 Hello, this is Hans van der Kwas senior lecturer at IHC Delft Institute for Water Education. In this video I will show you how to find the EPSG code for your projection that you use in your project in GIS. In the past we had to manually choose our projections from the graphical use interface or use many different parameters to define it from the command line. This caused a lot of confusion among different projections within the same project. Nowadays most GIS systems use EPSG codes as spatial reference system identifiers, or ESRITs. And EPSG definition data for identifying projections and performing transformations between these systems, while some also support ESRITs issued by other organizations, such as ESRI. Here in QGIS we use the EPSG codes, which is a public registry of spatial reference systems, Earth ellipsoids, coordinate transformers and related units of measurement. Each entity is assigned an EPSG code between 1024 and 32,767, along with a standard machine readable well-known text representation. This catalog is actively maintained by the IOGP Geometrics Committee, where IOGP stands for International Association of Oil and Gas Producers. For example, if we would like to represent a Dutch projection in an EPSG code, we use the code 28992, which then represents Amersfoort, Rijksriukstelsel, and then a new version. There's also an old version, which has a different number. So by just using this number, we standardize the use of the correct projection. If we want to use the UTM zone that covers the Netherlands, zone 31 North, with the datum WGS84, we use the EPSG code 32631. The codes are also a bit standardized, so 32 stands for UTM on WGS84, and 6 is for Northern Hemisphere, and 7 for Southern Hemisphere, and then 31 is the zone number. If we want to use the geographic coordinate system on WGS84, so with the unit's latitude longitude, we use the EPSG code 4326. So how can we find the EPSG code of our project? Of your work in a certain country, you can always check with the mapping agency which projection is used, and maybe they even know the EPSG code. Often however, that is not feasible. Then you can use these different websites. With spatialreference.org you can search with keywords of the projection in the EPSG catalog. With the second website, EPSG.io, you can look up a country or a region and see which EPSG codes are most often used in that area. If you already have a file, like a shapefile, with a PRJ file, you can upload it to prj2EPSG.org, and it will return the EPSG code. Now I will demonstrate these different websites. The first website that I want to demonstrate is spatialreference.org, which is basically a search engine on top of the EPSG catalog. In the search field, you can type keywords of the projection that you're looking for, such as the projection name and the datum. However, you need to be very precise. It's not like Google that it can guess what you mean, so you can do a bit of trial and error to find out how to write different keywords. So here you see the example for UTM, so 31 North, WGS, and we're looking for WGS84. We see that it also reports other IDs instead of the EPSG. In GIS, we often use the EPSG codes. When I click on the EPSG code, I get the description, and I can export it to different other formats for projections. But for use in QGIS, for example, it's enough to simply copy this EPSG code and share it also with your project members. The second website that I want to demonstrate is EPSG.io. It's an open source project, which makes it easy to look for EPSG codes and projections using also the names of regions and countries. So when I search for Netherlands, I get some results of the most often used EPSG codes in the country. And then still, of course, you need to compare it a bit and find out which one is the one that you really want to use. So here there's the Amos Fort, like Drugstahlsson, new, and it comes with the location of that projection so you can check and it displays in different formats the properties of the projection. The last one that I want to demonstrate is PRJ to EPSG, where you can simply upload the PRJ file that sometimes comes with your shape file. If you have that, you just upload it, click Convert, and it will return in the well-known text format your projection, but at the bottom it will also report your EPSG code, in this case 32632, which is UTM Zone 32 North on WGS84, which can also be read from the well-known text format. In this video you've learned what the EPSG code is and how useful that is in GIS to standardize the projection in a project and share it with your colleagues, and three different websites where you can find your projection and the EPSG code. I hope you enjoyed the video and please subscribe to my YouTube channel if you want to get updates for new videos and you can find more free materials at GISOpenCourseWare.org.