Grassroots Mapping in Palestine

Grassroots Mapping in Palestine

Josh Levinger and I visited the West Bank for a few days following the MobileActive/UNICEF Mobile Data Innovations workshop. (Andrew posted about this last week) We were hoping to meet up with some members of the activist community who are organizing against the growth of Israeli settlements into Palestinian land. As mappers, we hoped to test some new low-cost tools and to learn about how such techniques can support communities in this fundamentally geographic dispute.

We met up with some Palestinians and volunteers who were planting trees in Umm Salamuna (view in Google Maps) on a hillside which is scheduled to be annexed by a nearby Israeli settlement, and converted into a graveyard. The planting was organized by Alice Gray of Bustan Qaraaqa, so that if the land is taken over, the trees would have to be uprooted or chopped down before the land can be used.. As I understand it, one of the means by which settlements claim land is by using an Israeli law which opens land to new settlement if it has lain fallow for more than three years -- so planting the hillside may defend it from such a claim.

The wind was so strong that our first kite, carefully made that morning from dowels and Tyvek, shattered immediately. Instead, we launched a small soft kite with an iPod nano attached to it. Here's a stitched image of the video footage we captured:

See all the pictures on Flickr.

The iPod has an SD camera which can capture many hours of video - and it's so super light that we can fly it on a pocket kite. Many of the frames are blurred and the resolution is pretty poor (we'd thought of using a Flip camera but they're more expensive and heavier) but when you go through the footage frame by frame you can find lots of good images. We then stitched these together with Calico and got the above image. It helped a lot to put a small 'sail' on the back of the iPod so it didn't spin as much.

Everyone was cold but once we started flying the kites we all got really excited. The owner of the land was there with his kids and they helped assemble the rig and fly the kite:

kite-flying-2

The mapping was a big success - everyone 'got' why we were doing it, that documenting the tree planting and how they're changing the landscape is a form of testimony. We're still working to rectify the imagery, and I'd like to ask folks if they have any ideas - the stitching software we're using assumes images were taken from a single viewpoint, but the kite and camera were moving all over the place. As you can see above, the stitching distorts things and we lose a lot of detail - how can we reconstruct a high-res image that assumes multiple perspectives? I'm looking at this tutorial to start with. We're also thinking about an algorithm to dump the clear, undistorted and unblurred frames from a movie file. Ideas?

We'll be adding this material to the Grassroots Mapping wiki, where we're putting together a comprehensive guide on low-cost participatory mapping techniques. Our hope is that we can offer a Grassroots Mapping Kit which people can use to reproduce these techniques to explore and document their own geographies no matter where they are.

Reblogged from Unterbahn.com

Comments

Hi Jeffrey.

I'm in mapping as a job and another way to stitch mapping together is to use a common, ubiquitous photo editing package. One commercial one comes with the ability to convert the "dumb" (ie non-geo co-ordinated) image into a Geo-Tiff.

However, once the images are stitched into one larger image, then it should be geo-referrenced, ie selected pixels / images (depending on the accuracy required) matched 100% positively to features on the ground which have a known position (GPS co-ordinate is fine, again, accuracy dependant). The amount varies upon the size of the area and the accuracy required, but an even spread is clearly best, and the more points the better for accurate representation over the entire image. Again, this is done with mapping-type software, which then "undistorts" (or "re-distorts") the image to fit the ground.

The photos we normally use have a 30% top to bottom, 60% lateral overlap to help with removal of distortion / shadow as well as more points to stitch, which again reduces accuracy error.

The important "baseline" reading is the co-ordinates of where the photographs were taken. This can be done using the GPS co-ordinates from the phone, decent guesstimate of balloon height and direction / distance above the ground co-ordinates, then pythagorus to determine camera location when the photos were taken.

I hope this is of assistance to you guys!

Any more information or help, then please don't hesitate to contact me via leepants12@hotmail.com and I shall then, if required, provide other means of communication if you need to contact me directly.

Thanks!

Lee