QGIS 2 Lesson 20 - Using Interpolation to Predict Unknown Values from Known Values in QGIS

* Data available to download from www.dmad.org.tr/qgis-2-lesson-20 *
Hi and welcome to the Lesson 20 in DMAD - Marine Mammals Research Association's second free QGIS course. This course if for beginners to intermediates. In today's lesson we're going to look at interpolating data using an Inverse Distance Weighting or IDW techniques to allow us to predict values between known values. We will use data from weather stations all over Montenegro to predict the values between them. This only a very basic model and doesn't take into account things like elevation but will give you an idea of how interpolation can be used.

[@DiegoAndresAlvarezMarin]

Thank you for your time. It takes a lot of time to do high quality videos like these ones. I learnt a lot from them. Thank you again. See you in part 3.

[@leenariekkola3389]

Thank you so much for these videos, they have been hugely helpful for me! I would absolutely love more courses if you are able to make them (we appreciate that this does mean extra work for you). And I do hope you will keep these videos on KZbin, I have a feeling I will need to come back to check things again and again. Thank you guys!

[@dmadmarinemammalsresearcha3966]

Hi Leena, thank you for the kind words. We are going to continue with at least a short third course but maybe more if we can. And yes the videos will be left up on youtube for a little while so you can keep checking back on them!

[@graysonfernando8272]

A trick: you can watch series on Kaldrostream. Me and my gf have been using it for watching a lot of movies recently.

[@rauljasiah543]

@Grayson Fernando yup, I have been using kaldroStream for years myself :)

[@rodanics273]

Yes please we are looking forward towards advance level of course thank you so much.

[@dmadmarinemammalsresearcha3966]

Hi WIld Eco Tech, thank you for your kind words. DMAD will do our very best to make a third course happen if the demand for it is there

[@meghalperera3381]

These videos have been super useful - really clear and easy to follow. Most courses go from thisissoeasy to whatisgoingon at neck break speed and I've really appreciated you easing into things. You've clarified and solved a lot of issues I had when following previous courses.

[@lolagomezgomez8595]

These videos are brilliant. Thank you very much for all your work and good intention.

[@luciacaldas4587]

Thank you very much for all your effort, I am really enjoying the course! Brilliant format and explanations, really interesting things as well! Will send you an email with my results tomorrow! Thank you once again, amazing work!!

[@dmadmarinemammalsresearcha3966]

Lucía, thank you for your kind words!

[@claravallejo744]

Thank you so much !!

[@fahmikhoirurrijal9427]

Fine addition to my collection

[@TheJowelz]

Thank you for your efforts ! It is highly appreciated you really helped me a lot too !

[@dmadmarinemammalsresearcha3966]

You are welcome! Really glad they helped!

[@valentinadesantis5402]

Thank you so much Tim and DMAD Team! I have followed both first and second course and I found it as a very nice initiative during COVID-19 period. Personally, I have found these two courses very helpfull and I learn something new. Since the first course it's very basic I enjoyed much more the second one and I hope that you will continue with a third course. Good job guys! PS. I had missed the fact that there was a certification at the end of the course. Even better! More points for you! :)

[@dmadmarinemammalsresearcha3966]

Our pleasure! Great to hear!

[@adityakumarsavita3901]

Thank you so much

[@VikasGupta-xg3uv]

Great Video tysm buddy🤝🤝...❤️from India

[@ewanharris5433]

Great

[@ewanharris5433]

Do continue to more advanced analysis

[@abdoulieb.jallow996]

Thank you very much for sharing the lectures with everyone. i could not find episode 18-20. Are they not available or you skipped to episode 20 ? Thank you once more for educating people like me for free. Keep educating. I hope the the course will continue ?

[@dmadmarinemammalsresearcha3966]

Hi Abdoulie, thank you for you kind words. Episode 18 can be found here: kzbin.info/www/bejne/o5izoJ2rbNybapI and episode 19: kzbin.info/www/bejne/n2nFiGalhM-LidE. The course carries onto QGIS 3 but unfortunately there are only 7 or 8 episodes because after that we had to concentrate on keeping our NGO running during this difficult period.

[@alanasalvador2399]

Hi, thank you for another great video! When i try to do the IDW interpolation, I select the extent to include MNE and it brings my output raster size to 99999 and when i manually change it to 50 like in the video, nothing happens when i run it.

[@ewanharris5433]

Hi Tim - Thanks for the series - What is the email to submit for certification, please. Regards

[@ananditajamwal8530]

How can i round off my interpolated temperature values?

[@amolrupakheti7828]

Thank you for your video. How do I extract the values at the set of points that I want?

[@timawbery7397]

Hi Amol, Open the processing toolbox (Processing -> Toolbox). Then type sample raster values and add your points layer and raster layer. Hope this helps!

[@Marisacostawr]

Hi Tim. The temperature layer shows up in a complete different place than my montenegro layer area. Both the project and the montenegro layer are in the CRS UTM 34N. I tried the Temp without changing the CRS and also changing it the project CRS but it still won't work. Any thoughts?

[@dmadmarinemammalsresearcha3966]

Hi Marisa, this is a little difficult to diagnose remotely. Did you set the CRS when you imported the temperature layer? Or did you import it as WGS84 and then project it?

[@ricardoperez2490]

Hello Marisa, i figured it out. For some reason, the first field has no name on the tile and the field 'min' took its place, not as 'field1' as in the video. So the best option you have is to open the csv and put a name on the title of the first column, otherwise it will be confusing. It worked for me

[@anujawasthi8090]

I was following the step by step process of IDW, but I wasn't able to cover the whole extent, can you kindly help me out in this?

[@dianaramirez3508]

Hi, I have a temperature dataset in 2 files (.cvs and .xlsx) and I would like to create a geo-referenced map with multiple layers according to the temperature at different time points. I would like to be able to filter by layer and also select one or more combinations. Is this possible? Any advice is appreciated. Thanks in advance for your help!

[@dmadmarinemammalsresearcha3966]

Hi Diana, the way in which you proceed is going to be mainly based on your dataset. If you have coordinates already then this is very easy. You can just use the symbology to categorise by date (or time) and then you will be able to turn sublayers on and off at your will. If you have multiple temperature variables (e.g. sea surface temperature and air temperature) then it may be worth splitting your data file by temperature type. You can either do this manually in Excel/notepad or you can go to Vector -> Data Management Tools -> Split Vector Layers and split it by your type column. Hope this helps!

[@dianaramirez3508]

@@dmadmarinemammalsresearcha3966 Thank you so much. I have a file with temperatures and coordinates from weather stations at 10 minutes interval time over the next 4 hours, the temperature in centigrade. I need to make a layer from every time interval from set weather stations. If I want to show the combinations of all layers or by layer between them to get two or maybe three final layers. Can I start by splitting data file by time interval? is this the first step? I read about raster interpolation to create a surface of points that are very close. Thanks in advance for your help!

[@timawbery7397]

@@dianaramirez3508 Hi, obviously we don't know your individual project but to us that would seem a sensible place to start. The interpolation you're referring to do is discussed in the above video. Regards, DMAD

[@AlejandroArjona87]

THAAAAANKS man!!!!! I am working in points prediction. someone is working on same?