Freetown drone mapping

Overview

Freetown faces significant urban challenges, including weak enforcement of municipal regulations, poor waste management, limited emergency response, and difficulties in climate adaptation. A major obstacle is the unclear delineation of communities, which complicates governance and resource distribution. The city also struggles with access to essential services such as clean water, sanitation, power, transport, and security, hindering equitable development.

To address these issues, the city plans to use high-resolution imagery, a Digital Elevation Model, and 3D Mesh products to improve urban planning and ordinance implementation. These tools will enable precise mapping of Freetown’s 83 km², aiding zoning, infrastructure planning, and efficient service delivery. Pathway accessibility will also be assessed, with emphasis on inclusivity for people with disabilities.

The project involves comprehensive drone mapping of the city. It is funded by GIZ and led by Freetown City Council, with contributions from national and local stakeholders. Key partners include the Ministry of Lands Housing and Country Planning, the Office of National Security, the Civil Aviation Authority, and the National Commission for Persons with Disabilities. Civil society groups such as CODOHSAPA, FEDURP, and OSM Sierra Leone also contribute, alongside local residents, to ensure the project meets community needs.

Training

Because of limited time, the technical and project management team decided to use an “on-the-job” training approach, wherein, potential participants were introduced to drone piloting and image processing on the first 2 days and their progress was measured based on their improvements and willingness to learn. The selected pilots and data processors were continuously trained to manually and automatically maneuver flights using the drone tasking manager and troubleshoot technical issues with the drone through the course of the project.

Drone mapping

Upon acquiring the necessary licensing and registration of drones and permits to fly, 5 teams consisting of 2 mappers and 3 data processors embarked on drone image collection throughout Freetown, Western Urban. The entire city was segmented into 5 mapping blocks; Aberdeen_Murraytown_Wilberforce, Congocross_Wiberforce-Hillstation, NewEngland_Kingtom, Saniabacha_Welligton and Wellington_Jui. Pilots simultaneously chose plots of varying areas and collected drone images within them.

Pilots were provided with power bars, transportation stipend, reflector vests and drones. We started the activities with the Mayor of Freetown executing the first flights.

High Resolution imagery

After uploading the drone images to the S3 database, they were extracted by the photogrammetry team and they developed a methodology to process the images into one large orthomosaic and other digital models. The team requested for additional images and rerun of existing ones that needed modification. A bulk of the imageries have been uploaded to OpenAerialMap for public use while adhering to local regulation to blur out sensitive areas across the entire area of interest.

Data use cases

Two OSM-Sierra Leone volunteers, Sia Kamanda and Stephen Kassigbie, were trained by Peter Masters to map movement barriers affecting persons with disabilities in informal settlements using ODK and Mapillary. The two-day exercise informed the development of a robust methodology for field data collection in Cockle Bay, Kolleh Town, and Coconut Farm. The collected data was analyzed to identify barriers faced by disabled people and to determine optimal routes or exit points during emergencies.

The team engaged the National Commission for Persons with Disability to discuss how the work could support the commission’s mandate. A follow-up meeting was held at Freetown City Council, where the outcomes of the disability mapping were presented, and the potential for further analysis to improve data usability was highlighted.

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