Zanzibar Building Import
Zanzibar Building Import describes the import of approximately 360,000 building footprints of Unguja Island, the largest island of the Zanzibar Archipelago in the United Republic of Tanzania. This data was made available for import into OpenStreetMap by the Zanzibar Commission for Lands.
Source
The Commission for Lands Zanzibar is the source of this data. The footprints were derived from geo-referenced UAV imagery. Buildings were digitized at a 1:250 scale using the WGS84/UTM 37S (EPSG: 32737).
License
The Commission for Lands released the data under the Creative Commons – Attribution 4.0 International (CC by 4.0) licence. This licence is adopted from the UAV imagery from which the building outlines were captured and it gives users freedom to share and adapt the data with appropriate credit given to the Zanzibar Mapping Initiative and the Revolutionary Government of Zanzibar – Commission for Lands.
Attribution
The following attribute will be applied to the import changesets:
source=Commission for Lands - Revolutionary Government of Zanzibar
Data Quality
The original dataset has been checked for overlapping geometries, invalid geometries and attribute errors. Unique Building Identifiers and other attributes available in the original dataset will be omitted from the imported dataset.
Data Conflation
Some areas of the island already have existing OSM buildings. During the import process, existing geometry will be checked against high resolution drone imagery and if it is of poor quality as compared to the original dataset, it will be replaced. However, the entire history of the replaced geometry including the OSM ID will be retained.
Pre-processing
The original dataset is in shapefile format and will be converted into OSM format using ogr2osm. Building footprints are the only feature imported therefore, all new buildings will be tagged with the building=yes tag. Tags on buildings with updated geometries will be retained.
Work Plan
Due to the large number of buildings, considerable time will be spent on reviewing and importing the them. The import will be broken down into various zones using the OSM Tasking Manager which will enable multiple contributors to undertake the import tasks. The following contributor account will be used to manage the import.
- simoa (French)
- ibrahim8802
- Paolo35 (French)
- Mohd Kassim
- Asha Hashir
- Abdu Abdulla
- BASTILLE (French)
- Arafa Salim Hamad
- Add others!!
Import process
Import process will be done using JOSM and OSM Tasking Manager to manage the import process. Below is the recommended workflow for the task:
- On OSM Tasking Manager, select and open a task square in JOSM. Load imagery layer (Load UAV image from OpenAerialMap).
- Download existing OSM data from server.
- Load buildings data for your square
- Merge the buildings to the existing OSM data layer
- Run JOSM validation on the merged layer to identify and fix errors like overlaps, building in building, missing tags. Use the utilsplugin2 tools to manage conflation, geometries and preserve tag histories for existing buildings.
- Run a final validation to fix any highway/building related warnings.
- Upload all changes.