Does anyone know how to find a location by using :

  1. the direction of shadow relative to the normal (for example azimuth angle)
  2. the Universal time (UT) and date

I have a satellite image and I know north, time and date. One of the cues that I can use is, for example, in the northern hemisphere the direction of shadow is north.

Would anyone know if it were possible, and how, to calculate the location based on these parameters?


1 Answer 1


Planetarium software, such as Stellarium, or astronomical computation software such as pyephem can compute the exact position of the sun at any date, time and location. It is then simple trigonometry to calculate the length of a shadow:

if the sun is $\theta$ degrees above the horizon, a vertical building of height $h$ will cast a shadow on horizontal ground of length $\frac{h}{\tan(\theta)}$.

  • $\begingroup$ Hello James, thank U for answering this question. and so the important point is that I haven't the position. the parameters that I have is direction of shadow and UT and date. $\endgroup$ Oct 12, 2015 at 5:41
  • $\begingroup$ Perhaps you could include the shadow length and direction, the time and date in your question. The answer is essentially the same, you just need to work backwards. Either by hand trial and improvement in stellarium, or more exactly in pyephem. $\endgroup$
    – James K
    Oct 12, 2015 at 18:53

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