157 
Symposium on Remote Sensing for Resources Development and Environmental Management / Enschede / August 1986 
Geological analysis of Seasat SAR and SIR-B data in Haiti 
Ph.Rebillard 
SEP/DTI, Puteaux, France 
B.Mercier de l’Epinay 
Université PM. Curie, Paris, France 
ABSTRACT : Synthetic Aperture Radar data obtained by Seasat in 1978 and by SIR-B in 1984 were registered to 
the corresponding Landsat MSS data over the Western part of Haiti. Two areas were studied : the island of La 
Gonave and the Miragoane area. Seasat SAR data were registered to the Landsat data over the island of La 
Gonave and both Seasat and SIR-B data were compared over the Miragoane area. 
In both cases, difficulties occured in the interpretation due to the relief which distorted the radar data 
particularly the Seasat data for which the radar incidence angle was 20 degrees ; futhermore, on the Miragoane 
area difficulties occured using the SIR-B data due to low radar signal. 
Structural lines and lithological boundaries were pointed out thanks to the compositional and textual 
informations provided by the radar and MSS data. Geological interpretation maps of La Gonave and the Miragoane 
area were drawn : boundaries between rocks Eocene of age and rough basalts were precised as well as 1) domes, 
2) ancients faults oriented NE-SW, 3) faults oriented NW-SE linked to the La Gonave anticline and 4) faults 
oriented E-W integrated in the tectonic model of the Caribbean plate. 
1 INTRODUCTION 
The Western part of Hispaniola has been 
imaged by Seasat in 1978 and by SIR-B in 1984 
(Fig. 1). Two areas were studied: the 
island of La Gonave and the Miragoane area 
(Southern branch of Haiti). 
Seasat SAR data were registered to the 
Landsat MSS data over the island of La Gonave 
and a map was produced showing the interest 
of compositional and roughness informations 
produced by MSS and Seasat respectively. 
Over the Miragoane area, both Seasat and 
SIR-B data were contrasted to the existing 
maps 
Seasat SAR acquired data at 20° incidence 
angle. In this case, surface slopes played a 
dominant role because of the quasi-specular 
scattering mechanism. Therefore topography 
is strongly highlighted in the Seasat images. 
The effect of foreshortening as well as 
foldover, in some cases, even make topography 
effects more dramatic. 
SIR-B data were acquired with an incidence 
angle of 60°. In this geometry, the 
scattering is mostly dominated by the surface 
roughness at the scale of the wavelength (L 
band = 25 cm). The roughness characteristics 
include both the soil roughness as well as 
the vegetation surficial and volumetric 
roughness. Surface slopes also impact the 
scattered return by modulating the scattering 
from the surface roughness. Surface 
dielectric constant also plays a role in the 
scattered intensity. 
Therefore combined Seasat/SIR-B data contain 
informations on surface topography as well as 
on roughness and provide a better knowledge 
of the surface physical properties. The 
following paper presents our preliminary 
results. 
2 SPACEBORNE DATA 
Seasat SAR data were acquired on August 17, 
1978 during rev. 737. The swath width was 
100 Km and the incidence angle was 23.5°. 
The SIR-B data (data take KI-086.10) were 
obtained in October 1984. The SIR-B swath 
was 14.6 Km wide and the incidence angle was 
60° (Ford et al. 1986). Both Seasat and 
SIR-B were operating in L-band and HH 
polarization. Coverage of the radar paths 
are indicated in Fig. 1. 
Landsat MSS data were obtained on June 29, 
1979 (path 009, row 47). Bands 4, 5 and 7 
were used during the study. 
Figure 1. SAR data coverage, 1: Seasat rev. 
737, 2: SIR-B data take KI-086.10. 
3 DATA REGISTRATION 
The registration of the Seasat and the 
Landsat MSS data over the La Gonave area has 
been made as a pixel to pixel registration 
using the SEP's Vizir Image Processing System 
procedures. The Landsat MSS data image was 
taken as the reference image. Fifty nine 
ground control points were chosen (Rebillard 
et al, 1983 ) . 
Several difficulties occured due to the 
relief of the island and as a consequence, 
the registration is not perfect in the center 
of the study area. 
In the Seasat images (acquired data at 20° 
incidence angle), surface slopes played a 
dominant role because of the quasi-specular 
scattering mechanism. Therefore topography 
is strongly highlighted and the effect of