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Processing MapSwipe output for the HOT Tasking Manager

Posted by pjstewart1984 on 20 March 2017 in English (English)

Hello everyone,

MapSwipe - the mobile app that allows users to swiftly search through satellite imagery and identify huts, houses and villages - is accelerating the Missing Maps mapping process. Its output shapefiles, comprising only tasks identified as containing huts, houses, or villages, allow Missing Map's task creators to omit from projects any tasks without huts, houses and villages. In short, any tasks that do not require mapping.

However, some areas covered by MapSwipe output tasks are quite likely to have already been mapped in OpenStreetMap. A little processing of MapSwipe's output shapefile can make it even more effective!

First, MapSwipe output can be downloaded at http://mapswipe.geog.uni-heidelberg.de/download/ or using the MapSwipe Tools which can be downloaded at https://gitlab.com/giscience/MapSwipeTools/tree/master.

Using overpass turbo:

1.1. Download the area's building=yes and landuse=residential GeoJOSN files (Wizard > build and run query, then Export > as goeJOSN). The building data usually take a little while to download.

Using QGIS:

2.1 Convert the GeoJOSN files into shapefiles (Layer > Save As...).

2.2. Merge the two shapefiles (Vector > Data Management Tools > Merge Shapefiles to One...).

2.3. Clip the merge shapefile to the MapSwipe output (Vector > Geoprocessing Tools > Clip...).

2.4. Select MapSwipe tasks with the merge shapefile within their boundaries (Vector > Research Tools > Select by Location...).

2.5. Export selected tasks as a shapefile (Layer > Save As...).

2.6. Invert step 2.4's selection (right-click on layer > Open Attribute Table > Invert selection).

2.7. Export selected tasks as a shapefile (Layer > Save As...).

The shapefile created in step 2.7 will partly dictate the HOT Tasking Manager project. Further processing of the shapefile created in step 2.5 is required.

Using QGIS:

3.1. Clip the landuse=residential shapefile to the shapefile created in step 2.5 (Vector > Geoprocessing Tools > Clip...).

3.2. Select the clipped landuse=residential shapefile's residential areas with the building=yes shapefile within their boundaries (Vector > Research Tools > Select by Location...).

3.3. Invert step 3.2's selection (right-click on layer > Open Attribute Table > Invert selection).

3.4. Export selected residential areas as a shapefile (Layer > Save As...).

3.5. Select the shapefile created in step 2.5's tasks with the shapefile created in step 3.4's residential areas within them (Vector > Research Tools > Select by Location...).

3.6. Export the shapefile created in step 2.5's selected tasks as a shapefile (Layer > Save As...).

Finally, using QGIS:

4.1. Merge the shapefiles created in step 2.7 and 3.6 (Vector > Data Management Tools > Merge Shapefiles to One...).

4.2. Convert the shapefile created in step 4.1 into a GeoJOSN file (Layer > Save As...).

The GeoJOSN file created in step 4.2 is what is used to create a more streamlined HOT Tasking Manager project. In brief, it constitutes MapSwipe's output minus tasks already mapped but including residential areas without buildings within them.

Thanks for reading,

Paul

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