Technology Highlight: GIS Programming Breakline Check By Jeff Kuran, Krishna Kumar, Anantha Subramaniam, Vinod Kazhipurath, and Paulson Tharakan. Revision & Quality Control Section - Mapping & Positioning Services - CGIS The DEM is composed of: Mass Points: A regular grid of heighted points Special Points: Single heighted points of special significance (e.g. tops of hills) Breaklines: Lines of heighted points that represent a seam along which there is an abrupt change in terrain slope In order to verify that breaklines compiled actually represented abrupt changes in slope, a triangular irregular network (TIN) was generated, and the slope of the triangles on either side were compared. ARC/INFO's "TINARC" command (with the "LINE" option) provides the maximum slope for each of the triangles. However, we did not want to compare the maximum slopes, we wanted to compare the slopes perpendicular to the breakline. The following algorithm provides the slope comparison we required.                 CONTENTS NEXT