I have assigned the elevation and the volume flow to each point at a river (with v.to.db and v.what.rast). Now I want to calculate the Elevation difference between each pair of points and then calculate the Hydropower between them by using P=density * Q * delta_h * g. Here you can see an example of my Attribute Table (I know the differences are too small but it is only an example):

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I don't know how to do this. Is there a way in GRASS or how can I realize that?

OK, I know how to Calculate the Hydropower with given Elevation difference (SQL Builder (Update) -> Field Calculator)). It works fine to multiply different rows. But one step is in my opinion not feasible with that: To Calculate the differences between Elevation as shown above (I cannot say something like: Elevation=i+1 - Elevation=i). Is there another Way?

Maybe to calculate it directly in GRASS and not in the Attribute table?

  • Nobody can tell me? Or is it the wrong way to calculate the Hydropower? – Tim Feb 26 '15 at 10:12
  • Just take this table to excel and calculate the difference - – FelixIP Mar 1 '15 at 4:43

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