I tried running CSS model for estimating the monetary valuation of carbon sequestration in Goa. The model ran successfully and I have the result. But the issue is with the carbon sequestration.
CSeq (InVEST estimated) is not equal to [ Alternate Carbon Storage - Baseline Carbon Storage]
Attaching a photo of the result and the log file for reference. The same mistake I got for all other states over the years.
PS: I checked the properties of both the maps used, and they are identical.
I have issues with the value of Carbon Sequestration (Change in Carbon Storage)… Baseline Carbon Storage is 15761589.84 and alternate carbon storage is 15683651.29. InVEST estimated Change in carbon storage equal to 923.78. Should not the carbon sequestration be around 77000 (Alternate carbon storage- baseline carbon storage)?
I see that there is a problem with your total sequestration values. So i tried to replicate it with our sample data, and do not see the same problem on either InVEST 3.16.2 or 3.17.1. Would you please try the latest InVEST version and let us know if the incorrect sequestration value still happens? Thanks.
I think that the issue must have to do with the LULC layer GA_10.tif having a line of NoData through the upper part of the study area, where GA_05.tif has valid data:
I’m not exactly sure how the model is processing the carbon storage sum and difference that appears in the HTML window, since i think that it should still calculate the correct difference value, despite this missing data. So i’m going to ask the software team to look into this.
Meanwhile, i suggest filling in the missing line of data in GA_10.tif and see if that helps the results come out as expected. Please let us know if it does.
Yes, it is due to the missing row of data, and these results look correct to me. Baseline carbon storage is calculated as the sum of c_storage_bas_Goa0510.tif. Alternate carbon storage is calculated as the sum of c_storage_alt_Goa0510.tif. Both of these sums are correct.
Change in carbon storage is calculated pixelwise, meaning we take the difference between baseline and alternate carbon on each pixel, and then sum those differences across the whole raster. And so that difference can only be calculated for pixels where both baseline and alternate carbon are defined. Because one of your rasters has a missing row of data, that row does not count towards the total difference.
To put it in mathematical terms,
total baseline carbon storage = \sum_{i\in I} \text{baseline carbon storage}_i
where I is the set of non-nodata pixels in the baseline carbon storage raster
total alternate carbon storage = \sum_{j\in J} \text{alternate carbon storage}_j
where J is the set of non-nodata pixels in the alternate carbon storage raster
total change in carbon storage = \sum_{k\in K} \text{alternate carbon storage}_k - \text{baseline carbon storage}_k
where K is the intersection of I and J
total change in carbon storage \neq \text{total alternate carbon storage} - \text{total baseline carbon storage}
because I \neq K
