Quadtree and Sub-Grid Sampling FAQ: Difference between revisions
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=How to decide between using SGS, Quadtree and 1D open channel?=
The number of 2D cells across channel is critical. Based on the <u>[https://downloads.tuflow.com/_archive/Australian_Rainfall_Runoff_Project15_TwoDimensional_Modelling_DraftReport.pdf ARR 2D modelling guidelines]</u> the aim is to have 6 cells across the river, creek or drain (if not using SGS). However, use of SGS does allow use of a much fewer cells across a waterway whilst preserving the total conveyance of the waterway. The only downside of SGS is that if the velocity distribution across the waterway, or for example the super-elevation of the water surface around a bend, is important then sufficient number of cells is needed to accurately reproduce the velocity distribution or water level variation. Quadtree grid can be useful for this purpose.
=How can I convert 1D open channel into Quadtree?=
Follow these steps to create a TIN from ESTRY cross section inputs that can be read into a Quadtree model: <br>
# Use the following script that has been developed to convert ESTRY cross sections inputs into 2d_zsh line and points: https://gitlab.com/tuflow-user-group/tuflow/data-pre-processing/estry_to_zsh <br>
# Digitise a 2d_zsh merge polygon around the 2d_zsh lines and points that define the open channel. Tutorial Module 2 provides instructions on how to create this 2d_zsh merge polygon: [[Tutorial_M02#Part_2_-_Other_Topographic_Updates |Tutorial M02 Part2 - Other Topographic Updates]] <br>
# Read the 2d_zsh line and points cross section inputs into the model using the "Read GIS Z Shape" command in the tgc file. <br>
# Read the 2d_zsh merge polygon into the model using the "Create TIN Zpts Write TIN" command in the tgc file. <br>
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