Economic value raster not assigning correct values to pixels

NatCap Software Support
#1

Hello,

I am using the InVEST Carbon Model and I am not understanding why the sum of the npv_fut.tiff pixels is giving me a different economic value as when I apply the formula suggested in the documentation myself.

I am using a 37 USD as Price of Carbon and 0 as Annual Rate and Market Discount.

I have an amount of 24,697 Mg of C sequestered between current and future scenario (30 years).
(The delta_cur_fut raster gives me back this result which is correct)

Applying the formula suggested in the documentation I should have $913,819.34 USD as economic value. But in the report as well as when I sum up all the pixel values in the npv_fut.tiff I am getting $30,460.64.

Could anybody explain why this is happening?

Thank you very much!

#2

Hi @pcastro,
Thanks for pointing this out! This is indeed a bug in the model where when both the annual rate and market discount are 0, the value is off by a factor of the number of years. We are fixing this now and I’ll send you an updated version with the bug fixed.

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#3

Thank you very much, I really appreciate it!

#4

Hi @pcastro,
Thanks for your patience! We’ve fixed the bug and you should now be able to use it with both rates set to 0. Here’s the windows installer: https://storage.googleapis.com/releases.naturalcapitalproject.org/invest/3.9.0.post202+g6c1a017d/InVEST_3.9.0.post202+g6c1a017d_x64_Setup.exe and the mac installer: https://storage.googleapis.com/releases.naturalcapitalproject.org/invest/3.9.0.post202+g6c1a017d/InVEST_3.9.0.post202+g6c1a017d.dmg

Note that I’d expect the correct value for your case to be $913,789.00, not $913,819.34:

24,697Mg * 37$/Mg / 30 * sum from 0 to 29 (1) =
24,697Mg * 37$/Mg / 30 * 30 =
24,697Mg * 37$/Mg = $913,789.00

Let me know if that works for you!

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