Working with Point Clouds in QGIS: A Step-by-Step Guide
Point clouds are sets of data points in a coordinate system, often representing the external surfaces of objects. In the context of geospatial analysis, point clouds are typically generated using LiDAR technology. QGIS, a popular open-source Geographic Information System (GIS) software, provides tools to visualize and analyze point cloud data. In this guide, we’ll walk you through the steps to work with point clouds in QGIS, incorporating the latest advancements in QGIS 3.32.
1. Setting Up:
Ensure you have the latest version of QGIS installed. Some features might not be available in older versions.
2. Importing Point Cloud Data:
- Launch QGIS and create a new project.
- Navigate to
Add Point Cloud Layer.
- Browse to your point cloud data file (commonly with
.lazextensions) and click
3. Visualizing Point Clouds in 2D:
Once imported, the point cloud layer will appear in the Layers Panel. By default, QGIS will display the point cloud in a 2D view.
4. Switching to 3D View:
- Navigate to
New 3D Map View.
- A new window will pop up displaying the point cloud in 3D. You can navigate using your mouse: left-click to pan, right-click to tilt and rotate, and scroll to zoom.
5. Adjusting Display Settings:
In the 3D view, you can adjust various settings to enhance the visualization:
- Point Size: Adjust the size of individual points for better clarity.
- Color Rendering: Change the color scheme based on attributes like elevation or intensity.
- Point Budget: Determine the number of points displayed. A higher budget will show more detail but may affect performance.
6. Advanced Point Cloud Processing in QGIS 3.32:
With the release of QGIS 3.32, users can now access powerful point cloud algorithms directly within the QGIS Processing framework. Here are some of the new features:
- Convert Formats: Convert point cloud data between LAS and LAZ formats.
- Export to Raster: Export point cloud data to a regularly gridded raster data using inverse distance weighting.
- Export to Vector: Export point cloud data to other vector formats like CSV, Shapefile, and DXF.
- Assign Projection: Assign a projection to a point cloud layer.
- Clip: Clip a point cloud layer by a vector polygon layer.
- Merge: Join multiple point cloud layers into a single file.
- Reproject: Reproject the input file to a different coordinate reference system.
- Thin: Reduce the number of points either by sampling radius or by skipping nearby points.
- Tile: Generate a set of tiles based on the input point cloud layer and tile size.
- Boundary: Generate a (multi)polygon from your point cloud data.
- Density: Output a raster file based on the number of points within each raster cell.
- Filter: Create a new file based on a set filter expression.
7. Behind the Scenes:
All the heavy lifting of point cloud processing in QGIS is done by PDAL, an open-source library for processing point clouds. The new standalone command line tool,
pdal_wrench, built on top of PDAL, simplifies the process, and offers parallel execution for faster processing.
Working with point clouds in QGIS opens up a world of possibilities for geospatial analysis and visualization. With the advancements in QGIS 3.32, users can now access a broader range of tools and algorithms, making the process more efficient and comprehensive.
(FAQs) About working with point clouds in QGIS:
What is a point cloud?
- A point cloud is a collection of data points defined in a three-dimensional coordinate system.
Which file formats does QGIS support for point clouds?
- QGIS commonly supports
.copc formats for point clouds.
How is LiDAR data different from a regular point cloud?
- LiDAR data is a type of point cloud generated using light pulses from a laser. It often includes additional attributes like intensity and return number.
Why is my point cloud not displaying correctly in QGIS?
- This could be due to various reasons, including large file size, incorrect coordinate reference system, or software compatibility issues.
Can I edit point cloud data directly in QGIS?
- QGIS is primarily used for visualization and analysis. Direct editing of point cloud data might require specialized software.
How can I improve the performance of QGIS when working with large point cloud datasets?
- You can adjust the point budget, filter out unnecessary data, or use a more powerful computer.
What is the difference between a Digital Elevation Model (DEM) and a Digital Surface Model (DSM)?
- A DEM represents the bare ground surface without any objects, while a DSM includes the tops of buildings, trees, and other objects.
How do I filter points based on their classification?
- You can use the filter option on the point cloud layer and apply SQL-like queries based on classification attributes.
Can I integrate point cloud data with other GIS layers in QGIS?
- Yes, you can overlay point cloud data with other GIS layers like vector data, raster images, and more.
Is there a way to automate point cloud processing tasks in QGIS?
- Yes, QGIS offers a processing toolbox that allows for batch processing and automation of certain tasks.
How do I change the color scheme of my point cloud visualization?
- You can adjust the color rendering settings based on various attributes of the point cloud data.
Kazi na Point Clouds katika QGIS: Mwongozo wa Hatua kwa Hatua Clouds za Point ni seti za pointi za data katika mfumo wa kuratibu, mara nyingi zinawakilisha nyuso za nje za vitu. Katika muktadha wa uchambuzi wa kijiografia, mawingu ya pointi kwa kawaida hutengenezwa kwa kutumia teknolojia ya LiDAR. QGIS ni programu ya wazi ya chanzo cha wazi ya mfumo wa habari ya kijiografia (GIS) ambayo inatoa zana za kugundua na kuchambua data ya wingu la pointi. Katika mwongozo huu, tutakuongoza kupitia hatua za kufanya kazi na mawingu ya pointi katika QGIS, ikiwa ni pamoja na maendeleo ya hivi karibuni katika QGIS 3.32. 1. Uwe na mtazamo wa kweli Kuanzisha: Hakikisha una toleo la hivi karibuni la QGIS imewekwa. Baadhi ya vipengele inaweza kuwa haipatikani katika matoleo ya zamani. 2. Uwezekano wa kupata Uagizaji Point Cloud Data: - Kuanzisha QGIS na kuunda mradi mpya. - Navigate kwa Kuongeza Point Cloud Layer. - Browse kwa faili yako ya data ya wingu la uhakika (kwa kawaida na.lazextensions) na bonyeza 3. Kuonyesha Point Clouds katika 2D: Baada ya kuingizwa, safu ya wingu la uhakika itaonekana katika Paneli ya Safu. Kwa default, QGIS itaonyesha wingu la pointi katika mtazamo wa 2D. 4. Uwe na uhakika Kuongeza 3D View: Kuongeza 3D Map View Kwa hivyo, dirisha jipya litatokea na kuonyesha wingu la pointi katika 3D. Unaweza kusafiri kwa kutumia panya yako: bonyeza kushoto kwa pan, bonyeza kulia kwa tilt na kuzunguka, na scroll kwa zoom. 5. Uwe na mtazamo mzuri. Kuongeza ukubwa wa picha: Katika 3D, unaweza kurekebisha vipimo mbalimbali ili kuboresha visualization: Ukubwa wa pointi: kurekebisha ukubwa wa pointi binafsi kwa uwazi bora. - Rendering rangi: Badilisha mpango wa rangi kulingana na sifa kama vile urefu au nguvu. - Pointi Bajeti: Kuamua idadi ya pointi kuonyeshwa. Bajeti ya juu itaonyesha maelezo zaidi lakini inaweza kuathiri utendaji. 6. Uwe na uhakika Utaratibu wa Cloud Point Advanced katika QGIS 3.32: Kwa kutolewa kwa QGIS 3.2, watumiaji sasa wanaweza kupata algorithms nguvu za wingu la uhakika moja kwa moja ndani ya mfumo wa usindikaji wa QGIS. Vipengele vya hivi karibuni vya LAS ni: Kubadilisha muundo: Kubadilisha data ya wingu la nukta kati ya muundo wa LAS na LAZ. - Export kwa Raster: Export uhakika wingu data kwa mara kwa mara gridded raster data kutumia inverse umbali uzito. - Export kwa Vector: Export uhakika wingu data kwa format nyingine vector kama CSV, Shapefile, na DXF. - Asign Projection: Asign projection kwa safu ya wingu la uhakika. - Clip: Clip safu ya wingu la uhakika na safu ya vector polygon. - Kuunganisha: Kujiunga tabaka nyingi pointi wingu katika faili moja. -Reproject: Reproject faili ya pembejeo kwa mfumo tofauti coordinate rejea. - nyembamba: Kupunguza idadi ya pointi ama kwa sampuli radius au kwa kuruka pointi karibu. - Tile: kuzalisha seti ya tiles kulingana na pembejeo hatua wingu safu na tile ukubwa. - Mpaka: Kuzalisha (multi) polygons kutoka data yako uhakika wingu. - wiani: Output faili raster kulingana na idadi ya pointi ndani ya kila kiini raster. - Filter: Kuunda faili mpya kulingana na kuweka filter usemi. 7. Uwe na mtazamo gani? Kwa upande mwingine, kwa sababu ya hali ya hali ya hewa, QGIS ina uwezo wa kuunda mawingu ya pointi kwa kutumia PDAL, maktaba ya chanzo wazi ya kuhariri mawingu ya pointi. PDAL ni chombo cha mstari wa amri cha kujitegemea, ambacho kimejengwa juu ya PDAL, na hutoa utekelezaji wa sambamba kwa usindikaji wa haraka. Kufanya kazi na mawingu ya pointi katika QGIS hufungua ulimwengu wa uwezekano wa uchambuzi wa kijiografia na kuona. Kwa maendeleo katika QGIS 3.2, watumiaji sasa wanaweza kupata aina pana ya zana na algorithms, na kufanya mchakato ufanisi zaidi na kina. Kwa nini kutumia Cloud Point katika QGIS? - wingu la uhakika ni mkusanyiko wa pointi data kufafanuliwa katika mfumo wa tatu-dimensional kuratibu. Ni muundo gani wa faili QGIS inasaidia kwa mawingu ya pointi? - QGIS kawaida inasaidia.copc muundo kwa mawingu ya uhakika. Ni nini tofauti kati ya data ya LiDAR na wingu la kawaida la pointi? - LiDAR data ni aina ya wingu la pointi zinazozalishwa kwa kutumia pulses mwanga kutoka laser. Ni mara nyingi ni pamoja na sifa za ziada kama vile nguvu na kurudi idadi. Kwa nini wingu langu la pointi halionyeshi vizuri katika QGIS? - Hii inaweza kuwa kutokana na sababu mbalimbali, ikiwa ni pamoja na ukubwa mkubwa wa faili, makosa kuratibu mfumo wa kumbukumbu, au masuala ya utangamano wa programu. Je, ninaweza kuhariri data ya wingu la uhakika moja kwa moja katika QGIS? QGIS ni moja ya mifumo ya msingi ya utambuzi wa picha na uchambuzi. Uhariri wa moja kwa moja wa data ya wingu la pointi inaweza kuhitaji programu maalum. Jinsi ya kuboresha utendaji wa QGIS wakati wa kufanya kazi na seti kubwa za data za wingu la uhakika? - Unaweza kurekebisha bajeti ya pointi, kuchuja data zisizohitajika, au kutumia kompyuta yenye nguvu zaidi. Ni nini tofauti kati ya Digital Elevation Model (DEM) na Digital Surface Model (DSM)? DEM inawakilisha uso wa ardhi tupu bila vitu yoyote, wakati DSM inajumuisha vilele vya majengo, miti, na vitu vingine. Ninawezaje kuchuja pointi kulingana na uainishaji wao? - Unaweza kutumia chaguo kichujio juu ya hatua wingu safu na kutumia SQL-kama maswali kulingana na sifa uainishaji. Je, ninaweza kuunganisha data ya wingu la pointi na tabaka nyingine za GIS katika QGIS? - Ndiyo, unaweza overlay uhakika wingu data na tabaka nyingine GIS kama data vector, raster picha, na zaidi. Je, kuna njia ya automatiska hatua wingu usindikaji kazi katika QGIS? QGIS inatoa sanduku la zana za usindikaji ambazo zinaruhusu usindikaji wa kundi na automatisering ya kazi fulani. Jinsi gani naweza kubadilisha rangi ya mpango wa mtazamo wangu pointi wingu? - Unaweza kurekebisha rangi rendering mipangilio kulingana na sifa mbalimbali ya data ya wingu uhakika.