![]() ![]() ![]() The distinguishing geometric characteristic of a Delaunay triangulation is that a circle surrounding each triangle side does not contain any other vertex. One approach is called Delaunay Triangulation which, in one of its constrained forms, is useful for representing terrain surfaces. 1199SEIU AARP Adventist Health Aetna Anthem Blue Cross Blue Cross Blue Shield of Alabama Blue. (There are algorithms for triangulating irregular arrays that produce unique solutions. Trusted Contouring Specialist serving Takoma Park, MD. Similarly, the smaller the contour interval you intend to use, the more spot elevations you need. In general, the density of spot elevations should be greater where terrain elevations vary greatly, and sparser where the terrain varies subtly. Related to this element of subjectivity is the fact that the fidelity of a contour map depends in large part on the distribution of spot elevations on which it is based. As you will see, deciding which spot elevations are "near neighbors" and which are not is subjective in some cases. You may notice that there is more than one correct way to draw the TIN. I omitted breaklines from this example just to make a point. ![]() Photogrammetrists refer to spot elevations collected along linear features as breaklines (Maune, 2007). contour interval The difference in elevation between two contours.2 cross section The representation of a landform as it would appear if cut by an intersecting plane. In practice, spot elevations would always be measured at several points along the stream, and along ridges as well. berm The continuous artificial contouring of a slope or water- channel bank.1 contour An imaginary line on the surface of the earth connecting points of the same elevation. Wonder why I suggest that you not let triangle sides that make up the TIN cross the stream? Well, if you did, the stream would appear to run along the side of a hill, instead of down a valley as it should. With a little imagination and practice, you can visualize the underlying surface from the TIN even without drawing contours. (Spot elevations produced photogrammetrically are called mass points.) A useful characteristic of TINs is that each triangular facet has a single slope degree and direction. The vertices of the triangles are spot elevations that may have been measured in the field by leveling, or in a photogrammetrist's workshop with a stereoplotter, or by other means. Essentially, any plastic surgery that changes the shape of one or more body parts is considered body contouring. A TIN is a vector representation of a continuous surface that consists entirely of triangular facets. Body contouring is a conglomerate of cosmetic surgery procedures. The result is a triangulated irregular network (TIN). ![]()
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