

Webapp: image recognition to find nearest tennis courts from satellite photos - Torn
http://ahathereitis.blogspot.com/2009/12/how-it-works.html

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aantix
Specialized image recognition especially detecting objects with fairly rigid
structures or common color patterns seems like a nice intermediary step
relative to the more complex issue of detecting arbitrary objects.

During a few drunken nights my friends and I have had many conversations about
doing an image crawler that would detect nipples.

You know that bathing suit that's see through that your friend's hot
girlfriend likes to wear and posted a photo of herself on MySpace (just to be
a tease)? Yeah, we wanted to find those photos.

We were going to call the site tittr.com.

Turns out nipple detection has many practical applications especially in
digital mammography and there's even been a few research papers written on the
subject.

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lmkg
There's actually existing vision recognition software that can identify a blow
job, and blur out the relevant part of the pictures. Such software is
marketable, although I think it was an academic paper. I'm not going to look
for a link at work, but I do remember it was robust with respect to rotation
of the picture, which made for some amusing collages.

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eob
Impressive site. Looking at that was one of those "DOH! Why didn't I think of
that!" moments, which is usually the indicator that you've got a good idea :)

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Torn
In action over at: <http://www.ahathereitis.com/>

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tome
I had trouble reading this URL. At first I thought it was "a hat here it is"!

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judofyr
I had really trouble reading this URL after you mentioned it looked like "a
hat here it is".

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pierrefar
That's impressive.

It seems to be missing a few. All the examples I've seen missed are actually
single courts (like in the backyard of a house). To see the examples, go to
Palo Alto/5 miles and look just to the west of Sharon Heights golf club, near
the Valley Rd, Walsh Rd, Sargent Ln, Moore Rd area. I can count 9 single
courts that are not labeled.

EDIT: Looking closer, these 9 could be just outside the 5 mile radius of the
search.

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Maciek416
This is awesome. I'd like to see more about the overall structure of the
program, i.e. how the search work was partitioned and completed.

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axiom
Old school technique. He should have just used SIFT keypoints or something.
Much faster and more accurate.

Still, cool demo.

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sga
It seems a license from UBC would be required to use the SIFT algorithm in a
commercial venture. This may have been enough to dissuade the algorithms use
in this case.

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sga
OP mentions this being a "hobby project" so my comment re. why the SIFT
algorithm was not chosen is likely incorrect.

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xipetotec
The main reason is that I haven't read up to that section of "Learning OpenCV"
book... I guess I have some additions to my reading list ;)

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NathanKP
Too bad it isn't real time and able to find tennis courts anywhere that Google
Maps has coverage. I guess, however, that all that image recognition is highly
CPU intensive and thus he has to generate results for an area, cache them, and
then deliver them.

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xipetotec
The biggest problem is that I don't think Google would allow me to do that -
from what I understood from their Maps TOS, the imagery is strictly for
displaying to the visitor.

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NathanKP
I'm sure that if you sent them an email telling them what you were doing they
would allow it. (Either that or they would say "Hey! Good Idea!" and a few
months later they would come out with Google Sports Courts, able to find
basketball courts, tennis courts, football and soccer fields, etc.)

It would be worth a try at the very least.

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gcheong
Now if only there was a way to do this in real time for street parking.

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Torn
I'm wondering what sort of spatial / geo-enabled database and backend he's
running with. GeoDjango with PostGIS and some cronned script to do crawl
google maps and do the computer vision stuff for a given area would be what
I'd use. He could even go the whole hog and EC2 it, spinning up instances as
needed and prioritising the crawling of commonly-requested zip codes.

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xipetotec
He is here ;)

Alas, Google doesn't allow that - their satellite imagery are for displaying
purposes only... I guess it can be argued that storing the imagery, processing
it, and discarding after processing is not a violation of TOS, but it is
likely that retaining the coordinates of the found objects is a "derivative
work", which is prohibited, yadayada.

So I just get public domain imagery from USGS. It is slow, but public domain.

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bockris
I'm quite intrigued by this but it didn't find the tennis courts near my
house. I think it was foiled by tree's and shade blocking some of the lines.

Edit: oops. I didn't read the disclaimer about only processing the Bay Area
for now.

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mumrah
Didn't pick any courts up in my city (and there are plenty). Here's one right
near my house <http://i49.tinypic.com/8yi4cm.jpg>. Maybe the search hasn't
processed my area?

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onewland
Is your city in the Bay Area? He specifies it's only processing the SF Bay
Area.

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onewland
I'm really impressed by this. Good job.

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pclark
amazing

