering the radio-frequency interference. The radar-cross section of deployed vehicle targets, located both in the open and under foliage, was measured for different aspect and incidence angles. All measurements varied in the range 1-20 dBm2, with the smallest values observed for vehicles in forest concealment and for the largest incidence angle. Trihedrals deployed inside different forest stands enabled the two-way attenuation to be measured, giving a maximum value of 2.9 dB. Change detection was found to be a robust method for concealed target detection in CARABAS images since the radar backscattering from trees and other natural objects is relatively low and has a high spatial and temporal correlation.