
Ask HN: Counting # of protestors? - mtgentry
I was at the anti-trump rally in Los Angeles today. The LAPD estimated the crowd size to be 8,000 however that number seemed very low to me. I&#x27;m wondering if anyone has some software than can look at footage to estimate crowd size. There are a few shots that capture the majority of the protest today like this: https:&#x2F;&#x2F;instagram.com&#x2F;p&#x2F;BMuxQDcjdI4&#x2F;<p>Would love to have a hard count of how many ppl were there - not an estimation!
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martin_a
You can post the image to an imageboard of your choice and write that those
are 8.000 people. Somebody won't trust you and count it.

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matt4077
I remember stories about this from the Obama inauguration. IIRC, someone
(google?) used areal shots, divide it into segments, assign those segments to
different densities, and count the people in samples from all densities.

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chewxy
relevant: [http://www.popularmechanics.com/science/a7121/the-curious-
sc...](http://www.popularmechanics.com/science/a7121/the-curious-science-of-
counting-a-crowd/) and [http://www.gkstill.com/Support/crowd-
density/CrowdDensity-1....](http://www.gkstill.com/Support/crowd-
density/CrowdDensity-1.html)

I checked: about 20 per "row". To get the number of rows, figure out how long
the street is and then divide by 2 metres. That's roughly how many people
there are.

EDIT:

according to Wikipedia, Wiltshire Blvd is 25km long. I somehow don't think
there are that many people in the crowd

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tmaly
that's an extremely hard problem to solve.

I think doing an order of magnitude estimation would be your best bet.

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tictaktoe
lets just say there must not be enough to win Hillary the presidency!

