- SPECIAL REPORTS
- THE MAGAZINE
Surveying Coordinate Systems: Astronomical Coordinate SystemsWhich astronomical coordinates are constantly changing and can readily be measured by a theodolite?
A. right ascension and declination
B. hour angle and declination
C. hour angle and parallactic angle
D. altitude and azimuth
The altitude and azimuth of a celestial body can be measured with respect to the observer's horizon and astronomic north. An instrument such as a theodolite can be successfully oriented to these references with relative ease. The references of the other astronomic coordinates include the First Point of Aries and the celestial equator, among others. It would be considerably more difficult to orient a theodolite to such references.
The answer is D.