QGIS 101: Cubic Spline Interpolation of static water levels

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Geosearch International

Күн бұрын

Пікірлер: 27

@cusco4x295 2 жыл бұрын

Hi André. Many thanks for your video. Helps me a lot.

@GeosearchInternational 2 жыл бұрын

You are welcome! All the best, Andreas

@mahsa.k96 Жыл бұрын

hello , and thanks for useful videos , can I use this methode to interpolate temperature data (by considering elevation as a variable )?

@GeosearchInternational Жыл бұрын

You are welcome Mahsa. The cubic spline interpolation is only good if you have a lot of data points, which can be a bit noisy. For temperature I would use the Thin Plate Spline (TPS)- see kzbin.info/www/bejne/f5ObfoRsbd2Yo7s. However this only uses the data points. If you want to correct for elevation, then you should use multivariate methods. I think there are tools in GRASS for this which may work in QGIS. Also have a look at this publication: www.researchgate.net/publication/220606110_Multivariate_Interpolation_of_Precipitation_Using_Regularized_Spline_with_Tension Why do you want to do this excessive? You could also download the 500x500m pixel size MODIS temperature data since Jan 2000. You can use the methodology shown in this video on ET: kzbin.info/www/bejne/mYakpYyvfK5so6s Good luck and all the best, Andreas

@mahsa.k96 Жыл бұрын

@@GeosearchInternational thank you very much for your reply , I am doing my master thesis and as the area of the study is a mountain area and it is dependent on elevation , I want to consider it as variable , the problem is that the number of measurment stations are limited (26) in this area and I dont know how can I do the interpolation and which methode

@GeosearchInternational Жыл бұрын

@@mahsa.k96 why don't you get the temperature from MODIS for your stations, and it there is a good match you can use MODIS for the project area. All the best, Andreas

@mahsa.k96 Жыл бұрын

@@GeosearchInternational thank you sir ,I am going to try this

@GeosearchInternational Жыл бұрын

Let me know if it works. All the best, Andreas

@ahmadjawid9884 8 ай бұрын

Hi Andreas, I tried to interpolate the groundwater monitoring wells data using the cubic spline method but faced a problem. Please see the attached screenshot on ur email. Can you please guide me on how to proceed?

@GeosearchInternational 8 ай бұрын

Hi Jawid, for groundwater levels I recommend the Thin Plate Spline (TPS) method. See: kzbin.info/www/bejne/f5ObfoRsbd2Yo7s

@jhanolaer8286 2 жыл бұрын

Hi sir,How Do I Connect Two Splines Just Keep On Iterate From First Curve to the Upper Curve?

@GeosearchInternational 2 жыл бұрын

Hi Jhan, Sorry, I don't fully understand your question. The spline interpolation is just an imaginary surface that tries to fit as closely as possible to some data points. If you have a set of data points - for example ground water elevation from a single aquifer - then you should interpolate all these points together as one dataset. I cannot think of any situation where I would want to connect two separate interpolated surfaces in the horizontal axis. In the vertical axis it is a different story, and there we often do it to find, for example, the thickness of an aquifer using the top and bottom surfaces. All the best, Andreas

@debsguerreiro 3 жыл бұрын

When I press run, there is a message that the layer couldn't be generated... I tried to change de values but nothing happend. When I did on SAGA software separatedly it worked. (I'm just starting with geoprocessing) What could it be the problem?

@GeosearchInternational 3 жыл бұрын

Hi Déborah, Have you projected the points? e.g. WGS84 geographic coordinates projected to UTM. Hope it works, Andreas

@debsguerreiro 3 жыл бұрын

@@GeosearchInternational Thank you! But, I projected the vector and the same error appears. The problem it is that all tools letters from SAGA are greyed out. I alredy searched in internet and tried to solve the problem in many ways but it still continues like that. Do you know something about that?

@GeosearchInternational 3 жыл бұрын

Strange that SAGA is not active. Are you using a stable version of QGIS? Maybe you need to reinstall it?

@GeosearchInternational 3 жыл бұрын

Hi Débora, Another possibility is that the numbers you are trying to interpolate are stored as text. Right click your point layer - Open Attribute Table... Numbers will align to the right & text to the left. Obviously the one you want is numbers. I sometimes get this problem in countries where the decimal point is stored as a comma.

@debsguerreiro 3 жыл бұрын

@@GeosearchInternational Hey! Thanks a lot for the tips but it still doesn't works ... My colegues are having the same problem...I'm with the LTR version and tried old ones. In processing it is all activate too...