150 
1B 10 km 
Figure 1A. Shuttle Radar Image over Esfideh, Horasan 
province (East Iran). 
Figure 1B. Shuttle hand-held photography over same 
area. Notice the differences in length of the strike 
ridges between a and b on the two images. 
color image of the Linhof camera. The ridges can be 
followed over 16 km running parallel to the flight 
track of the shuttle before they disappear towards 
the east under superficial fan material. This super 
ficial cover forms a uniform tonal area on the space 
photo intersected only by two not very well express 
ed dry river valleys having a "V" shape (fig. 1B at 
c and d). 
The eastern branch is clearly discernible also on 
the radar image (fig. 1A at a) as a lighter-toned 
zone because of difference in surface roughness 
between the dry riverbed, with relative coarse ma 
terial, and the smooth surface of the more sandy fan 
material. A vague gulley pattern typical for a 
desert fan is present. 
The western branch of the riverbed is only very 
faintly visible on the radar (fig. 1A at c). 
The Eocene to Oligocene strike ridges can be follow 
ed on the radar image over a length of 28 km, which 
is 12 km longer than the distance measured on the 
photo image, although over the last 12 km the tonal 
contrast on the radar between the two horizons and 
the surrounding material is less distinct. 
There remains the question if spatial resolution 
of the Linhof camera may not be insufficient to 
allow for further discrimination of these two hori 
zons. It seems clear that the outcrops are not con 
tinuing as strike ridges, but they may continue as 
concentrations of loose rock material on the pedi 
ment slope or sand sheet, although no tonal differ 
entiation on the photo suggests this possibility and 
a thin sand cover is more likely. The author has 
neither succeeded in obtaining ground information 
nor in obtaining aerial photographs over this area 
to study the differences in more detail to come to 
convincing conclusions. 
SUDAN/EGYPT 
In the area of the Red Sea hills (Sudan) and east 
ern desert (Egypt), a comparison was made of SIR-B 
radar data, Landsat and Large Format Camera (LFC) 
images. The spatial resolution of the radar data 
and the LFC photos is approximately of the same 
order (Table 1). So they were the index components 
in the comparison (fig. 2). 
Table 1. Ground resolution of RS-data. 
Shuttle Imaging Radar - azimuth resolution: 29.4 m 
(4 look) SIR-B range resolution : 17.8 m 
Landsat 3 MSS - 80 m 
Large Format Camera (LFC) - 15-20 m 
(film B/W 3412) 
The Large Format Camera has the further advantage 
that topographic height differences can be observed 
by stereo viewing of overlapping photographs, in 
creasing the confidence level of interpretation. 
The radar data were acquired during the 17th 
shuttle flight (SIR-B mission) data take 097.5 on 
12 October 1984. The radar incidence angle was 
52.1° towards the beam center. In contrast with 
SIR-A where only optical processed data were avail 
able, SIR-B allowed digital correlation. 
GEOLOGY OF THE RED SEA HILLS 
The oldest rocks occurring in the area are the 
granitic gneisses and amphibolites of the Lower- 
Middle Proterozoic Kashebib Group (Vail, 1979), 
referred to by Gabert et al. (1960) as Kashebib 
series. The rock sequence also occasionally con 
tains some marbles. They are correlated with the 
Mitig gneisses from the Egyptian eastern desert 
(Said, 1971; Schurmann, 1974). 
The sequence forms in general a high relief. A 
coarse metamorphic trend direction is visible on 
Landsat and LFC photographs. The tone of the out 
cropping rocks on the B/W LFC photos is slightly 
dark but less so than the ultrabasic and basic rock 
types. 
The Kashebib group is followed upwards by the 
Nafirdeib group (Ruxton, 1956) consisting of meta 
sediments and acid to basic metavolcanites. They 
form a typical green schist assemblage with occa 
sional ultramafic masses and serpentinites. Hashad 
(1980) gives an age of 1200 Ma on the basis of 
radiometric Rb/Sr measurements for similar rock 
types in the eastern desert op Egypt. 
The metasediments and metavolcanites are well re 
cognizable on the remote sensing images as a result 
of their metamorphic texture. Finely aligned meta 
morphic strike ridges are typical for these rocks. 
Relief is in general rather subdued and intricate 
fold structures can be recognised. The ultramafic 
rocks are very dark in tone on Landsat MSS and LFC 
images. 
The Proterozoic intrusive rocks consist of older 
batholitic granites, granodiorites, thonalites and 
pegmatites. These rocks are often mildly foliated. 
They form intrusive contacts with the metasedimen 
tary sequence. The ages of the older granitoids are 
given by Hashad (op.cit.) as 1000-850 Ma for the 
egyptian part. Most of the granodioritic batholiths 
in Sudan are assigned a slightly younger age (700 
Ma) . These granitoid bodies have a very subdued 
relief due to intensive weathering (Dixon, 1982). 
They are extensively covered by sand sheets and 
crop out only on the edges of the batholiths. 
These sandy areas appear dark in tone on the radar 
in contrast to the light tones on the MSS and LFC 
images.