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Four-County Digitization

The OpenStreetMap Digitization project was geared towards updating OpenStreetMap with up-to-date data to assist the Liberia Household Social Registry Data Collection Project across four counties (Bomi, Bong, Maryland and Nimba) in Liberia. iLab in partnership with Humanitarian OpenStreetMap Team (HOT) was required to successfully digitize all roads and buildings across the four counties containing approximately 220,000 buildings and several road.


To begin with, we assessed the current state of OSM in Bomi, Bong, Maryland, and Nimba counties. This assessment was conducted by combining HOT’s Export Tool and OSMAnalytics in combination with QGIS and JOSM. Through this process, the project team was able to assess by county:

  • Number of buildings

  • Number of buildings with attribute details (purpose, roof material, etc.)

  • OSM Completeness (OpenStreetMap buildings compared to data of built-up areas from "Global Human Settlement Layer")

  • Kilometers of roads

  • Kilometers of roads with attribute details (highway type, condition, etc.)

  • Connectivity of road network in OSM

  • Data quality analysis using the JOSM Validation Tool and Osmose

Additionally, we assessed the recency, availability, and quality of imagery sources for the extent of the four counties. After assessing Microsoft Bing, MAXAR (formerly DigitalGlobe Premium and Standard), Mapbox Satellite, and ESRI World Imagery, we resolved on the MAXAR due to its clarity and recency.

All four counties, Bomi, Bong, Maryland, and Nimba, had a population of 1,016,030 as of the 2008 National Census. In OpenStreetMap (OSM), 161,440 buildings have been mapped prior to the digitization project of 2019. Comparing these datasets, the project estimated that there will be a maximum coverage ranging from 300,000-400,000 buildings following digitization.  Additionally, 11,728.2 km of roads have been mapped in OSM for all counties. 

Existing building coverage in OSM ranges from low to moderate in comparison to built-up area data, with the exception of Maryland County which has a high estimated coverage. Data quality analysis of all counties showed existing building and road network geometry issues that were addressed during digitization to improve overall data quality. 

During project implementation, 15 Digitizers were recruited plus iLab’s team of Supervisors successfully digitized and validated all roads and buildings across the four counties. A total of 222,996 buildings (215,855 added and 7,141 modified) were successfully digitized excluding the ones done by the Supervisors and the HOT Indonesian Team of Validators. 


Considering this was a participatory mapping project, the project hosted a mapathon to grow and building the capacity of the local mapping community.

“Monrovia Mapathon 2019” as it was duped had 61 participants. Participants created OSM accounts and were trained on how to work in OpenStreetMap, JOSM, Tasking Manager and other tools before engaging the main mapping activity for the day which was to digitized the city of Fish Town in River Gee County. Because several of the participants were new to the network of mappers, we mapathon was only able to successfully digitized 42% of the city.

The project was able to successfully get all four counties fully on OSM, a data that could be used for variety of interventions from Education, Health, among others.

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