# SMS:Boundary Triangles

The perimeter of the mesh resulting from the triangulation process corresponds to the convex hull of the data points. This may result in some long thin triangles or "slivers" on the perimeter of the triangulated region.

## Select Thin Triangles

There are several ways to select and delete long thin triangles.

Long thin triangles on the perimeter of the mesh can be automatically selected using the **Select Thin Triangles** item from the mesh *Elements* menu or scatter *Triangles* menu. The triangles on the outer boundary are checked first and if the aspect ratio of a triangle is less than a critical value, the triangle is selected and the triangles adjacent to the triangle are then checked. The process continues inward until none of the adjacent triangles violate the minimum aspect ratio.

The "drag line" method for selecting elements was designed specifically for this purpose. Elements can be selected with a line by selecting the **Select Elements** tool, holding down the *CTRL* key, and dragging a line through all of the elements to be selected. The selected elements can then be deleted.

SMS makes use of an aspect ratio to determine which triangles to select. Triangles with an aspect ratio below a specified value will be selected when the **Select Thin Triangles** command is used. The aspect ratio value can be changed in the *Element Options* dialog or the *Scatter Options* dialog.

## Related Links

SMS – Surface-water Modeling System | ||
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Modules: | 1D Grid • Cartesian Grid • Curvilinear Grid • GIS • Map • Mesh • Particle • Quadtree • Raster • Scatter • UGrid | |

General Models: | 3D Structure • FVCOM • Generic • PTM | |

Coastal Models: | ADCIRC • BOUSS-2D • CGWAVE • CMS-Flow • CMS-Wave • GenCade • STWAVE • WAM | |

Riverine/Estuarine Models: | AdH • HEC-RAS • HYDRO AS-2D • RMA2 • RMA4 • SRH-2D • TUFLOW • TUFLOW FV | |

Aquaveo • SMS Tutorials • SMS Workflows |