 Hello, this is Hans van der Kwasz, senior lecturer at the I.G. Delft Institute for Water Education. In this video I am going to explain vector overlay. In the vector geoprocessing tools you can find different tools to do vector overlays, such as clip, union, intersect and difference. Here I have two polygon layers, a circle and a square. I have created separate attribute tables so we can compare what happens with the attributes after the overlays. In the vector menu we find the geoprocessing tools. The first step we are going to try is the clip tool. I am going to clip the square with the circle. Let's have a look at the results. We see that the overlapping part between the square and the circle has been clipped. We can see that that part has the attributes of the square because we clipped the square with the circle. The second one that we are going to try is the difference tool. We use the square as the input and we use the circle as an overlay to calculate the difference. Let's check the result and we see that now the circle is cut out of the square. Let's check the attribute table. We see in the attribute table that the attributes of the square are kept. Now we are going to do an intersection. We use the square as an input and we overlay with the circle. Now we have a part of the square that overlaps with the circle. Let's check the attribute table. We see that it combines the attribute table of both polygons. Also intersect combines the overlapping part of the attribute table and of the geometry. Now let's do union. We choose the square as the input and the circle as the overlay. With union now we see three polygons. We see the large part of the square. We see a part where the square overlaps with the circle and we see the circle. If we look at the attribute table we have the three features with the combined attributes. So where there's only the circle we get the attributes of the circle, where the circle and the square overlap we get both and where there's only the square we only get attributes of the square. The last one is the symmetrical difference. We use square as an input and the circle as the overlay layer. Now we see that the overlapping part has been made no data and the other parts are kept. If we look at the attribute table then we can see that the two separate attributes have been kept but the overlapping part is not a feature and there are no combined attributes. I hope this was useful. Please subscribe to my YouTube channel if you want to see more videos and get updates and for more free course materials go to IHE Delft OpenCourseWare at GISOpenCourseWare.org.