What would cause the NDR model to have negative values? I’m using a 0.1 for subsurface % and length of 50. For this particular application I’m looking to estimate N export from our upland areas - it’s the coastal areas that have no N load that are showing negative values. Does this mean that they …

Thanks Dave. We will try that certainly ! Appreciate the feedback. I will get our project cooperator who is doing the LULCs to take a look at this ASAP. I will let you know how we made out once he is done and we have tried the SDR model runs again with that nodata changes you have suggested made. T…

Hi Dave. We filled the nodata holes with the appropriate raster cell values and re-tried the SDR model. We still have negative values in the sed_exp and other outputs, If you have any further suggestion, it would be appreciated. Thank you. Gordon user: BVIB

Hi Gordon, thanks for the update. I assume you mean you still have negative values in the “scenario - baseline” change raster? If so I would compare the two LULCs and confirm that the new crop pixels in the scenario are actually replacing higher retention landcover types. Glancing at the subset of d…

Thanks Dave. I am taking a look at it. Appreciated

Hi Dave: the bare ground and urban pixels converted to crop are only 0.2 % of the total watershed area and they are not spatially distributed across all of the watershed area… as our negative values in the “scenario - baseline” change raster are. I will work it it some more. Thanks for the suggesti…

Hi @BVIB , the SDR maintainer has graciously weighed in and provided the following feedback after looking at the DEM you shared earlier in this thread. that dem is a 1m resolution. that’s way too small for what the SDR science is derived from. having 1m resolution doesn’t get you a better result …

Thanks Dave ! The info and advice is greatly appreciated. Thanks to you and to your SDR maintainer for taking the time to look at it for us. We will follow your advice. Appreciated. Gordon (for a project in NB) user: BVIB

Hello Following up on suggestions that you and a few other InVEST / ROOT people have made to us, we have now made some additional pretreatment to our data to attempt to eliminate some of difficulties we had with the negative values in our scenario change rasters. These input data pretreatments cons…

Hi Gordon, sounds like you’ve made some good progress. All that pre-processing sounds very smart and worth doing. FYI that second step of aligning extents and matching pixel sizes is actually something that’s always done by the invest model, usually using the DEM as the one to match all others to. B…

Negative Values in n_export for NDR model?

Software Support

JIahengDu June 7, 2021, 10:38am 29

I am facing the same question, are you figure it out??

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Negative Values in n_export for NDR model?

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