Revision as of 10:56, 29 January 2026 view source Emilie Nielsen (talk \| contribs) Administrators 6,278 edits →Enable High-Resolution Output ← Older edit		Revision as of 11:07, 29 January 2026 view source Emilie Nielsen (talk \| contribs) Administrators 6,278 edits →Water Level Interpolation Methods Newer edit →
Line 45: =Water Level Interpolation Methods= Similar to the standard output, the HR output needs to interpolate cell centre water levels to cell corners. However, the interpolation methods for the standard output (<font color="blue"><tt>Map Output Corner Interpolation </tt></font> <font color="red"><tt>== </tt></font> <font color="black"><tt>Method C</tt></font>) can produce "bumpy" HR water level ~~output~~outputs in direct rainfall models with steep terrain, as the water level is linearly interpolated from the cell centres/corners, while the change of sub-grid elevations may not be linear. This often happens between fully wet cells and sheet flow cells, as illustrated below. [[File:corner_h_intp_output.png\|480px]] In the HR water level output, these locations often have high water level with triangular shape. [[File:HR_Intp_A.png\|480px]]<br> '''Method A HR Interpolation Approach ~~== Method A~~''' (~~Gray~~gray lines show the triangulation TINs) Two additional methods have been added for the HR corner water level interpolation: Line 62 ⟶ 66: * Method C is the default option that applies the same sheet flow checks as the Method B. In addition, it also uses the number of wet SGS sampled points as a weighting that biases non-sheet flow cells that further improves the mapping to in-stream water levels. The two images below present the high-resolution water level output at the same location, but with <tt><font color=blue>HR Interpolation Approach </font><font color=red>==</font> Method B</tt> and ~~Method C~~<tt>MethodC</tt>. As can be seen, the water level along the narrow stream is “smoother”. [[File:HR_Intp_B.png\|480px]] [[File:HR_Intp_C.png\|480px]]<br> '''~~HR Interpolation Approach ==~~ Method B (left) and Method C (right) HR Interpolation Approach''' Note that when these two methods are applied, the interpolated corner water level is biased to the non-sheet flow cells, and consequently, sheet flow cells may appear as “dry” cells. The improved approach ~~that~~ takes into ~~the~~ account ofthat the sheet flow water level is currently under development. Whilst Methods B and C can substantially improve the water surface mapping of SGS models using direct rainfall (rain-on-grid), there will always be inaccuracies with mapping at a higher resolution than the 2D cell resolution due to interpolation and extrapolation. Regardless of the software, the greater the ratio of 2D cell size to the high-resolution DEM cell size, the greater the potential for mapping inaccuracies. Should better mapping accuracy be required, reducing the 2D cell size to compute the spatial variation in water surface and velocities more accurately is, by far, the best course of action. Please also note that it is not necessary to use these options for non-rainfall on grid models.

TUFLOW HR Output: Difference between revisions