Spatial interpolation in QGIS
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- Опубліковано 7 кві 2020
- This video demonstrates how to intepolate point vector data to raster using two methods in QGIS. First nearest neighbour interpolation is used, which creates so-called Thiessen polygons. The second interpolator we used is the IDW method. Results are compared and discussed.
This video was part of the second QGISHydro Webinar with Kruth Menke and Hans van der Kwast. The full video can found here: • QGISHydro Webinar 2: I...
More free materials can be found at IHE Delft OpenCourseWare: www.gisopencourseware.org
(c) OpenStreetMap Contributors
I've done my bachelor's dissertation using both interpolation methods. Your videos were really helpful for me during those times. I want to thank you.
Hans, ontzettend bedankt voor de duidelijke en informatieve filmpjes! :)
As always - a very helpful, well-explained video, thanks!
I really like your explanations, thanks
Thank you Professor Hans
you saved mine life
tnx
That 3D was great Thx
Thanks very much for the useful tutorial. Can we edit the extent of the raster layer when choosing the Nearest neighbor interpolation method?
good wishes sir
this tutorial was awesome as usual
can i know how to use theissen polygon for finding Avg. DIALY rainfall by having the data of annual rainfall at each station using QGIS ?
please tell me or give me any tutorial link sir
Can you explain further on the use of adiabatic lapse rate for areas with differential Elevation profiles
This is very useful video. I am not aware of the dataset or problem being studied. Wish there was a very brief intro of the dataset or an example problem.
Thank you once again for your video
Here's the full context: ua-cam.com/video/84cq3CmBwck/v-deo.html
This exercise is needed if you have point data and you want to have full coverage of an area. Then you need to interpolate the points to raster. 2 methods are demonstrated. In this case for temperature data of the Netherlands.
Here's another example for goundwater levels in boreholes: ua-cam.com/video/CqyK_QsasSI/v-deo.html
Hi Hans, I want to try the "Grid Inverse distance to a power", but the option isn't in my menu. (I have just installed 3.12.3). I do have the other three options (moving average, data metrics, nearest neighbour). Also missing are the bottom two, TPI and TRI. Do you have any idea how to solve this..?
In my 3.12.3 version it shows up. You can try to start QGIS with a clean profile (Settings -> User profiles -> New profile...). Otherwise look for IDW in the Processing Toolbox, that one works in a similar way (Interpolation -> IDW Interpolation OR GDAL -> Raster Analysis -> Grid (IDW with nearest neighbor searching)).
Just a note. I recommend to use the LTR versions for operational use and tutorials. My tutorials are always checked with the Long Term Releases. The current LTR is 3.10.6. Newer versions have new features, but also new bugs. They are great to try out new stuff.
ERROR 6: Unable to set GeoTransform, SAGA binary grids only support the same cellsize in x-y. (This error appear)
ERROR 6: Unable to set GeoTransform, SAGA binary grids only support the same cellsize in x-y.
@Hans van der Kwast Very useful video indeed. I am trying to interpolate rainfall data. I however have an error 4 message: does not exist in the file system, and is not recognized as a supported dataset name. Please help
Not enough info to understand your problem. You need a vector file (e.g. shapefile or Geopackage) with a decimal field to run the interpolation.
Hi, I have a problem with the TIN. I just started using QGIS because I no longer have access to ArcGIS. I want to create a lake bathymetry map from depth survey points. I created a polyline and converted it to a polygon so I can contain the interpolation within the shoreline boundary but when I run the TIN, it does not recognize the shoreline polygon as the extent and it interpolates out of that. What is wrong?
I don't have much experience with TIN. Maybe this video helps: ua-cam.com/video/NGUWa-sTFkI/v-deo.html
Otherwise ask there.
Dear Sir , Your videos are excellent . Please help me a
video that How can I do in QGIS , to take the spatial average of all the pixels
from the climate data (like maximum temperature or minimum temperature or
rainfall) that lie inside of the boundary of each district using 'Zonal
Statistics as Table' to calculate the average of the given climate variable
within each boundary.
Use Zonal Statistics from the Processing Toolbox. docs.qgis.org/3.10/en/docs/user_manual/processing_algs/qgis/rasteranalysis.html?highlight=zonal%20statistics#zonal-statistics
In nearest neighbour interpolation, after calculating whole area interpolation i couldn't able to run the cliped by mask layer algorithm for my specific area. how to do that?
Make sure that the raster layer and the polygon layer has the same projection. Also the vector layer should have only 1 polygon that you use for clipping.
Hi, how do you set the raster definition when using IDW? The output gives me pixels that are circa 650x650 meters by default which is not enough for my analysis. I don't see any option in the UI to set the grid spacing
I think it's covered in one of my newer videos. If you use IDW from the processing toolbox you can set the extent and pixel size.
@@HansvanderKwast yes I figured out, the IDW from the menu bar is different from the one in the toolbox panel, thanks!
Hello, i have an error message when i run the function : "Failed to find field Z on layer TEST, skipping.
Le processus a renvoyé le code erreur 1"
Not sure which tool, but make sure you choose a valid numeric field for the interpolation.
Which interpolation technique will be better if I have a TRMM gridded rainfall data set?
If it's gridded data you don't need to interpolate.
@@HansvanderKwast Thanks!
Hi, how did you add your values (temp) to your location points for the analysis to measure?
Hi. That was done by joining 2 attribute table as shown in this video: ua-cam.com/video/aTEHmZqpqC0/v-deo.html
Here's the full webinar: ua-cam.com/video/84cq3CmBwck/v-deo.html
@@HansvanderKwast Hi thank you so much for your response. I will have a look at this
Hi Hans, Thank you so much for making these video tutorials. I had zero knowledge on QGIS or GIS software, now I am learning from your video lessons. However, after upgrading the QGIS version from 3.10 to 3.12, I am having trouble opening and every time I am getting error message. Such as "2020-04-09T11:10:35 WARNING Python error : Couldn't load plugin 'wntOS-3' due to an error when calling its classFactory() method See message log (Python Error) for more details. 2020-04-09T11:10:52 INFO Executing" Could you please help me to resolve this issue? Appreciate your time and help. Thanks
Please note that my course materials work guaranteed for QGIS LTR versions (Long Term Release). These versions are bug fixed and for courses and operational use. Newer versions have new features, but can also introduce new bugs. They are experimental. You can help the programmers to report those issues on GitHub.
Hans van der Kwast Thank you for your hints.
Sir
I'm a beginner and would like to ask how do we get the station?
The data is provided with the book QGIS for Hydrological Applications (www.locatepress.com/hyd). But the methods will work with other point data too that you can find on the internet or collect in the field.
@@HansvanderKwast Thank you so much
Why no one can make a video about interpolation kriging
Kriging is an advanced method where you need knowledge about the spatial correlation of your data, because kriging is based on the semi-variogram. You also need enough sample points, otherwise the semi-variogram will not be fitted well. Lastly, QGIS doesn't offer well documented tools to apply kriging to your data. You can try the SAGA tools from the processing toolbox, but they are hard to apply without knowing what the parameters mean and when you can't fit a semi-variogram. When I do kriging I use R and I can recommend to use that instead of desktop GIS software. Here's a video: ua-cam.com/video/jfZKqO4TBtw/v-deo.html
But you can find many tutorials on the internet on how to use R for kriging.
What plugins we need to install for Interpolation
As you can see in the video, these interpolation algorithms are included in QGIS. So no need to install plugins.
@@HansvanderKwast how can we do interpolation using latest version of QGIS, as It has different interface so i am finding it difficult to learn
@@preetamrawat1389 On my computer it looks the same in 3.10.6, 3.12.3 and 3.13.0, so not sure why it's different for you. Menu: Raster -> Analysis -> Grid (...). Alternatively you can find them in the Processing Toolbox. But better check your installation if the menu is incomplete.
in nearest neighbor option how to choose then "z value from field"
In the dialog expand the Advanced Parameters section. There you can choose Z value from field.
thank you sir@@HansvanderKwast
16.7 °C... warm... so funny!!