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Overlay Options for Structures



Understanding Overlay Options


The Overlay options define how the surface within a structure or area is created. These options are visible in ever 

When no Overlay options are set, a structure will be calculated from the entered boundary point altitudes, so contours and spot elevations are ignored. 

When an Overlay option is selected, the surface of a given structure is produced from contours or spot elevations, and inputted altitudes for that structure may be ignored.


Overlay Options Explained


Surface Option Checked

When Surface is checked, the boundary altitudes entered for a structure are used with any contours or spot elevations. This option gives you precise control over the boundary of a structure, while allowing flexibility within that shape. Selecting only Surface as your Overlay option can be very useful, a good example is if you have a car park with a well-defined perimeter and need to take into account contours or spot elevations for drainage.  


Points Option Checked

When Points is checked, altitudes entered for the structure are ignored in favour of the spot elevations and contours for that plan. Although not as commonly used as the other options, selecting only Points is effective when the altitude of a structure is otherwise unknown. 


Surface and Points Options Checked

If you have both Surface and Points selected in the Overlay options, your structure will be created using contours and spot elevations. Your structure will also ignore the boundary altitudes. Checking both Surface and Points is useful especially if, for example, there are different landscaping areas. 


Note: Using Overlay options will increase calculation time.