Comments on: The Need for Breaklines http://lidarnews.com/the-need-for-breaklines Laser Scanning Industry News Fri, 30 Jul 2010 13:46:54 +0000 hourly 1 http://wordpress.org/?v=3.0 By: Harold Rempel http://lidarnews.com/the-need-for-breaklines#comment-365 Harold Rempel Tue, 07 Jul 2009 13:00:54 +0000 http://lidarnews.com/?p=1109#comment-365 I actually remember working on this project in the screenshot. I worked for Fugro EarthData at the time. It is (roughly) from about 2003-2004 where we processed LiDAR and aerial photography over Mecklenburg County, NC. We ran several tests and found that the only way to get the contours to "behave" properly while crossing the highway was to introduce breaklines. No matter how dense the lidar is, it is still point data which never completely defines an "edge". To answer your question; NO, we should no longer be delivering contours from LiDAR given the methods available now to visualize terrain. Some of us have been arguing this point with customers for years now. The problem is that the culture has been slow to change. Maybe the solution is to start winning over minds in academia. Or maybe this problem will correct itself as the generation raised on contours begins to retire. Either way, it has been a matter of frustration since we know that contours from LiDAR seem to be a waste of time and resources when the LiDAR can yield such an accurate surface. Breaklines may still be needed in some cases to "correct" a surface such as in places where a retaining wall (for instance) affects the terrain. Gridding - Agree here as well - When you are forced to deliver contours from LiDAR, gridding the source data is practically a necessity in order to reduce the number of isolations and to "smooth" the appearance of the contours. I actually remember working on this project in the screenshot. I worked for Fugro EarthData at the time. It is (roughly) from about 2003-2004 where we processed LiDAR and aerial photography over Mecklenburg County, NC. We ran several tests and found that the only way to get the contours to “behave” properly while crossing the highway was to introduce breaklines. No matter how dense the lidar is, it is still point data which never completely defines an “edge”.

To answer your question; NO, we should no longer be delivering contours from LiDAR given the methods available now to visualize terrain. Some of us have been arguing this point with customers for years now. The problem is that the culture has been slow to change. Maybe the solution is to start winning over minds in academia. Or maybe this problem will correct itself as the generation raised on contours begins to retire. Either way, it has been a matter of frustration since we know that contours from LiDAR seem to be a waste of time and resources when the LiDAR can yield such an accurate surface. Breaklines may still be needed in some cases to “correct” a surface such as in places where a retaining wall (for instance) affects the terrain. Gridding – Agree here as well – When you are forced to deliver contours from LiDAR, gridding the source data is practically a necessity in order to reduce the number of isolations and to “smooth” the appearance of the contours.

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