Create sections with multiple DTMs

You can use this function to extract cross sections from DTMs that have been created using the Create DTM function. The sections to be extracted are defined by using a cross-section axis and the spacing along the axis. The sections are taken along the axis length, at the interval defined by the spacing value.

To run this function: Choose Surfaces > DTM file functions > Create sections with multiple DTMs, or...

In the Function Chooser, type SECTION MULTIPLE DTMS, and press ENTER.

The coordinates that define the start and end positions for the axis are found in the axis record of the string file associated with the first DTM. If these coordinates are incorrect or do not exist, you can enter coordinates for the axis in the input fields.

You select DTMs on the Multiple DTM sections form in order of decreasing elevation. Sections can be taken as closed (using a pair of DTMs, a top and a bottom) or open (using a single DTM).

You can use a boundary string to constrain the sections that are produced. The boundary string can consist of multiple closed segments. For closed sections, the boundary string for the "top" DTM is used for both sections.

Fields on the Multiple DTM sections form

Field	Description
DTM Specifications
DTM Location	The name and location of the DTM you want to section.
Object ID	The object number of the DTM you want to section.
Object name	The object name of the DTM you want to section.
Trisolation ID	The trisolation number of the DTM you want to section.
Trisolation name	The trisolation name of the DTM you want to section.
Section type	Open: Each successive DTM is used alone to extract open sections. Closed: Each successive DTM is treated as the "top" DTM, and the following DTM as the "bottom" DTM, during processing. The last identified DTM in the list, which does not have a following DTM, is processed as open.
Include	Selected: The DTM is used as both a "bottom" and a "top" DTM. Cleared: The DTM is used as a "bottom" DTM but not as a "top" DTM. If you select this option for DTMs that represent the bottom of an ore band before a waste area, a section is not created for the waste between the ore bands.
Boundary location	The name and location of the boundary string file.
ID	The ID number of the boundary string file.
String	The string number of the boundary string, in the boundary string file. Note: The boundary string can consist of any number of nested segments. The direction of these segments (clockwise or anticlockwise) is not important. Imagine that you are viewing a surface along the normal to the plane used during surface creation (that is, looking directly at the plane), the rules for clipping are: For a single segment string, "inside" the segment refers to triangles physically inside the segment. For a string with a single level of nested segments, "inside" refers to triangles physically inside the outermost segment but outside any inner segments. Multiple levels of nesting are handled by alternating "inside" and "outside" for each level of nesting. For example, if the black lines are segments of a string, the red areas are considered "inside" the string and the white areas are "outside":
Define files to create
Location	The name and location for the string file created.
Section	By interval: Sections are taken at regular intervals along the axis line, with the distance between sections defined by the value in the Section values field. By range: Sections are taken at the locations along the axis line as defined by the range in the Section values field.
Section values	The range of values along the axis line at which the sections are created.
Define axis coordinates
X	The X coordinates of the first and last points of the axis line.
Y	The Y coordinates of the first and last points of the axis line.
Z	The Z coordinates of the first and last points of the axis line. Note: If the plane used to create the DTM is horizontal, only the X,Y coordinates of the axis line are required. For other orientations, the Z coordinate is also required.
Section orientation is	Perpendicular to the axis: The sections are taken at a right angle to the axis line. Parallel to the axis: The sections are taken on the same orientation as the axis line.

Output

A string file is created, which contains strings in different views depending on the orientation of the axis file. You can switch the coordinate data fields around using STRING MATHS to change them to plan view, or to transform them to real world coordinates if the axis was oblique.

When sectioning surfaces created on non-horizontal planes, the process is:

The axis line is projected onto the plane.
The surface and axis line are transformed so that the plane and axis line are horizontal.
The section extraction process proceeds as for a horizontal plane surface.

Trouble Shooting

Message	Description
`The selected were not created on the same plane.`	The DTMs used must be created on the same plane. Choose different DTMs and recreate the DTMs on the same plane, or transform the data in one of the DTMs to match the plane of the other.

You can use this function with clipped DTMs. However, this function might run more slowly if either of the clipped DTMs has a boundary that is concave in nature, for example:

You will get a faster result if you use unclipped DTMs and nominate their boundary strings in this function.