Land Cover Mapping of Anambra State Using Sentinel-2 Satellite Imagery

To understand the surface of our planet, scientists distinguish between what the land is made of and what covers it. The ground itself might be rock or soil, but the "land cover" is the material sitting on top: the grass, the concrete, the water, or the crops. Knowing exactly what covers the ground is not just an academic exercise; it is the foundation for managing resources, planning cities, and protecting the environment. When forests disappear or wetlands are filled in, the balance of the local ecosystem shifts, often with consequences for flooding, agriculture, and wildlife. To track these changes efficiently over vast areas, researchers turn to satellites. These orbiting cameras capture detailed images of the Earth, allowing scientists to see patterns that are impossible to spot from the ground. By analyzing these images with computer software, they can sort the landscape into distinct categories, creating a map that tells a story about how humans and nature share the same space.

In a recent study focused on Anambra State in southeastern Nigeria, a team of researchers from Nnamdi Azikiwe University set out to create a fresh, detailed picture of the land cover in their region. The state, home to bustling markets and diverse landscapes ranging from river valleys to hills, has been changing rapidly due to urbanization and farming. However, the existing maps were outdated, making it difficult for local planners to manage growth or protect natural resources effectively. To solve this, the team used high-resolution images from the Sentinel-2 satellite, which circles the Earth every five days and captures details as small as ten meters across. They downloaded four large image tiles that covered the entire country and stitched them together to form a complete view of Anambra State. Using specialized mapping software, they trimmed the image to the state's exact borders and then taught the computer to recognize the different textures and colors of the ground. The software sorted the landscape into seven specific categories: water bodies, vegetation, flooded vegetation, crops and farmlands, built-up areas like cities and towns, bare ground, and rangeland.

The resulting map revealed a landscape in transition, dominated by a mix of human activity and natural growth. The largest single category was rangeland, which covered 38 percent of the state, followed closely by built-up areas at 26 percent and vegetation at roughly 26 percent. Farmlands made up about 6 percent, while water bodies, flooded vegetation, and bare ground occupied much smaller portions of the total area. The researchers found that the expansion of cities and farms is happening at the expense of natural vegetation, a shift that carries significant risks. As trees and natural ground cover disappear, the land loses its ability to absorb water, which can lead to more severe flooding and soil erosion. The map also highlighted areas of flooded vegetation, signaling regions that are particularly vulnerable to rising water levels, a critical piece of information for protecting homes and infrastructure.

To ensure the map was trustworthy, the team checked their work against real-world data. They compared the computer's classification with known locations on the ground, a process that confirmed the map was highly accurate. The final result was correct 88 percent of the time, with a statistical measure of agreement reaching 83 percent. This level of precision means the map can be relied upon for serious decision-making. The study concludes that this updated view of Anambra State is a vital tool for local authorities. By using this clear, data-driven picture of the land, planners can guide sustainable development, protect the environment, and manage the state's resources more effectively, ensuring that the rapid growth of the region does not come at the cost of its ecological health.