Extreme small value in SDR

Hi, I’m having a problem with my SDR model. The output value is extremely small like 0.0000001 sth.

My R value is around 700-1500, K is around 0.03-0.05, the rest settings should be correct, I tried to change the project system of K and R map but it doesn’t work. What could be the problem?

I also attached the input data if you need.

Best regards,
Hao Chen

InVEST-Sediment-Delivery-Ratio-Model-(SDR)-log-2019-12-04–21_48_56.txt (40.4 KB)

Hi @chn7424814 -

The input spatial data is in a geographic coordinate system, with units in degrees. The model requires that the inputs be in a projected coordinate system, with units in meters. When linear distance calculations are done in the model, it makes a big difference if it is computing with degrees (which are, in your case, very small numbers) or meters. So reproject all of your inputs to the same projected coordinate system (such as UTM), rerun the model and see if that helps.

~ Stacie

Hi @chn7424814 -

Did you actually “reproject raster” (ArcGIS) or “warp” (QGIS) to change the coordinate system? It looks like the coordinate system itself has been set to WGS_1984_UTM_Zone_1N, but the cell size is still 0.0083333333 (for R_map.tif), 0.00051891102 (for Soil_K.tif) etc. I’d advise going back to your original datasets and making sure you use one of these tools to reproject it properly.

~ Stacie

1 Like

Hi, Staice,

Thanks for your patient help, now I changed the coordinate system of all the input map from the original source. The model runs well and gives good results.

Have a good day~

Glad to hear it! Thanks for letting us know.

~ Stacie