how to turn a raster basin from a DEM into a polygon shapefile, you’re in the right place. This tutorial from GeoJamal TV breaks down the process
If you're new to GIS and trying to figure out how to turn a raster basin from a DEM into a polygon shapefile, you’re in the right place. This tutorial from GeoJamal TV breaks down the process into two easy steps: reclassify your raster, then convert it into a polygon shapefile.
🎥 Video Tutorial: How to convert a raster to polygon
Watch the full tutorial:
Watch the tutorial on YouTube
🔧 Tools You’ll Need
- QGIS (Free and Open Source) or ArcGIS
- Raster with basin data (DEM-based)
- Basic knowledge of raster tools
📝 Step-by-Step Instructions
- Load your basin raster (e.g., a watershed output from DEM processing).
- Reclassify the raster using Raster calculator, Con or Reclassify tool:
"raster_layer_name" > 0— this sets all basin areas to1, others to0. - Run the Raster to Polygon tool to convert the binary raster into vector format.
- Delete all polygons that are outside the basin — you usually only need the largest one.
- Export the result as a Shapefile (*.shp).
📌 Why This is Important
Turning your raster into a shapefile is an essential step in many GIS workflows because it allows you to use the basin as a precise boundary for mapping, spatial analysis, and data extraction. With a shapefile, you can easily clip and analyze other datasets—such as land use, rainfall, or population—specifically within the basin area. It also helps you generate cleaner, more professional map outputs. This process is widely applied in real-world scenarios like flood risk mapping, watershed modeling, and land use planning inside hydrological basins, making it a critical skill for both environmental analysts and GIS professionals.
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