QGIS Data Prep Done Right: CRS, EPSG Codes, Clipping & GeoPackage

Coordinate systems are where most GIS work quietly goes wrong. In this walkthrough, Francis Otia takes you through reprojecting layers, reading EPSG codes, the difference between reprojecting and assigning a coordinate system (two things that are easy to confuse and expensive to get wrong), clipping cleanly, and saving your work as a GeoPackage instead of a Shapefile. Follow along with your own data. By the end you will be able to check any layer's coordinate information, prepare it correctly before clipping, and store it in a format that holds up. This session is part of GeoDev Lab Africa, a free twelve-month guild that turns GIS analysts into geospatial developers. Learn. Build. Collaborate. Transform. Chapters 00:00 Intro 00:30 Reprojecting a layer 02:24 Calculating area in square metres 02:34 Using the Raster Calculator 04:42 Inspecting coordinate information 05:41 EPSG codes and how to read them 06:04 Reproject vs assigning a coordinate system 07:33 The 5 data quality questions 08:08 What to do before clipping a layer 09:42 Clipping a layer 12:28 Saving a layer as GeoPackage 14:03 Why GeoPackage? 14:26 Inspecting the attribute table Presented by Francis Otia, GIS Consultant specialising in spatial analysis, site selection, Web GIS and remote sensing, and a 2026 Global Climate Geodesign Competition finalist. Join the guild YouTube: @geodevlabafrica LinkedIn: linkedin.com/company/geodev-lab Instagram: @geodev_lab X: @geodevlabafrica #QGIS #GIS #CoordinateSystems #GeoPackage #RemoteSensing