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not every zpt lowered using Z Shape layer

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I'm having some problems using a Z Shape layer where not all the zpts have been correctly lowered. In my Z Shape layer I have a line with elevations snapped at each end, the option is set to MIN and the shape width is 10 (smaller than my grid size which means a thin line is produced). This seems to have worked at first glance, however I noticed water backing up in the model and so have had a look at the check files.

The sh_obj_check file shows the line which should be lowered as I expected, however looking at the aztual zpts there is one point which has not been altered. This isnt because it is already low enough. In the attached picture this can be clearly seen circled in red - the thin blue line is the line in my Z Shape layer, the black dashed line is the sh_obj_check layer and the yellow triangles are the zsh_zpt_check layer.

Does anyone know why this has happened?

Any suggestions would be most welcome.

Thanks in advance



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Hi Gillian,

I'm not 100% on this but in Appendix C4 of the manual it says that the modified z points for a GULLY z-line (same as MIN) are not output to the _zpt check file, so it may be the same for a z-shape. I think generally you should have at least a cell width modified when using the MIN option (if you're trying to model a ditch or similar), as you'd want to make sure the ZC point is lowered and not just cell sides.

Hope that is of some help



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Hi Gillian/Richard

1. To clarify your point Richard, for the Gully or Min option using Z Shapes the changed Zpts are reported in the 2d_zsh_zpt_check layer, however, if using the (old) Read MI Z Lines == command Min/Gully Zpt changes are not reported.

2. Gillian, which TUFLOW build are you using? We're not aware of any problems with Z Shapes in the latest build, so if you're not using the latest 2009-07 build can you please try this one. If the problem still occurs can you please email through to support@tuflow.com the following text and mif/mid files: .tcf, .tgc, any MI Projection layer, 2d_zsh layer and any 2d_loc layer. The 2d_zsh_zpt_check layer would also be good edited with a circle added around the offending point so that we can easily find it.



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