The View from Above

Over the last few months I’ve been involved in three different aerial imagery projects, all of which were to make imagery available for OpenStreetMap contributors. It’s nice that we have imagery available from the guys at Yahoo!, but on occasion we lay our hands on some better stuff.

First off was Stratford-upon-Avon, here in the UK. As an experiment we hired a small plane, put one of our contributors on board with his SLR, and flew around town. All the photos were then put on line, and even though I’d never been to the place before I could use Tim Water’s online map rectifier and re-purpose it slightly to warp the photos and line them up to the map data. Other people did the same, and then I collected all the separate images and processed them into one map layer. A few days later I was at a “Traditional GIS” conference in Stratford, and there was a great deal of interest from people in the aerial imagery project and OSM in general. I can recommend it as a publicity stunt for other conferences!

Central Stratford

You can see more pictures of the end results on flickr, or read more about it on the OpenStreetMap wiki.

Next up was the Philippines. After massive deadly flooding aid agencies on the ground were using OpenStreetMap to help with the disaster relief. Manning Sambale from the OSM Philippines community received a donation of satellite imagery of part of the affected area, and asked for help processing it and making it available. I made some space available for him to upload it, and then processed it into the right format for OSM editors. With such high-quality imagery available so soon after the disaster, OSM volunteers both in-country and working remotely set about mapping the villages and marking on the locations of bridges and damaged areas. You can get a sense of scale of the damage from the image below – the gravel banks covered fields and villages around the river, and the imagery was a huge help.

Philippines imagery

The third project was in Georgia, USA, where I got hold of some fairly recent (2007) imagery from the Department of Agriculture National Aerial Imagery Program (NAIP). Although Yahoo! has good quality imagery available across the whole of the USA, this public-domain imagery was more up to date and slightly higher quality that what Yahoo! has in rural areas of Georgia. This is by far the biggest set of imagery I’ve had access to – hundreds of gigabytes of the stuff – and only a handful of counties were processed.

Georgia Imagery

I’m sure as time goes on we’ll get more and more sources of imagery to help with OSM, and I look forward to lots of “crowd sourcing” experiments like the stuff from Stratford as much as I like the imagery from the professionals.

If you have access to any sources of imagery and need a hand getting it processed, get in touch!

6 thoughts on “The View from Above

  1. Peter Miller

    Thanks for championing this imagery stuff Andy; I have felt for some time that this is a hugely important resource and one that we have until recently under-utilised. It great to see it being talked about.

    Do remember that the Gaza Strip map is now looking great based on photography flown after the Jan 2009 conflict and also an impressive ground survey.

    The West Midlands in the UK is now gearing up to buy aerial photography for the whole urban area and if other people are missing photography for their part of the world then do think about either buying satellite photography (not that expensive actually) or flying your own. There is a wiki page with further details and a place to put details of your appeal for funding.

  2. maning

    Again, I thank you Andy for helping us setup the imagery in Pangisanan, Philippines. What used to be a blank slate 1.5 months ago now looks better:

    http://www.openstreetmap.org/?minlon=120.331&minlat=15.9464&maxlon=120.602&maxlat=16.2202&box=yes

    More work is needed but we had excellent progress already.

    Another thing I realized for implementing webmapping for disaster related event is there maybe disruptions in electricity and internet connection in the area. So it is good to have offsite webservers rather than hosting the service here.

  3. Steve

    Hey
    I’m having trouble using my geothings warped images in potlatch. How do you do it? I can edit them in JOSM using the WMS plugin, but can’t find a similar option in potlatch.

    Thanks
    Steve

  4. Robert Sund

    I know someone who flies a size 90 RC helicopter with camera, sometimes for pay, but usually just for fun. It may lift 3,5 kg of payload in sustained flight but a SLR and its gear suffice for most tasks. I own a Legend HCX and usually take a photo of the GPS screen to ensure that timestamps is accurate.

    What range in altitude is preferable for the aerial photography?
    Is a GPS to localice the images useful?

    If the altitude is within range I may ask if he is interested, and when he might donate some flying.

  5. Andy

    Steve, they need to be processed into standard tiles in order to work in Potlatch – it can’t do WMS directly. I just use the generate_tiles.py from the OSM SVN with geotiffs downloaded from http://warper.geothings.net

    Robert, the longer lens the better – say 100mm+ would be great – to get flat images with the least distortion. So if you fly low, you’ll get really really good images but only of a very small area. Give it a try though and see how you get on!

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