Introduction to basic but important concepts about Coordinate Reference Systems (what is doable in 20 min ) - Geographic Coordinate (Reference) Systems - Different Datums/Ellipsoids - Projections (Mercator, UTM, LCC, ...) - EPSG catalog - WKT (well known text) description - Reference to PROJ.org library The purpose is to explain basic concepts to have a good basis to understand later more complex problems. The presentation will have a lot of links to go deeper into any area of interest. Chapters: 0:00 Introduction 0:30 Agenda 1:05 Why do we need Coordinate Reference Systems? 2:08 Model of the Earth - Geographic CRS 6:42 Projections 9:50 Equirectangular projection 11:06 Tissot's indicatrix 11:50 Mercator projection 13:44 Transverse Mercator projection 14:10 UTM 14:57 Lambert Conformal Conic 15:40 Projected CRS 16:53 EPSG 17:45 WKT 19:24 PROJ