referens system avrinningskarta
Hello, sorry I have to write in English.
I am looking into the runoff (avrinning) of several watersheds of lakes I have delineated. I would like to calculate the average (summer) runoff for my watersheds based on your summer avrinnings map from 2005, 2006 and 2017 (https://vattenwebb.smhi.se/avrinningskartor/). When I download I get a .PNG file without coordinate system. Is there a map I can download with coordinate system? Or am I just doing something wrong :\
Thanks for your consideration!
Isolde
I am looking into the runoff (avrinning) of several watersheds of lakes I have delineated. I would like to calculate the average (summer) runoff for my watersheds based on your summer avrinnings map from 2005, 2006 and 2017 (https://vattenwebb.smhi.se/avrinningskartor/). When I download I get a .PNG file without coordinate system. Is there a map I can download with coordinate system? Or am I just doing something wrong :\
Thanks for your consideration!
Isolde
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Hi Isolde!
You are correct in your observation as we only have picture files (.png) of the average runoff. The picture files show Sweden in the projection 'SWEREF 99 TM', so you could perhaps open the picture in your GIS program and make a georeference with two landmarks to a map of Sweden in that same projection. Next step would be to save the .png as a .tiff-file, and then do a 'Raster to polygon' calculation. That should produce a corresponding map.
Another way to get almost the same information would be to download modelled data for the watersheds you are interested in. Given that we at SMHI have delineated the same watersheds of course. Have a look at: https://vattenwebb.smhi.se/modelarea/
Click on the lake or watershed you are interested in and download an Excelfile of modelled data/observations from that watershed.
Open the Excel file:
In the Excel file, under the tab 'Månadsvärden', the mean values for each month is shown. Calculate the total volume of water(in liters) that has left the watershed during the months you are interested in and divide by the area of the watershed(in square meters) and you have the summer rounoff in the unit [mm]. You'll find the area of the water shed under tab 'Områdesinformation'.