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Determination of azimuth

To determine the declination of an direction one needs to measure the azimuth and the apparent altitude.
Several way can be followed to determined the azimuth of a particular building. There are generally three different ways to determine the azimuth:

from one point (A: like with a compass, photometry or reference object)
using two points from behind the desk (A and B: like with an map or ground plan)
using two points (A and B: like with a GPS)

The methods and tools used with these ways are discussed in more detailed on this web page. If one is in open air most of the mentioned tools are easily used. Don't forget to measure the (apparent) altitude as accurate as possible!!!
But as soon as one has to determine e.g. the average direction of a passage or the sunniness of a building, one has problems because a GPS and a compass don't work inside a building and an ordinary map will not provide any input for this kind of activity.
The ways that could be used in this instance are:

Use a good ground plan of the building (from literature or made yourself). Remember that an accurate direction must be provided by this groundplan (like true north). Information from groundplan can be inputten in the sunniness/mooniness page to determine the azimuth.
Make an extension of the to be measured azimuth to the outside of the building (using a long string or a laser pen). In that way one is able to use the compass to get the azimuth_c. If one wants to determine azimuth_l with a GPS, the end string or laser light (point B) must be at least some 800 m away from point A to get an accurate measurement (+/- 15').
Try to find in the distance a reference object (point B), that is in line with the azimuth to be determined. One can determine the location of this object (point B) by travelling to it and then use the GPS to gets azimuth_l or one can try to find the object on a map to get azimuth_m. Remember that point B must be at least 800 m for GPS and at least some 1.6 km for map.
Two persons are needed: One is in the building (point A) and looking outside in the correct azimuth, the other person walks with a GPS some distance away (more than 800 m) in such a way that it is line of the azimuth. Now point B can be determined (as far as possible from point A) and thus azimuth_l.
The shadow of a celestial body can also be used to determine this (certainly when determining the sunniness/mooniness). The azimuth_s of the sun/moon can be determined by ephemeris programs. Remember that these programs determine the middle of the celestial object and normally the shadow is determined by the left or right rim of the object (for moon and sun this is around 16' difference).

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Last major content related changes: July 22, 2000