How do we know where we are?
Co-ordinate reference systems (CRS) are the key information that allows QGIS to display our geospatial data in positions that reflect the real world. In order to be able to map a point, line or polygon you need to be able to describe its position in terms of a pair of co-ordinates.
However mapping a complex 3D shape to the 2D surface of our computer screens or paper is no simple matter and there are many, many co-ordinate reference systems available. Take a look at our introductory video below and try your hand at our Co-ordinate Battleships Game for fun way to highlight the importance of the CRS in GIS.
If you want to try the Co-Ordinate Battleships game you can print a copy of the grid and instructions from the link to the right.
CRS – Seeing the difference
The Comparing Map Projections interactive website allows you to view the impact of various co-ordinate systems on the presentation of global land and sea mass.
Work though the sections below to find out more about our most commonly used CRS.