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A maps operation is an overlay containing the result of an operation between several overlays. These overlays can contain Grid type maps, but also untyped grids and polygons.

This interface is accessed by clicking on the in the section Renderings of the Simu - Renderings tab in the MithraSIG ribbon.

Operation

•Sum: Logarithmic addition of maps A and B. The formula is of the type 10 * Log(10 ^ (A/10) + 10 ^ (B/10)).

•Weighted sum: Logarithmic addition of maps with weights and penalties. The formula is of the type 10 * Log((wA/ (wA + wB)) * 10 ^ (A + pA/10) + (wB / (wA + wB)) * 10 ^ ((B + pB)/10)) where wA and wB are the weights of maps A and B, and pA and pB are the penalties applied to those maps.

•Subtraction: Subtraction of maps A and B. The formula is of the type A - B.

•Maximum: Maximum of maps A and B. The formula is of the type MAX(A,B).

•Addition of a constant: Adding a single value (ambient noise for example) to map A values. The formula is of the type 10 * Log(10 ^ (A / 10) + 10 ^ (Constante / 10))

Maps

Liste des cartes servant de source à l'opération entre cartes. En fonction de l'opération choisie, une ou plusieurs cartes peuvent être utilisées.

Les calques servant de source peuvent être des cartes, des calques contenant des grilles non typées ou des calques contenant des polygones non typés.

Lorsqu'un calque contenant des polygones est utilisé, il convient de sélectionner l'attribut à utiliser pour faire les opérations. Pour une grille, les valeurs z des pixels sont lues pour les opérations.

Formula overview

A preview of the formula used for the operation is shown in this section.

Result

•Theme: indicates which theme has to be applied to the result grids. There are three modes for the theme:

oAutomatic: a new theme is automatically created from the computed minimal and maximal values.

oNone: No theme is applied to the new grid.

oExisting: the user chooses an existing theme from the list. The button can be used to delete a theme. This button cannot be accessed if the current theme is a default theme. The button can be used to edit a theme or simply to view a them in the case of a default theme (see Theme parameters).

•Resolution: corresponds to the size that a pixel represents. A resolution of 5m means that 1 pixel = 5 meters.

•File name/overlay: name of the overlay created containing result grids.