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January 04 2012


Public Lab Produces Wetlands Maps From Balloon and Kite Flights

The Public Laboratory for Open Technology and Science (PLOTS) is an organization and membership community which develops and applies open-source tools to environmental exploration and investigation. Public Laboratory's mapping tools, openly available and easy to use, are putting the ability to do processes such as georectifying in the hands of people who may have never created a map. 

Using aerial mapping techniques, residents and volunteers of the Gulf Coast region began field mapping trips in 2010 to document the impact of the BP oil spill. Between May 2010 and April 2011, tens of thousands of images were collected and 50 regional maps created. Between May and October 2011, Public Laboratory partnered with Dr. Alex Kolker, from the Louisiana Universities Marine Consortium to begin a bi-monthly monitoring of select oil impacted and non-impacted sites in the Barataria Bay region. The intent of this phase of wetlands mapping was to monitor change over time with high-resolution aerial and ground imagery.

Wilkinson Bay in Louisiana.

The fieldwork that goes into collecting images is the first step in creating maps. On the back end, the next step involves georectification -- the process where balloon and kite aerial images are "published" into geographic data. Simply, it is the alignment of an aerial image with a map or other spatial data of the same area. This part of the process is where images become maps and are associated with geographic standardized formats so that other users and programs can exchange and experience them in the same context.

Public Laboratory map production has used some specific techniques in creating wetlands maps. The maps are made through a georectification process by which adjacent images from the flights are merged in overlay as they are aligned to existing mapping information. Different "base" data can be used in these types of projects. In this case, we're georectifying the imagery through examination of the new images with existing imagery.


A new unaligned image (right) about to be georectified with the other imagery. The base layer is visible in the background.

Distortion correction is applied to the new images, and they're moved around so that the same features of the base map are in perfect overlay with the new image on top. In the bayou setting where lots of change is occurring on the outer coastlines, features such as vegetation composition and interior waterways are used to match each overlay. Although waterways in marshland may shift quite rapidly, the center of a 3-way intersection is quite stable, as a rule.

Matching the imagery based on the interior features has proven effective in this simple map-making technique. While the outer coastline in our new images has changed since the time of the base data, the process of fitting the imagery with all of the interior ground control features allows us to discover where the coastline is with some measure of confidence. Or to put it differently -- when the alignment happens with the historic data in most of the image, then the new areas can be extrapolated with regularity.


The image is aligned in overlay with the base data during the georectify process.

Visit the Public Lab site for guides and discussion about the process and to view image sets and maps that have already been published in the map archive. The archive is a home and distribution channel for published open-source maps.

Visit MapKnitter.org to learn about our map-stitching tools and to view maps that are being created by people who are using aerial mapping techniques in new ways to document and monitor sites and events that are of importance to their community.

April 20 2010


Helium Baloons with Digital Cameras Create Grassroots Maps


I'm getting ready for day five of a two-week workshop for high schoolers at Beaver Country Day School in a suburb of Boston. The subject is my project, Grassroots Mapping, which helps teach people -- often young people -- around the world how to be activist cartographers and how to make their own maps. There's a twist, however: Instead of just marking a Google Map, or walking around with a GPS tracker, we construct simple capsules to hold a cheap digital camera, and send the whole package up on a helium balloon or a kite. The images are then stitched, geo-referenced, and published, as in the following picture:


This isn't exactly your typical high school activity. My workshop at Beaver Country Day School is part of a series of studio design-style courses that make up the NuVu Studio -- an experimental education project where the students get hands-on exposure to topics like alternative energy and "the future of labor."

It differs quite a bit from other workshops I've taught in places like Amman, Jordan and Lima, Peru, in that the idea of "subjective geography" seems somewhat less immediate. I didn't have to explain to anyone in the West Bank, for example, that mapping is not a neutral act, or that it's a social construction with a profound political meaning and agenda. But here in Walnut Hill that seems a bit distant...


Mapping a Tea Party

I did show the students maps I'd made in urban slums in Lima, Peru, and it's not that they were uninterested in the iniquities of urban slums. I'm really facing the same issue as I did in Peru: Before this kind of work (or play) seems exciting and relevant, it has to come with a sense of ownership. Unless we can find a way to situate do-it-yourself mapping, it's not going to resonate.

In Peru, the need for maps to establish land claims was obvious. Unlike here in Boston, my collaborators there had built their homes and community brick by brick with their own hands. They'd made their own geography, so mapping it was just another step.

I suggested to students that we go to a Tea Party rally where a protest against Sarah Palin's keynote speech was occurring. There would be plenty of political context there, I thought. The students were excited (even at the -- distant -- prospect of getting arrested). But our satellite building session overflowed into the afternoon, and when the rally ended we were still in the same room, covered in styrofoam bits and duct tape. Some violent "flight tests" assured that our new camera enclosures were ready for takeoff:

In any case, it's still just plain fun to fly balloons, and this week the students will choose a site to map and explain their reasoning. The hope is that this two-week course will form the basis for an international map-making competition -- a kind of student X Prize, which we're beginning to call the One Satellite Per Child project. Participants will prototype a mapping rig just like we're doing here at Beaver Country Day, collaborate with other students from around the world through a website, and win awards for lowest weight, best documentation, best application of mapping, and other goals.


Why Grassroots Maps?

Grassroots mapping provides an exciting context for situated learning, including subject material from history, geography, physics, politics, and even chemistry. As an example, when we were trying to lower the cost-per-flight, we used stoichiometry to find out how many aluminum soda cans we had to mix with lye to produce enough hydrogen to fill a 5-foot balloon. (Answers varied from 15 to 33.8 cans -- we'll have to try it to find out who was right.)

This is the dream-stuff of many educators, and indeed we often have more interest from Beaver Country Day's teachers than their play-it-cool high school seniors. I've been asked several times whether teachers can take the course, and perhaps that's more important anyways, given that it may represent an opportunity to influence how education works.

Soon we'll start to tackle some advanced projects, like a camera-carrying remote controlled airplane, and an inflatable kite filled with helium. Stay up to date on our progress at the Grassroots Mapping blog.


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