Working with LiDAR Data in ArcGIS Pro

hello everyone my name is wing chung and i'm a professor of geography and gis at palomar college and also an assistant director of the geotech center in this video we'll go over some basics with working with lidar data in arcgis pro so there are two learning objectives in this demonstration video the first one is to show you how we can create a last or las data set using arcgis pro and the second is to show you some very basic visualization options that you have with your last data sets in arcgis pro if you wish to follow along with this demonstration please download and unzip this very large file at this web address before continuing now keep in mind that you're downloading about five gigabytes worth of data so it's going to take some time to download and also to unzip make sure again that you unzip the file after you have downloaded it otherwise you won't be able to see it or find it in arcgis pro some background information here the data set that we'll be using in this demonstration came from our drone lidar units from goq group and this is a setup called the goq trueview 410 system that was mounted on a dji matrice 600 drone and we flew this unit on the palomar college campus as you can see in this data sheet here something that's worth mentioning is the laser or the lidar beams that this unit is capable of sending out and also the number of returns that is capable of reading or detecting from each of those laser pulses that comes from these lidar channel or lidar beams in particular as you can see here there are eight lidar channels or eight lidar beams and you can think of each of these lidar channels as a device that is able to emit thousands of laser pulses per second and also detect the return or reflectance of these laser pulses that bounced off these surfaces that are on the earth's surface and for each of these thousands of laser pulses that are emitted by each of these eight channels that is in this lidar scanner our lidar scanner can detect up to three returns from each of those laser pulses and what this means is this here for each of the thousands of laser pulses that are sent off by each of those lidar channel you can see that the first return is going to be basically the first reflectance of that laser pulse back to the lidar scanner the second return is the second thing that the laser pulse hit and is returned to the lidar scanner and the last return in this case the fifth return is the last thing that the laser pulse hits and its return to the laser scanner not necessarily all laser scanner as in the case with the one that we're using to capture the data that we're working with in this demonstration is capable of detecting five returns from each laser pulse in our case the quantity m8 is only capable of detecting three returns so now let's move on to part one of this demonstration video creating a lidar data set in arcgis pro to do this we need to open our js pro and start a new map and i'm going to go ahead and call this lidar one and i'm going to put this in my folder here and if you have not heard of the term lidar before lidar stands for light detection and ranging and it's basically a technique where the laser scanner like i mentioned before shoots out these laser pulses and measure the amount of time that it takes for those laser pulses to be returned to the scanner and depending on the amount of time that it takes for those laser pulses to be returned to the scanner that is how the laser scanner figure out how tall these surfaces are so now that we have open our new project we can go to analysis and go to tools and look for the create last data set tool and then we'll navigate to the files that you downloaded and unzipped so in particular this is the file that we want the one that has 201416 in there and then we need to specify where we want to put the output and i'm going to go ahead and say that i want to put the output here in this g197 folder that i'll call it palomar and then make sure that this compute statistics box is checked and then click the run button here and what this process is basically doing is it is just creating a container for our last file which came from the lidar unit in arcgis and so once that is complete you see you should see a red box showing the extent of that last data set that was captured by our drone ladder units and right now you may not be able to see any of the points that are created and recorded in this last data set but if you zoom in you can see here are the points that is part of this last data sets and just like what i was mentioning before each of these points each of these individual dots is created based on the reflectance of these laser pulses back to the laser scanner that is on the drone so again the channels on the lidar units on the drone send out these laser pulses these laser pulses bounced off these objects that are on the ground and gets reflected back to the laser scanner and each of these reflectances or bounces is registered as a point and by putting all of these points together you can see we can come up with some kind of visualization and this is why this is called point cloud because these visualizations were created by taking millions of these points and putting them together so once you're done with creating the last data set let's go ahead and save the project and now we can move on to the second part of this demonstration video which is exploring different last data set visualization options using arcgis pro so now we go back to arcgis pro go to the contents pane and you should see this palomar dot lasd or last data set layer that was created as a result of what we did in part one of this demonstration now we go to appearance because you can see in this contextual ribbon since we have a last data set selected we have a last data set layer tab that just created for us in the ribbon of the arcgis pro software click appearance and you can see that here we can click on last points and we can select either to show me all the points right based on all the returns will just show me those points that are considered the ground return so you can see by selecting the ground option all those points that are not part of the ground return right are excluded from my visualization like all those points that coincide with this building outline or trees or cars are excluded and only the points that are lower in elevation right because if we expose this you can see the different colors associated with the points are showing us different elevation values so now if we go on and make sure that the last data set is selected and go to last points and now ask arcgis pro to show me just the first return points so just like i went over briefly in the background slides those first return points are the first object that the laser pulse from our scanner came into contact with and if you would like more information about how lidar work or what returns are or what point density intensity are that will be the discussion of a separate video the main goal of this video is to show you how to work with lidar data sets in arcgis pro okay so in addition to just filtering what we see or the points that we see based on is it's classified as the ground or is it classified based on this return number like first returns we can also create some visualization based on our last data sets so again right we have this legend here that shows us the elevation value that corresponds to each of these points colors and let's go back to the last points here and say show us all the points and now we go to symbology this is where we can show our points using different schemes uh or different coloring methods we can color our point based on their return numbers as opposed to coloring our points like what we're doing now based on their elevation value so as i've mentioned before since this particular lidar system that we use are capable of detecting three returns or up to three returns for each of the laser pulses you can see we have return number one two and three and here in this pane we can change how to colorize each of those returns and so you can see we have a lot of points from the first return which is normal and then fewer points that are part of the second return and then even fewer points that are part of the third return so now let's look at some other visualization methods if we go back to symbology you can see we can also visualize our point cloud as a surface an elevation surface so instead of coloring our points based on the elevation registered at those point location we can also build a triangulated irregular network or tin model based on the height or elevation register at each of these point locations if we really zoom in you can see each of these surfaces takes the form of a triangle and the triangle is created by connecting three points at that location so now we zoom out you basically get a 3d mesh or a tin model that is showing you elevation of the area we can still filter the points in our data set by their class just like what we have done previously so we go back to last points here and say just show me the elevation surface that is created by all the points that were classified as ground by the software you can see the software strip away all of those points that are not considered part of the ground and then use the remaining points to create this tin model or this elevation surface that's is based on the points that are classified as ground and so this is very important because this allows us to basically erase all the non-ground features from our study area so in addition other options for visualizations includes again if we go back to symbology we can also visualize our layer as a slope surface to allow us to see the changes in elevation across our study area right so you can see that here in particular in some areas where there is a incline right it has a greater slope value and then lastly we can also visualize elevation information as contour lines all right so let's decrease the interval since there's not much elevation changes in this area just so that we can see some lines and so you can see right instead of using different color points or different color triangles to represent that elevation change information we can now represent that elevation change information using contour lines and again we can save this project if you'd like and this concludes our short demonstration on how do we create a last data set based on a last file for more information about lidar data or other topics in gis please visit the geotech center website thank you for watching

Channel: GeoTech Center Concept Modules

Views: 549

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Id: W_kDEKAsUzg

Length: 15min 46sec (946 seconds)

Published: Wed Oct 06 2021