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N4ce Designer
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DTM Factoring and Trending
Boreholes are taken to determine the levels of underlying surfaces, such as bedrock. If sufficient locations are established, a good indication of trends can be established. However, where these are sparse the question arises as to how these surfaces behave between these Boreholes. It has been shown that these underlying surfaces approximate the shape of the free ground surface.
By using a combination of the original ground surface Model and the depths at the Boreholes, a good approximation to the underlying surface can be established. This is called Addition or Subtraction.
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Factoring is used either to predict the height of a reinstatement surface or to add sufficient depth so that after settlement the surface profiles are as predicted. A height difference between two surfaces is determined and a percentage of this height difference added to or taken away from the DTM to obtain the final surface profile.
An option, called Surcharge allows the vertical movement of a Model, with updates to any height annotation associated with the Model points. This is equivalent to changing the datum level of a Model. |
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A feature has been introduced to the Designer Edition that allows a Trend Surface to be generated from selected points. This is a least squares, Best-Fit Plane created from points in a Select List. Once determined this Trend Surface can be used to calculate the heights of new points. An Insert Points option allows selection of Trend Reference from any DTM.
The trend surface can be added to the 3D viewer as shown opposite. |
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In some situations, especially in geological applications, you may need to create new surfaces perpendicular to the current surface.
An option has been provided in the New model creation, called Perp Offset that creates points at the centre of each triangle of an existing DTM, along its vector normal at a nominated distance. |
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