Point cloud processing in QGIS 3.32: a practical overview for LiDAR data

hi and welcome to another episode of days from the G this is your host Edward ratell and today we will talk about lighter processing in qjs 3.32 and the first thing to do is to have a nice [Music] lighter let me show you something before this is the cloud we are we're going to work on using qjs this is open in uh C compare actually this is a clip from a larger file but it's quite Danse and at this moment qjs has a few hiss to index uh big clouds in my opinion so to to take a look to very big files Cloud compare is still better and it actually works in 3D but let's move with uh let's move on on um qjs and let's take a file that file uh it will uh drag in a file a lighter file in uh qjs will bring uh red Dash square and qgs will start indexing that file and actually it uh does another thing it creates a companion file in the cloud oriented Point Cloud format and it is also compressed and this allow qjs to do this um very fast rendering but it takes a while like I said before to create this kind of rendering so if you drop a really large file you will uh have to wait a bit so the news in this version uh is found in the processing toolbox so if you don't have a processing tool boox open open it with the toolbox button here in on the top of the center of the toolbar and you will find three sections Point Cloud conversion Point cloud data management and point Cloud extraction the first thing is to gain information about the cloud if we double click information under data management in the processing tool box um dialogue will pop up and we will choose choose the input layer qgs tutorial and we we will click run and clicking run you will get some information it's a last one dot one two uh with a point format three has about 1 million half points uh you can see the offset the extent and an interesting information is that we don't have CRS set and we have a lot of attributes so um we may uh go on uh with uh the assign projection data management and if you uh pay attention here you will see qgs blaming that uh the CRS was undefined so uh we need to fix that uh as the first thing click assign proection uh in the point clown data management here in the processing tool box and then select the input layer qjs tutorial and the desired CRS in this case will be the r&t uh RGN 2008 is actually r&t in Italy and the output layer will be a temporary one but okay let's persist it after uh okay it will use P wrench uh as you can see here it calls P wrench with a translate um assign the CRS espg 67088 with using 12 threads okay so now we have here the output layer we may um shize this uh say oh sorry oh save as and last Point Cloud let's save it in the usual folder the ligher and we may call it qgis tutorial reference okay perfect okay okay let's wait a bit it takes a few seconds for about 2 million points it depends on your computer performance and you will get it index set as well as you can see here this is referenced and we have a copy in the CC format okay let's take the out let's set the espg to the the right one okay let's import again the the file as you can see now qgs will not blame anymore and we may want for instance to reproject this uh it's quite easy so you have to select your target CRS maybe we want to move it into the um another Zone uh wgs84 zone 32 North and we may click run and after a while you will find a new file which is reprojected uh actually overlaying the old one but it is in another projection also we can I'm can take this out so okay uh qgs tutorial reference is our file and we may want to do uh an tiling if you think to a 50 million points Cloud uh you want to split it so you may want to um select your input layer you may have more than one and you create a regular grid for this you can change ass sign yours we can keep the right one and we may want to change the side length to 100 meter and let's save to Temple to a directory so let's create a new one called diving and let's save it in here let's click run oh that's not good okay let me restart qjs uh with this occasion I'll um I should tell you that uh when you use a new software you may find some bugs and it should be okay now okay let me try this it's a new software so okay now it's working restarting qjs always okay now if you take a look oh I have do a little error okay let me let me put 50 m the input layers it's always the same okay and let's assign a CRS and always the same directory let's click run okay perfect now we have a few files more let me take a oops let me take this out and import that in qjs so as you can see now we have a a tiling of the The Zone and we have a few F being created from qjs actually from P rench this is a nice front end uh okay now we can for instance change some something okay just this two we want to merge that and we may want to merge two and one D zero okay let me click okay we may want to filter an expression if you want to filter something about um the classification for instance or the intensity or the color and we can also set the proper nextdent but we don't care actually right now so let's click run it will call uh P range and we it will fail so why the heck is failing uh cropping extent is from uh layout map no okay let's put a COR in extent no it it crashed take out save to a file I call it mer Mero okay not using a temporary file works and the we have the file merged here so we have merged two ties in one and this is uh great because you can extract portions of files also let's move to the let me remove that all of that and let's enable the first one we can also clip a Lether file but to do that we need to have a clipping polygon so let's create a new Vector temporary layer so layer create layer temporary scratch um polygon here cting okay no no other things perfect let's add a nice feature a squared one we may want it here okay we may want to save it uh it blames it cannot open the file so let's save and try it again oh no still nothing this is the okay ship files okay let's put it in the same directory here okay cut okay let's let me edit again for safety reasons okay let's input layer cut okay let's run again uh it want work so maybe we want to switch to uh a file cut run okay it's working as as you can see here we have the cut which has been which we wanted and it actually works so let's move on again with another possible feature here you may want to okay let me enable this again uh you may want to filter something you may want to filter by intensity where we want only intensity uh which is uh above 100 and let's click run if oh no so this is this version needs to have file saved so let's save the file in a file and it will works uh they will probably fix this if you want to uh investigate a bit take a look to the source of GJ yes and fix it uh so this is nice because it's open source okay now it's filtered as you can see we have only the intensity above um 100 and we may also have the density and density is uh a nice uh um way to create a Ruster where each cells contain the numbers of point and let's save it to a file because we don't want to surprises anymore let's click run with the as you can see you can see where points are more than than the other parts so where it's black there is only a few points where is White there is about um 2,000 points this is good to have a few metrics in uh in an easy way so for Quality checking boundary also uh it computes the boundary of the the lier so let's save to a file to see let's go bounce and wait a bit okay and it actually it's wrong so it is the boundary should be the nerous shape of the points uh maybe we have some sort of scattering but it should not be and I will investigate further uh about this this is interesting it may be a bug of pedal so okay okay let's move on you may also want to export as a roster and you may use uh few attributes to do that and the X the y z intensity usually we like intensity and the density of the raster is 1 pixel per meter the ti size is uh intended to be the side of the tile that use per tread and advanced parameters we don't care about that okay let's uh use a Ruster here let's input Ruster here click run and okay this is a representation of the the lier in a file so it's quite nice to have to create an image using the lier itself so we can convert format and you can change the format you want want save to a file you may start with the last file which is uncompressed to uh create a one which is compressed or it is another format which is a cloud oriented Point Cloud which is actually a noock tree with made by uh small Las fuz and we may want to create that and the other one is a virtual Point Cloud so it's a cloud is wrapper or many files so you open one and you you have a proxy for other files it's in automatically okay okay no uh if you want to do to do that it's wrong okay Run Okay okay something wrong happened here so let's try with the LA file alone let's file it's working well if you want a c OBC we may want to use the uh create copc and may want to input layer here okay let's run it's already created so there is no problem uh this command is quite useful if you don't have um a copc because if we take out the copc here and we want to create it you may want to uh select the uh qg tutorial reference L as a file which is not actually loaded in qjs I deleted this in the index let's click okay and let's click click run it will take a while to do that and after uh this process you may want to uh import the file in qjs I will open it up in in a second uh so you prepare the file here which is uh really nice uh the last thing I want to talk about is the th operator we can work by something radius or by skipping points let's take a look you may want to set number of point to skip maybe four and let's look in one okay no no I want a last file so let's okay let's edit this let's click Run Okay as you can see we have less density because we are skipping Four Points so keep skip a point and add a point skip four and so on the other thing we can do I'll keep thing one is working by SLE radius maybe we want the point every simp radius so 2.5 so it's a something radius is 2 m and half let's save it to a file let's call it th th two this time as sat as here Run Okay as you can see it's very Cor course you can change it obviously let's do it again using this one uh one meter is okay now uh let's thing to okay run okay it is a bit denser you can um choose your operators to OB whatever you want so okay this is a nice uh overview of the tools in qjs uh actually qjx in this phase is uh a wrapper of the the old uh P stuff so it is uh nice to have have but not fundamental my opinion the really nice thing is to have all the instruments and tools in one place so with time we will see more and more feature about Cloud um Point clouds in qjs this is uh really really good and nice to have so I hope uh this um sure tutorial will uh satisfy you and thank you for listening add a comment if you like and remember to click the like button and to subscribe to the channel thank you for listening

Channel: Tales from the GIS

Views: 4,635

Keywords: gis, geospatial, geographic information systems, gis for beginners, gis tutorial, geolocation, spatial data, qgis for beginners, qgis tips, qgis lessons, qgis lesson, location technology, gis developer, lidar, point cloud, lidar processing, qgis lidar 3d, qgis lidar, qgis lidar processing, qgis lidar tutorial

Id: cz6crZYer6o

Length: 23min 44sec (1424 seconds)

Published: Sat Sep 16 2023