Grassroots mapping can be described as a low cost method of obtaining aerial photographs. As a carrier sensor it uses either a balloon filled with helium (if the wind speed is no more than 10 km/h) or kite flying (at higher wind speeds) (Grassrootsmapping.org, 2010). It could be argued that this is merely a variation on the UAV (Unmanned Aerial Vehicles), however, this approach is more useful for small community projects, mainly for its simplicity and low operating costs.
Difficulty: technologically demanding
Group size: small to medium – but at least two people to operate the camera carrier (balloon/kite)
Time required: Half day to full day (depending on the size of the area): Mapping takes at least one hour and photo editing takes at least two hours.
Links to other methods: This is mostly independent method. The result can be used as a basis for input Photo mapping.
The aim of this method is to collect aerial photographs of smaller areas and thus bring a completely new view to the studied area and to the community members. The collection and subsequent interpretation of the images is relatively simple and is a nice group work. Nevertheless preparation and knowledge of processes is essential.
History and Present
The idea of Grassroots mapping method is not new and the first attempts to mount the camera on a balloon or kite are dating back to the 19th century (Batut, 1890; Evans, 2002), but in the last few years it became popular again, mainly due to the work of Jeffrey Warren from MIT (Massachusetts Institute of Technology), who created the software needed to connect the individual images in a seamless picture (Warren, 2010). The whole product of his doctoral thesis, a methodology and software, was tested in community mapping in Lima, Peru, and also in accident of British Petroleum station (Grassrootsmapping.org, 2010b). Currently, there is number of community supporters of this method of collection and visualization of spatial information, sharing their experiences and failures at an open forum PublicLab.org.
The advantage of this method is the ability to obtain images of selected areas at very low cost. The disadvantage may be legal restrictions in various countries for acquisition of aerial photographs (limited air space and traffic, etc.). Another disadvantage can be relatively higher technical demands for the whole process of mapping and processing acquired images. Complete documentation for the various models and options is available on various open-source forums (DIY Drones, 2013; Public Lab, 2013).
In the Czech environment balloon mapping was used for example when mapping “selective” logging in Šumava National Park (Valůch, 2011), and the outcomes of the surveys were later used in a lawsuit that marked this as illegal felling (Hnutí Duha, 2014).
- Clearly define the scope of the area.
- Decide what device/carrier you would like to use – helium balloon or kite (according to weather conditions).
- Present the objectives of the project and the mapping method – explain why it is the most appropriate method chosen and how the results will be used further.
- Have enough time to photography.
- Process the picture using the example mapknitter.org.
- The resulting seamless picture can be presented to the community and server as a starting point for the group discussion.
Resources and tools
- Set for mapping
- Camera – ideally Canon, that can be easily reprogrammed using CHDK.
- PC connect to the Internet (mapknitter)
- Helium – if you decided for a helium balloon. To fill the balloon it is recommended to use two persons – especially for safety reasons.
- In the case of helium balloon calculate the necessary amount of helium – about 1 litre = 1 g of helium buoyancy – that is, if the camera weighs 150 g + 350 g of meteorological balloon, so it needed at least 500 to 600 litres of helium.
- As for the technical implementation of the entire mapping, so it is relatively simple. You need to have a camera (preferably Canon – because it enables reprogramming using CHDK scripts) and manually adjust its internal operating system so that it can continuously shoot e. g. every 2 seconds (CHDK Wikia, 2007).
- More is described in the article Trees, Chainsaws, Protest and Balloons (Valůch, 2011) or in the description of mapping the building of Faculty of Science UP Olomouc (Panek, 2014).
- Paper for notes.
This kind of documentation should certainly belong into the toolbox of organizations and groups that sought to expose the injustice and bureaucratic despotism. The greatest potential lies in the possibility to retrieve visual documentation that is not otherwise available. Finally, it is interesting and fun activity for a group of people that pushes traditional activism to the next level.
Examples experiences, literature, etc..
Aber, J. P., Aber, S. W., & Pavri, F. (2002). Unmanned small format aerial photography from kites for acquiring large-scale, high-resolution, MultiView-angle imagery. International Archives of Photogrammetry Remote Sensing and Spatial Information Sciences, 34 (1), 1 to 6
Aber J. S. Marzolff, I., & Ries, J. (2010). Small-Format Aerial Photography: Principles, Techniques and Applications (p. 268). Elsevier.
Batut, A. (1890). La Photographie aérienne par cerf-volant. Paris: Gauthier-Villars et fils.
DIY Drones. (2013). DIY Drones.
Evans, C. M. (2002). The War of the Aeronauts: A History of Ballooning During the Civil War (p. 358). Stackpole Books.
Grassrootsmapping.org. (2010a). An Illustrated Guideto Grassroots Mapping with Balloons and Kites.
Grassrootsmapping.org. (2010b). Gulf Oil Spill Mapping.
Hnutí Duha. (2014). Přelomový soudní rozsudek: Občanská blokáda nezákonného kácení na Šumavě byla oprávněnou poslední možností, jak zabránit úřední zvůli. Retrieved June 09, 2014
CHDK wiki. (2007). UBASIC / Scripts: A SimpleIntervalometer. Retrieved June 10, 2014.
Panek, J. (2014). Public Lab: Balloon Mapping at Faculty of Science, Olomouc, Czech Republic. Retrieved July 01, 2014.
Public Lab. (2013). Public Lab: DIY and environmental science community.
Valůch, J. (2011). Trees, Chainsaws, Protest and Balloons.
Warren, J. Y. (2010). Grassroots Mapping: tools for participatory and activist cartography. Massachusetts Institute of Technology. Massachusetts Institute of Technology.