Quadtree and Sub-Grid Sampling FAQ: Difference between revisions

In non-SGS models, the "SX'''L'''" option is often used to lower the pit ground level to improve flow capture. However, an SGS model creates an evaluation-storage relationship based on underlying DEM and is naturally better at capturing flows at pit inlets. Therefore "SX'''L'''" option is not necessary in an SGS model if the DEM inis fine enough. On the other hand, users may receive "ERROR 1278 - Pit <pit ID> inlet level is below lowest channel/pipe bed." after converting a working non-SGS model to an SGS model. Since the lowest elevation sampled inside a cell is used as the “pit inlet level”, an SGS model might picked up an elevation lower than the pipe invert level. In such case, the "US_Invert" attribute of the 1d_nwk GIS layer can be used to manually specify the ground elevation of the pit.