Welcome to Day 4 of our #30DayMapChallenge series! After mapping public datasets, today we share our own data—built from scratch through rigorous spatial analysis.
Today’s theme: My Data
AT A GLANCE:
- Proprietary dataset created from scratch through spatial analysis of engineering plans
- 2,553 buildings identified within the 90-meter right-of-way
- 700km corridor analyzed across Lagos to Cross River State
- 946 PMTiles generated for web delivery of our building footprint data
Reading time: 4 minutes | Map Challenge Day: 4 of 30 | Theme: My Data
The Map: Our Data, Your Transparency
This map visualizes a dataset we built from the ground up—transforming fragmented government engineering plans into accessible, actionable information. Every building polygon represents hours of careful digitization and spatial analysis.
Lagos-Calabar Coastal Highway
Map Layers & Legend
Zoom to 12+ for buildings • Satellite basemap
Impact
Buildings
km Length
m ROW
States
Data Source: Lagos-Calabar Coastal Highway Engineering Plans
Analysis Method: Spatial overlay of buildings with 45m centerline buffer (90m total ROW)
Data Format: PMTiles vector and raster tiles for efficient web delivery
How to Explore This Map
- Zoom in to see individual buildings we’ve identified and digitized
- Click any building to see its position within our dataset (1 of 2,553)
- Zoom to level 11+ to overlay the original engineering plans we georeferenced
- Toggle layers to compare our analysis with source documents
Data note: Every building polygon was manually verified against high-resolution imagery and engineering drawings.
Why We Built This Dataset
The Data Gap:
When demolitions began for the Lagos-Calabar Coastal Highway, affected communities lacked access to clear, comprehensive information about which properties fell within the right-of-way. Government engineering plans existed but weren’t publicly accessible or spatially indexed.
Our Methodology:
- Georeferenced 16 engineering sheets from Federal Ministry of Works
- Digitized the entire 700km centerline with sub-meter accuracy
- Applied the 45m buffer per official specifications (90m total ROW)
- Identified 2,553 structures using high-resolution imagery analysis
- Generated 946 PMTiles for efficient web delivery
The Result: A freely accessible dataset enabling property owners to verify risk, communities to plan, and government to improve compensation processes. Data transparency serves accountability.
Why “My Data” Matters
Creating proprietary datasets fills critical information gaps in public infrastructure projects:
Accessibility: Government engineering plans often remain locked in PDF formats or physical archives. Converting them to web-accessible spatial data democratizes information.
Verification: Property owners can independently verify if their buildings fall within the right-of-way without relying on unofficial sources or rumors.
Accountability: Publicly available data creates a baseline for monitoring actual demolitions against official plans, enabling oversight.
Analysis-ready format: PMTiles and vector data enable researchers, civil society, and journalists to conduct independent analysis and reporting.
This dataset transforms opaque infrastructure planning into transparent, queryable information accessible to anyone with an internet connection.
Project Context
The Lagos-Calabar Coastal Highway represents one of Nigeria’s most ambitious infrastructure projects—700km connecting Lagos to Cross River State through 9 states. Our analysis focused on the officially-designated 90-meter right-of-way (45m each side of centerline).
Data Processing Workflow
Step 1: Georeferencing - Aligned 16 engineering sheets to real-world coordinates using ground control points and satellite imagery.
Step 2: Centerline Digitization - Traced the highway alignment across the full 700km corridor with sub-meter precision.
Step 3: Buffer Generation - Applied the 45m setback specification to create the impact zone polygon.
Step 4: Building Identification - Systematically identified all structures within the ROW using high-resolution imagery and engineering plans.
Step 5: Web Optimization - Converted vector data to PMTiles format, generating 946 tiles optimized for zoom levels 10-18.
Result: A dataset containing 2,553 building footprints, each representing a structure facing potential demolition.
The Value of Data Transparency
Infrastructure projects serve the public good, but they also carry human costs. By creating and sharing this dataset, we enable:
Property owners to independently verify their risk status
Communities to organize and advocate with evidence
Government to improve compensation and relocation planning
Researchers to analyze patterns and propose alternatives
Media to report with verified, spatial data
Data transparency doesn’t oppose development—it makes development more equitable and accountable.
About the #30DayMapChallenge
The #30DayMapChallenge is a daily mapping and cartography challenge throughout November. Created by Topi Tjukanov, it brings together the global geospatial community to explore creative ways of visualizing spatial data.
This is Day 4: My Data—sharing datasets we’ve created ourselves to address real-world challenges.
Over the next 26 days, we’ll continue exploring Nigeria’s spatial story through different cartographic lenses.
Tomorrow: Day 5 — Earth
We’ll explore Nigeria through planetary-scale perspectives and satellite imagery.
Share This Data
Help spread data transparency for infrastructure accountability.
References
Project Documentation:
Federal Ministry of Works and Housing (2024). Lagos-Calabar Coastal Highway Engineering Plans and Specifications. Federal Republic of Nigeria.
Official Statements:
Channels Television (2024). “Lagos-Calabar Coastal Highway: 750 Houses Marked for Demolition in Lagos - Umahi.” Channels TV News.
Vanguard Nigeria (2024). “Lagos-Calabar Highway: FG to Demolish Over 800 Houses.” Vanguard News.
Project Context and Cost:
Premium Times (2024). “Nigeria Begins Construction of Lagos-Calabar Coastal Highway.” Premium Times Analysis.
BusinessDay (2024). “Lagos-Calabar Coastal Highway: Economic Benefits and Social Costs.” BusinessDay Nigeria.
Legal and Compensation Framework:
Land Use Act (1978). Federal Republic of Nigeria. Laws of the Federation.
National Assembly of Nigeria (2024). “Senate Committee Report on Infrastructure Development and Community Displacement.” Federal Republic of Nigeria.
Technical Tools:
Protomaps (2024). PMTiles Specification v3. PMTiles Documentation.
MapLibre Organization (2024). MapLibre GL JS Documentation. MapLibre GL JS.
Data Citation:
Nexus Engineering & Planning Ltd. (2024). “Lagos-Calabar Coastal Highway Buildings at Risk Dataset.” Created through spatial analysis of Federal Ministry of Works engineering plans. 2,553 building footprints, 946 PMTiles, zoom levels 10-18. Dataset Access.
Want to explore Nigeria’s spatial data? Contact us
Follow our #30DayMapChallenge series: Nexus Insights