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Davidson, D. F.

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Preparation of a Geologic Photo Map
and Hydrologic Study of
the
Yemen Arab Republic
G-21990, I.D. #199
D. F. Davidson
U. S. Geological Survey
Quarterly Report
December, 1975
(E76-10246) PREPARATION OF A GEOLOGIC PHGTC 	 N76-20593
MAP AND HYDROLOGIC STUDY OF THE YEMEN ARAB
REPUBLIC Quarterly Report, Dec. 1975
(Geological Survey) '_ p HC $3.50	 CSCL 08F	 UnclasG3/43 00246
al9go
SIS 902.6
E7. e- 1 a24473
VIntroduction
tA
Preparation of a Geologic Photo Map
and Hydrologic Study of the
Yemen Arab Republic
Objectives
The principal purpose of the investigation is to prepare an improved
geologic photo map of the Yemen Arab Republic at's scale of 1:1 million,
or 1:500,000 whichever is feasible within the constraints of time,
L
funds, and imagery quality. 	 The work will be performed largely by
visual inspection of enlarged copy of the various spectral bands using
suitable viewing equipment and interpreting geologic features observed.
In country field trips will be made to establish the validity and photo
appearances of the rock units, and to verify the interpretation of
those units and their structural relations. 	 The trips will also serve
as a test of the validity of hydrogeological interpretation, and should
be helpful in identifying areas for further detailed work.
All of these objectives are being or have been achieved but the
last.	 In part the failure has resulted from the fact that the seasonal
imagery coverage requested has not been available.
Techniques
The techniques used to this time have largely been interpretation of
black and white prints and transparencies on a light table, and
compilation of a geologic map based on such interpretation.	 Field
checks have largely been aimed at resolving stratigraphic and
structural problems which can not be straightened out b1 image inspection.
Accomplishments
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The principal accomplishment to date is the virtual completion
of 7 1:500,000 geologic and structural interpretations of LANDSAT
images which will soon be provided to theGovernment of Yemen for their
use. The interpretations are accompanied by copies of the imagery
itself. Many but not all of the problem areas shown on the inter-
pretations have been field checked.
It is anticipated that following further field checking the geologic
and tectonic interpretations will be recompiled at 1:1,000,000 and pub-
1#ehee in the format of a colored geologic map.
Data Quality and Delivery
After a very slow start data delivery has been excellent, and
data quality good to excellent. We have no complaints on either score,
other than loss of originally requested seasonal data.
Conclusions
Use of LANDSAT data is permitting us to prepare in a very short
time and at low cost a usable geologic map of an area which is largely
inaccessible. The fact that we have been as successful as we have
has encouraged us to use the same approach in other areas of the world.
.	 2


Preparation of a geologic photo map and hydrologic study of the Yemen Arab Republic

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