In this post, I will outline techniques for computing weighted-centroids in both QGIS and Google Earth Engine. For a polygon feature, the centroid is the geometric center. It can also be thought of as the average coordinate of all points within the polygon. There are some uses cases where you may want to compute a weighted-centroid where some parts of the polygon gets higher ‘weight’ than others. The main use-case is to calculate a population-weighted centroid. One can also use Night Lights data as a proxy for urbanized population and calculate a nightlights-weighted centroid. Some applications include:

  • Regional Planning: Locate the population-weighted centroid to know the most accessible location from the region.
  • Network Analysis: For generating demand points in location-allocation analysis, you need to convert demands from regions to points. It preferable to compute populated-weighted centroids for a more accurate analysis.

Do check out this twitter-thread by Raj Bhagat P for more discussion on weighted centroids.

Different Weighted Centroids for the State of Karnataka, India (2015)
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I recently taught a 1-month long course on GIS Applications in Urban and Regional Planning. We explored how GIS can be applied to solve problems in 6 different thematic areas. In this post, I will outline different applications and show concrete examples of using open-datasets and open-source GIS software QGIS.

Here are the 6 thematic areas

  • Land Use Planning and Management
  • Crime Mapping and Analysis
  • Solid Waste Management
  • Urban Infrastructure and Utilities
  • Urban Transportation
  • Spatial Planning
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