Elevation

If you are making a measurement to an elevated horizon you need to consider the effect this will have on the bearing.  It is possible to make precise calculations regarding elevation if you are constructing your own orthographic projection diagrams.  Alternatively, with a little practice and a good understanding of the motion of the object you can make rough adjustments in the field.



The diagram above shows how elevation affects where the sun or moon will come up in the northern hemisphere.  You can see that any elevation will shift the point of rise to the right (south).  If you are calculating where the sun will go down on a particular day in the northern hemisphere, remember that setting objects move from top left to bottom right so actual bearings occur further to the left (also south) than theoretical ones.
As it is 'impossible' to reckon elevation by eye alone, it is important to make sure you always measure elevation. Some magnetic compasses (like the one in the previous page) come with a pendulous arm which can be used with
the bezel and mirror to make relatively accurate elevation measurement.
The simplest simple way to measure elevation is with a plumb line and a protractor as shown below.

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