Re: Measuring angles in an image.

Say, I have taken the image of certain area covering 50 meters
square. My principle point being a building top corner , I need
to get
the angle it makes with a target object ,say a flag pole top
with respect to principle axis . To locate the point I will need to
zoom until the pixels pops as a means to get
the accuracy . Does that disturb the spatial calibration ? Remember
that I am working on image that is already captured.
If I don't zoom the image I am left with poor accuracy . Zooming
often arises a question in my mind ( Does "zooming in" in
common image viewers means that you are going beyond 100% , that
again creates the problem because if the application is performing a
sort of rendering ( digital zoom) I loose original contents of my
image and what I focus may resemble nothing in real world ).

Regarding spatial calibration , I work the real distance between two
image elements , note how many pixels it occupies and then I can
easily work distances on other photographs too if they were taken
at same distance as former one and that same camera was used
( excluding the lens distortions and environmental parameters ) .
But
the distances are only correct if they lie in the same plane of the
reference object . For example, if my flag pole is far behind the
building , on image they have small spatial separation but in
reality they are far from each other. This gives a thought of DN,
value of the elements , can that be incorporated to find the real
distances.

Regards ,

Geobird
.

Relevant Pages

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