[Talk-GB] Aerial Photography

Peter Miller peter.miller at itoworld.com
Mon Sep 14 12:14:56 BST 2009


On 14 Sep 2009, at 11:57, John Robert Peterson wrote:

> Part of the idea of this project was to kick start thinking about  
> this sort of thing.
>
> The ideal situation for me would be if we could have some automated  
> tool on a sever somewhere receiving images from users, and  
> automatically rectifying them.
>
> This sounds imposable, but I believe that with a very small amount  
> of user help it could work:
> Images can be automatically pinned together in overlaps (and high  
> res images can be pinned onto wide area images) using tools similar  
> to those in Panorama Tools / hugin (this searches for notable points  
> in the image data, and matches them between images);
> searching the images for road markings (and/or cars) and matching  
> these to the gps traces already uploaded would give a reliable  
> enough way to add real world control points;
> if a concept of altitude is added, automatic control points between  
> images appearing on top of skyscrapers would not be too damaging;
> approximate terrain relief for most of the planet is already known,  
> this can be tied into the above to help;
> manually adding control points would be done by displaying already  
> rectified images next to a map, with the user adding pins to useful  
> points;
> images with no rectification data at all would be added using a push  
> pin system similar to that used on http://warper.geothings.net/
>
> the above is a pipe dream at the moment, but has the potential to  
> revolutionise how we do things in my opinion.
>
> Any further ideas on this?
>
> The images of stratford were taken mostly angled, with a few almost  
> vertical. we spiraled around the town and I took images out the  
> downward facing window, it seemed to work pretty well (if the  
> results are a little chaotic)
>
> mapping from these images is the million dollar question -- the raw  
> images are going up online at http://www.flickr.com/photos/thingomy/collections/72157622345143470/ 
>  and are fine for visual reference while mapping, but rectifying  
> them is a more tricky issue.

I get the impression that rectification gets a lot harder as the angle  
gets more slight and it is clear to me that a camera pointing straight  
down would be the most useful device going forward. The time of day is  
also important to avoid long shadows. I am pleased that this project  
is creating some useful discussion which we should continue to see  
what we can extract from these images and what we can learn going  
forward.

Tools to process images and to host rectified images seem to be pretty  
crucial to take full advantage of all this.

Fyi, I have added comments to some images to say what it is of, the  
bearing the image was taken at, and the appropriate link to OSM.



Regards,


Peter


>
> JR
>
>
> 2009/9/14 Tristan Thomas <tristan.thomas at wikinewsie.org>
>
> Many of the photos taken above Stratford upon Avon seem to be taken  
> at an angle-how do people find them for mapping from?
>
>
> 2009/9/14 Chris Hill <osm at raggedred.net>
>
> I used to hold a pilot's licence and I did some work photographing  
> archaeological sites.  Photos taken pointing sideways are much  
> harder to work with than photos pointing straight down. Any kind of  
> rectification adds unwanted artifacts.  I used to make high bank  
> angle turns (60' bank angle) over the feature I wanted to photograph  
> which made it very easy to photograph.
>
> I was trying to photograph a small area in detail, so circling over  
> the feature helped.  I was also using film (before widespread hi-res  
> digital), so there was a limited stock of film but the resulting  
> image was the equivalent of about 25mp.  To reduce parallax I used a  
> telephoto lens.
>
> It gives a very interesting overview, but it's not a patch on  
> surveying on the ground where you have access.
>
> Cheers, Chris
>
> Tristan Thomas wrote:
> I would be very interested to hear what people think of this  
> effort.  I'm currently studying to be a pilot & I know that many  
> people who do fly routinely take aerial pictures of the landscape  
> below, especially of towns etc.  I know most of them would be more  
> than happy to allow their photos to be used of OSM.  If we could  
> find a way to upload them somewhere, then I'm sure we could  
> dramatically increase the aerial photography we have without having  
> to pay to hire the planes or get it sponsored.  I could just upload  
> them all under one Flickr account for OSMers to look through & do  
> some tracing if they wish, but it doesn't seem the most efficient  
> way to do it?
>  Thoughts?
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