Hello I'm Marc Desgroseilliers from technical support here at Pix4D. Today I'm going to talk to you about measurements. That's one of the great advantage of having an accurate 3d model of your object or scene of interest is that you're going to be able to make measurements. Let's see what are the requirements in a project to be able to make accurate measurements. The first one is to make sure that you have good reconstruction of your model. We discuss this in some other webinars what are the techniques to make sure that your reconstruction is accurate but for example: You can inspect the point cloud make sure that it looks good that its faithful to the scene that you were shooting. But also you want to click a few 3D points and look at the corresponding images and make sure that the reprojection is accurate in the images and it's always at the same point. The other requirement to get good measurements is to have either ground control points (GCPs) or scale constraints. The case of ground control points you want to make sure that: They are well spread out throughout the project - you don't want them clustered in one corner because then the error can accumulate in the other regions of the project - and you also want your GCPs to be around your point of interest. It's a good idea to have one GCP closed to big object that you want to measure for example. Same thing with scale constraint you want them to be around the zone that you'll be measuring; and it's also a good idea to have two or three scale constraints - if you can - , because this will reduce clicking error for example. So in the mapper you can measure three kinds of objects: 1D, 2D and 3D objects by inserting the appropriate object. So you'll be able to measure distances, areas and volumes. In the case of distances you'll be inserting a polyline object. So this is quite straightforward. You'll just be drawing a line in in the project and you'll get the the measurement that is associated; and if you click the endpoints in the images then you'll also get an error estimate for the measurement. The surface object is quite similar in the sense that you will insert a surface and you will get the 2D, 3D length and area. So what do we mean by 2D length, 3D length? Well the 3D length will take into account all three coordinates of your object. So X, Y and Z. Whereas the 2D length or 2D area will only take into account the first two coordinates of your objects. That is the X & Y coordinates. The third kind of object that you can insert in the mapper to get measurement is the volume. So in 2.2 we have a new interface to measure volumes. So you get a new volumes tab. That you can select on the left; and you'll be able to click on the insert volume icon, you'll get a new volume, you insert it in the mapper exactly as you did in previous version. That is clicking to add different vertices of the volume; and you'll get a list of the volumes that you've inserted, with the appropriate measurements. For example fill volume, cut volume and total volume. Then as you can see, there's a little icon that you can click to display the settings associated to a particular volume object. In this settings panel you can set the base altitude of the volume object. So you can set it for example to be the altitude of the lowest point of the volume, the highest point or you can even set a custom altitude for the base of the volume. So this is quite useful for example if you've got slightly more complicated object that you want to to measure. Let's say your volume is on a slope and then you need to be a little bit more careful. So this is an invaluable tool to be able to make measurements in this case. So let's see what this looks like in the mapper. Let's start with adding a polyline to get distance measurement. So let's say that i'm interested in the length of this building here. I would come here at a new polyline. Click it on my rayCloud and right click to finish. As you can see I have my two tie points (MTPs) that are created here. I can refine them by clicking on the images. Now once I've clicked on the images I can click apply. This will update the error estimate for the distances. As you can see i have here the 3D length and 2D length. So that's how you would make distance measurements in the mapper. Let's see now maybe for a surface. So I can find a surface in the project. Let's see, this here, right. I want to insert a new surface. Go left-click, left -click, left-click and then since I want to finish the surface, I'm going to do a right-click. Now you can see the surface here. You can also refine it in the images. You have the information for the 3D area, 2D area. Great! So now let's move on to the third kind of object. Which is maybe the object that interests the most the higher number of people. Those are volumes. So now in Pix4Dmapper 2.2, you have a tab that's devoted to volume measurements. So let's go to this tab. You have it here. Now you see you have your densified point cloud and you can add a volume. So here's my new volume. Let's say I want to measure this stock pile here. So I'm going to start clicking as such. Now I have my volume and I can compute the different characteristics. So I have the cut volume, fill volume and the total volume. If I want I can edit, move, the vertices around a little bit, to make sure that I'm getting exactly what I want to measure. Click compute. Again, I have my statistics here. If I want to adjust the base plane then I would go into settings. As such. It's also possible to add the new volume and so to have many volumes. I can insert new volume. If I want to measure the volume of this truck here. Go compute. That's how you would work with volumes in 2.2. It's also possible to import them and export them. Let me conclude this video by making a few remarks about the way that we make volume measurements in version 2.2 of the software. In this version the volume measurements are exclusively based on the DSM. This allows for more accurate volume measurement, but it also comes with a few caveats. First thing is that you will need to make sure that you ran step 3 and that the DSM is generated before making volume measurements. The second thing to keep in mind is that, if you modify the point cloud and you want these modifications to be reflected in the volume measurements you will need to regenerate the DSM. That is for example run step 3 again to make sure that these modifications are taken into account,and that the volume measurements are updated. I know that a lot of users use these measurement tools and that measurements are very big part of Pix4Dmapper. So i hope that you found this video instructive and that it's going to help you to make good accurate measurements. I'll see you in the next video
