Using Shadows in Image Geolocation: Method and Limits
Shadows can help evaluate a geolocation hypothesis when the image, terrain and time context are understood.
Establish the image context
Keep the original image and document its source. Inspect possible rotation, mirroring, lens distortion and editing. An apparent direction in the image is not a compass bearing until orientation has been established using independent landmarks.
Build a candidate location
Compare roads, buildings, slopes and horizon features with mapping or imagery sources. Record why a candidate fits and what remains inconsistent. Use a common coordinate reference and acknowledge the age or resolution limits of the comparison imagery.
Use sun geometry carefully
If a date and reliable orientation are available, compare shadow direction with a solar-position model. Shadow length also depends on object height and terrain. A single shadow generally cannot determine a unique place and time without additional assumptions.
Communicate uncertainty
Present the evidence supporting the candidate and the assumptions used in the calculation. Give a range when the inputs do not support a precise time. Avoid presenting an unverified location as a confirmed sighting; the goal is a defensible assessment that another analyst can review.
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