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Digital Archive of Toyo Bunko Rare Books
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| 0176 |
Memoir on Maps of Chinese Turkistan and Kansu : vol.1 |
Citation Information
OCR Text
METHOD OF REDUCTION, 1913-15 JOURNEY
Hypsometer readings, corrected for thermometer scale-error, were reduced to equi-
valent air pressure, and these were treated as fully corrected. Mercury barometer readings
were corrected for scale-error and reduced to freezing point. Aneroid readings were treated
as fully corrected. In this way each instrument yields a fully corrected pressure.
Next from a table, based on the International Meteorological Formula (1905) the
height above a standard pressure level, 29·92, was read off. The result was multiplied by a
factor, taking account of the mean air temperature. By means of the Indian Daily Weather
Report chart, the value of pressure at sea-level at the station is estimated. Its difference
from the value 29·92 multiplied by 873 is the necessary correction to the height in feet.
The differences between results of aneroid and mercury barometer were taken out, and applied
to succeeding aneroid readings until the next comparison occurred. The same would have
been done for the hypsometer results, if it had been decided to retain them.
MISTAKES OF COMPUTATION
By a mistake on the part of the computer, uncorrected aneroid heights were given in
four cases in place of the corrected mercury heights. Places and corrections are as follows.
Place Height given Correction Final height
Toghrak-bulak 2740 + 97 2837
Besh-toghrak 1980 + 32 2012
Kum-kuduk 2150 + 95 2245
Lowaza 1890 +147 2037
RECORDS AND COMPUTATIONS
These are at Dehra Dûn, in the Computing Office, Survey of India, and are available
for reference.
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