48 Remote Sensing/Geographic Info System

Sunday, 9 October 2011
1:30 PM - 5:30 PM
Room M100BC

ALOS/PALSAR SUBSURFACE IMAGING OF A BURIED FOUNDATION IN THE WESTERN DESERT, EGYPT

Paper number: 48-3
Program: Technical Sessions
Time: 2:00 PM – 2:15 PM

Authors

Abstract

ALOS/PALSAR L-band full polarimetric data have been used to detect and characterize a well-defined geometric target hidden under sand deposits in the Western Desert of Egypt. This buried object is rectangular in shape with very straight boundaries and encloses an area of 500 m². Inside the rectangular area there is a perfectly circular feature of approximately 53 m² area. High resolution optical satellite images (WorldView-2) and field investigation confirm that the topography of the study area is relatively flat and completely covered by dry sand. The electromagnetic wave scattering behave of this detected buried object was measured by decomposing the scattering matrix of ALOS/PALSAR full polarimetric data into Entropy-Alpha (H/ α) and Freeman and Durden decompositions. Therefore, a combination of unsupervised classification algorithms and Constant False-Alarm Rate (CFAR) edge detection was performed using ALOS/PALSAR full polarimetric data and revealed a well-defined geometric shape with straight borders. These borders have high α angle with low entropy, which physically means double bounce scattering mechanism with low randomness. Such scattering mechanism of the buried object behaves very similar to an urban scatterer, indicating that the detected target might be a buried wall-like foundation of a man-made structure.

The moisture contents (ӨS) of the first top 30 cm of the soil were measured in 20 locations of the study area and showed generally very low (near 0%) moisture contents. The average Root Mean Square Height (hRMS) of the surface roughness was also low with 0.017 cm across all sites. The relative dielectric constant (εr) of the sand in the study area produced a very low value of 3.0. The effects of ӨS, εr and hRMS on the radar backscattered signals as measured in the study area turned out to be very low and, thus, provide good conditions for L-band to penetrate relatively deep into the ground. Moreover, 28 GPR profiles were acquired using a 270 MHz shielded antenna to validate the satellite radar remote sensing results. The GPR profiles reveal very clear hyperbolic shapes at 2 m depths. A very promising large hyperbolic shape-like structure appears in profile 7, which might indicate the presence of a buried foundation.