What problems do Coordinate Reference Systems help solve?
- Why don’t two datasets of the same area align correctly when you combine them?
- Which coordinate reference system do you use for a specific GIS analysis or map?
- Why can distances and areas be calculated incorrectly when the wrong CRS is used?
- How do you combine geodata from different countries and sources with different coordinate systems?
- How do you transform coordinates without unnecessary loss of accuracy?
- Why does the same geographic information look different in different map projections?
During this Blended Learning course, you’ll learn how locations on Earth are recorded and how Coordinate Reference Systems (CRS) ensure that geodata is placed at the correct geographic position. You’ll discover why different datasets may use different reference systems and what problems arise when these systems are misinterpreted or combined.
You’ll then apply this knowledge in a practical setting using QGIS. You’ll check the CRS of datasets, work with EPSG codes, combine data from different sources, and perform coordinate transformations. This will teach you not only how to set up a CRS, but more importantly, how to assess which reference system is suitable for your geodata and application.
The Theory Behind Coordinate Reference Systems
A coordinate only has meaning when it is known within which reference system it is defined. That is why this Blended Learning course begins with the theoretical foundation behind Coordinate Reference Systems.
You’ll be introduced to geographic coordinates, geodetic reference systems, datums, ellipsoids, and projected coordinate systems. You’ll learn how these concepts are interrelated and why the same location can have different coordinates depending on the system used.
The difference between global and regional reference systems is also covered. Among other things, you’ll learn about WGS84, ETRS89, and the Dutch RD system, and you’ll discover why the choice of a reference system depends on location, application, and desired accuracy.
From the Three-Dimensional Earth to a Two-Dimensional Map
The Earth is three-dimensional, whereas we usually display geographic information on a two-dimensional map or screen. This requires map projections.
You’ll learn how map projections convert geographic coordinates onto a flat surface and why distortions always occur in the process. Distance, area, direction, and shape cannot all be represented completely accurately at the same time.
You’ll be introduced to different types of map projections and learn to assess which properties are important for a specific application. This will enable you to choose a projection that suits the purpose of an analysis or map and understand why an incorrect choice of projection can lead to misleading results.
Working with Spatial Data and Different CRSs
Geodata comes from an increasingly diverse range of sources. Government agencies, satellites, sensors, surveying systems, and open data platforms provide datasets that may use different Coordinate Reference Systems.
You’ll learn how raster and vector data are georeferenced and how information about the CRS used is stored with a dataset. You’ll work with EPSG codes and metadata to determine which reference system belongs to a dataset.
You’ll also learn the important difference between correctly assigning a CRS to a dataset and actually transforming coordinates to a different reference system. This will help you avoid one of the most common mistakes when combining spatial data.
Applying Coordinate Reference Systems in QGIS
After covering the theoretical basics, you’ll get hands-on experience in QGIS. You’ll examine the Coordinate Reference Systems of various datasets and learn how QGIS handles data that doesn’t all use the same CRS.
You’ll work with EPSG codes, set project and layer CRSs, and perform coordinate transformations. In doing so, you’ll combine datasets from different sources and verify that they align geographically.
You’ll also investigate what happens when an incorrect CRS or an unsuitable map projection is intentionally used. This will help you recognize errors that might otherwise easily go unnoticed and could affect spatial analyses, distances, areas, and maps.
Coordinate Reference Systems in Practice
During this Blended Learning course, you’ll work with realistic spatial datasets and real-world problems. You’ll receive datasets from various sources and must determine for yourself which reference systems to use, how they relate to one another, and what transformations are needed to combine the data reliably.
You’ll work on assignments such as:
- Investigate why two geographic datasets of the same area do not align correctly and determine how to solve this problem.
- Identify, based on metadata and EPSG codes, which Coordinate Reference Systems different datasets use.
- Combine datasets in WGS84, ETRS89, and RD within a single QGIS project and evaluate the differences between these systems.
- Transform a dataset to a different coordinate reference system and verify the result.
- Compare different map projections and investigate how they affect shape, distance, and area.
- Select the most appropriate Coordinate Reference System for a real-world scenario and explain why this system is suitable for the analysis in question.
By the end of the course, you will understand how Coordinate Reference Systems, geodetic reference systems, and map projections are related. You will be able to identify and evaluate the CRS of spatial data, correctly combine different datasets, and perform coordinate transformations in QGIS. In addition, you will be able to justify which reference system and which map projection are suitable for a specific Geo-ICT application.
