Mountain Cartography

Orienteering maps

3603.1 - Semi-Automatic Extraction of Near-Ground Vegetation from LiDAR Data as Base for Orienteering Maps

Monday, July 3
2:50 PM - 3:10 PM
Location: Virginia A

LiDAR delivers a three-dimensional point cloud with a huge amount of data. The challenge is to gain the relevant information from this geodata about the vegetation for developing an orienteering base map.
An orienteering map is a detailed topographic map that contains additional information about the runnability of the terrain. In order to maintain equal opportunity in competitions worldwide, orienteering maps are standardized by the International Specification for Orienteering Maps (ISOM) of the International Orienteering Federation IOF. In the mapping of the vegetation, ISOM distinguishes between undergrowth and areas with dense trees or thicket. This information about the runnability is very important for the competitors so they can plan and run their chosen route between the control points. If the competitor comes upon a vegetation area that is not mapped or incorrectly mapped it may negatively affect their competition time. This violates the principle of equal opportunity.

LiDAR data has been successfully used as a base for orienteering maps for more than 10 years. From the calculated terrain model, the contour lines are created and then generalized through field work. However small relevant information for the competitor must be emphasized so that they are clearly visible on the printed map.
In addition, point, line and area objects can be extracted from the hill shading using visual interpretation. Examples of these are paths, streams or erosion gullies. This information must be classified and verified in the terrain.

This work deals with the analysis of near-ground vegetation in the forest. "Near-ground" refers in this work to the zone between the ground and 3m above ground. The orienteer moves in this zone. The correct representation of the vegetation according to the ISOM is still a great time factor for the orienteering mapper, especially in the forests of the Swiss Midlands. These forests are characterized by many small vegetation areas which must be mapped or generalized individually. More detailed, classified and localized vegetation base mapping helps the orienteering mapper during field work and therefore saves time.

In LiDAR, the technological progress is from "First and Last-Pulse" to "Full Waveform". In the case of «First and Last-Pulse», the laser scanner detects the tree canopy as the first pulse and the forest ground as a second pulse in a wooded area. On the other hand, the entire received signal is stored and further processed in "Full Waveform". Thus "Full Waveform" provides additional points between the forest ground and the tree canopy. Point clouds from the “Full Waveform” data are very useful for ground-level vegetation mapping.

This work shows that the cartographer is able to interactively adjust various parameters for a small relevant training area so that the calculated vegetation map corresponds as precisely as possible to the reality on the terrain. The vegetation is classified according to ISOM. For each LiDAR point the 3D coordinate, the classification and the intensity of the returned laser pulse are used. These selected parameters depend on the forest structure, the point density of the LiDAR data, and the time of flight. A flight before leaves on provides the best information about the near-ground vegetation in the forest. The determined parameters for the training area can then be applied over the entire map area and automatically creates the vegetation base map.

Based on this work, a new module for the interactive preparation of the base map for vegetation mapping from LiDAR data was developed in the cartography software OCAD. This module allows a new, interactive analysis of the vegetation and provides the cartographer with a better vegetation base map for the mapping in the terrain.

Gianreto Schaad

Software Engineer
OCAD AG

Gianreto Schaad is a software engineer by OCAD AG, Switzerland. The company develops the cartography software OCAD.
He graduated from the University of Applied Sciences Northwestern Switzerland FHNW in Geomatics and in Computer Science.
He is UNIGIS Msc student at University of Salzburg, Austria and is writing a Master Thesis about "Semi-Automatic Extraction of Near-Ground Vegetation from LiDAR Data as Base for Orienteering Maps".

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Georg Gartner

Full Professor, Head of Research Group Cartography
Vienna University of Technology

Georg Gartner is full professor and head of the research group cartography at the department for geoinformation and geodesy at the Vienna University of Technology. He is past president of the ICA and editor of the book series "Lecture Notes on Geoinformation and Cartography" as well as editor-in-chief of the "Journal on Location-based Services".

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