At this second module, the last theoretical one before starting with the practical part, we will speak about reference systems and how we can apply them in a GIS to represent our geographic information correctly.
It is very important to know about this issue because if we load two layers that are in different reference systems, in a same view, we can have them without being overlapped correctly. We will have to manage their reference systems to solve this problem.
Reference systems can be managed in different ways, and one of the most used options is through EPSG codes, where each different reference system is corresponding to a different code.
At this link you can see the list of EPSG codes of the different reference systems, that will help you to work with your cartography in gvSIG: http://downloads.gvsig.org/download/geodata/EPSG_codes/Projected_Coordinate_Reference_Systems.pdf
And here you have the video of this second module: