In this section, an automatic size assignment is set taking into account a given maximum allowed chordal error. Note that using this options GiD will use the mean curvature of each entity in order to assign a mesh size to it. This size will be the same for the whole entity, so if there is a surface with zones with very different curvature, the mesh should not be adapted locally inside the entity.

• Select Mesh->Unstructured->Sizes by chordal error…
• The following window appears

• Enter 0.05 as chordal error. This error is the maximum distance between the element generated and the real object (geometry).
• Enter 4 as maximum meshing size.
• Enter 0.1 as minimum meshing size.
• If the right bottom button is clicked some extra information appears. We can select a curved line and see how the mesh will look like in this line. Click on the button "line" icon and select the line 34 and change the chordal error value in order to see how the mesh would change.
• Press OK.
• To see the sizes that GiD has assigned automatically, you can select the Draw->Sizes->All types option in the Mesh menu.
• Generate the mesh with the same general mesh size.
• The resulting mesh has a high concentration of elements in curved areas. Now our approximation is significantly improved.

Note than the minimum or maximum mesh size is not a limit of the possible sizes of the elements to be generated, it is only a limit of the 'assigned wished sizes' (a line shorter than this minimum size will generate a short element)