locationshadowastronomy

Approximately find the location using the direction of shadow, UT and date

Is anyone with an idea about finding location using by direction of shadow (for example azimuth angle), 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 northern hemisphere direction of shadow is to north. and I tell also by attention to time and date, however these points of the world were dark so that was a wrong turn.
Is anyone with an great ideas for limiting the area of guess?

example

Solution

  • Simple approach for start

    What I have in mind with those comments was something like this:

    latitude

    1. locate&select measurable shadow edge (left image)
      • try to use tall buildings and long shadows to increase accuracy
    2. create 3D representation of it (middle image)
    3. compute sun position (yellow) for time the shot was taken (right image)
    4. from angle b between To Sun and surface normal you can obtain a cone
      • intersection of it with the surface will give you circle of possible locations

    5. now just find the location on the circle in which the (red) North vector points to North pole while Normal lies on the cone and surface projection of (green) To sun points to middle of circle

      enter image description here

    All of this is not tested (never tried this) it is just an overview how I would start to approach this

    [Notes]

    The image is not corrected so you need to take into account that x,y axises of image are angular (FOV of camera) not cartesian !!!

    The height of building can be approximately obtained by counting the number of floors, or comparing to something known like Car/Bus height, Traffic sign,etc

    see selection criteria for different projections