In some regions of the world, the relationship with the environment is troublesome, as it can give both access to natural resources and exposure to diseases. A problem of this kind is happening in Senegal, in the region of Saint-Louis, which is endemic for schistosomiasis, the most devastating neglected tropical disease affecting Sub-Saharan Africa. Schistosomiasis has a water-based transmission cycle: the parasite driving it follows a complex life cycle in which snails, living on aquatic vegetation typically found in rivers, canals and swamps, act as intermediate hosts. When humans enter infected waters, the parasite can penetrate their skins and eventually settles in the urogenital or intestinal apparatus, causing long-lasting negative effects on human health and child development. In the Senegal River Valley, people living in rural places have no other choice but retrieve water and release wastewater using environmental sources, which put them at high risk of infection.
Figure 1 A view of water-points in the region, Ntiagar village
Mapping can be very helpful in this situation, as it allows to:
Locate villages in rural areas of the region to understand where vulnerable people live,
Identify snail habitats that may represent the most infectious spots.
With the aid of eco-epidemiological models, it is possible to assess the disease burden and design possible control policies. Some attempts to describe schistosomiasis transmission at either continental or country scales have already been made by the scientific community. The key question is whether it is possible to inform such models at finer geographical scales by using OSM data and multispectral satellite imagery.
This problem has been subject of studies at Politecnico di Milano within the MASTR-SLS Polisocial research project , led by Prof. Renato Casagrandi. The 2018 YouthMappers Research Fellowship made possible great advances in this research line, as it brought a dynamic component to the project, letting YouthMappers students visit and work in the focal areas and co-operate with other young leaders.
In particular, after the Research Fellowship Workshop in June 2018, the YouthMappers leadership provided us with the contact of the YouthMappers chapter at Université Gaston Berger in Saint-Louis, Senegal. This contact started a fruitful collaboration between the two chapters, so that it has been possible to organize, in November 2018, a cross-continental mapathon. During the event, a remote connection between three different organizations was established: PoliMappers at Politecnico di Milano (Italy, guided by Michael Montani and Dr. Lorenzo Mari), UGB YouthMappers at Université Gaston Berger in Saint-Louis (guided by Prof. Renato Casagrandi and Fabio Cattaneo, the current Polimappers treasurer, who traveled to Senegal for the mapathon) and students from the African Institute for Mathematical Sciences at ‘Mbour (Senegal, led by Dr. Amadou Lamine Toure, postdoc in the Ecology Group at DEIB, Politecnico di Milano, within the MASTR-SLS project). The event has been broadcasted in real time, reaching an overall worldwide contribution of 150 OpenStreetMap users participating to the mapathon.
Organizing such an event hasn’t been easy at all: several technical aspects had to be decided in advance and unexpected issues emerged during the event – like discontinuity in web connections. However, the mapathon has been so successful that good results on the TeachOSM project were registered. Even more importantly, the interest stirred by the event pushed some passionate Senegalese students to create an OSM mapping group in Richard Toll, Saint-Louis, Senegal.
Everyone can still contribute to this project on teachosm.org by mapping villages and buildings in the Saint-Louis region!
Figure 2 Snapshots of the cross-continental mapathon event in November. Left: Michael Montani and
Dr. Lorenzo Mari at Politecnico di Milano (Italy) with Polimappers and students. center: Fabio Cattaneo and Prof. Renato Casagrandi at Université Gaston Berger (Saint-Louis, Senegal). Right: Dr. Lamine Toure with students at the African Institute for Mathematical Sciences at ‘Mbour (Senegal).
In March, I traveled to the Saint-Louis region with Fabio and Lamine to conduct some fieldwork aimed at providing ground-truthing for remote detection of aquatic vegetation. Indeed, in order to train an algorithm to see from satellite imagery where the potential habitat of the snails is, a closer (multispectral) look has to be taken directly from the field… with drones!
During the permanence in Senegal, we had the possibility to make surveys on spots of particular types of aquatic vegetation composing the habitat of the snails. For these surveys, we were joined by Ibrahima Diallo, the president of the UGB chapter of Youthmappers who was so instrumental also for the organization of our mapathon in November 2018.
Figure 3 The multispectral mapping team moving from waterpoint to waterpoint, Ndiawdoun village
Even in this case, the job has been tough. In addition to the predictable complications of fieldwork, we faced many practical issues that don’t usually show up during planning. Gardening reed to recover a fallen drone, towing our pick-up truck stuck in the mud with a broken wheel, and being on the lookout for hungry falcons are examples of such issues.
In the end, several good samples of spectral signatures have been retrieved from the aquatic vegetation at different sites, most of the times meeting people living in nearby villages who were curious about our activities. This has definitely been one of the most exciting aspect of our fieldwork, in particular when we had the possibility to interact with kids living there. They were astonished when looking at the drone, screaming at it and wanting so much to touch it!
Figure 4 A falcon comes to inspect the alien bird smoothly flying over the aquatic vegetation
Université Gaston Berger (Left) and Ndiawdoun village (Right)
Our journey to Senegal has ended with a meeting with UGB YouthMappers, who took us to visit their university and told us about their activities. This group is so passionate about mapping that they were eager to learn how to use the drone! Of course, we used it also to take some selfies: what about this one?
Michael Montani has a BS in Environmental Engineering and is MSc student in Geoinformatics Engineering at Politecnico di Milano, Italy. He is president and co-founder of PoliMappers, the first European chapter of YouthMappers. He is one of the 2018 YouthMappers Research Fellows, mentored by Prof. Renato Casagrandi, with a research project focused on the production of schistosomiasis risk maps, through OSM data and multispectral satellite imagery, as proxy for an eco-epidemiological model. He is a geek with the desire to apply geospatial data analysis and machine learning to humanitarian purposes.