ASSESSMENT OF LIDAR AND DIGITAL CAMERA DATA IN THE CONTEXT OF
RAPID CHANGE DETECTION METHODOLOGIES
F. Savopol and C. Armenakis
Centre for Topographic Information, Geomatics Canada, Natural resources Canada
615 Booth treet, Ottawa, Ontario, Canada, K1A OE9
fsavopol@NRCan.gc.ca and armenaki@NRCan.ge.ca
Commission IV, WG IV/7
KEY WORDS: LIDAR, DEM/DTM, Multisensor, Change Detection
ABSTRACT:
Emergency mapping is one of the areas studied by the Centre of Topographic Information within the Emergency Mapping project of
the Natural Hazards and Emergency Response Program of the Earth Science Sector, Natural Resources Canada. Rapid mapping,
detection, and monitoring of the landscape changes are significant operations in an emergency mapping response program. Quick
data acquisition using LIDAR technology, also known as laser altimetry, is a rapid way to generate dense accurate DEM of the
topography and the various structures. The overall objective of the present work is to test and evaluate the acquisition, processing
and handling of LIDAR DEM data collected simultaneously with optical data. This includes also the use of the intensity image
captured by the LIDAR system as well as indicative examples for features extraction. LIDAR and digital camera data, airborne GPS
and GPS field control were acquired for an area of approximately 5 square kilometers along a railway and watercourse in the Ottawa
region. Additionally, independent GPS kinematic field survey where more than 300 points were collected as independent
checkpoints. The Lidar data (direct measured DEM data and intensity) were evaluated towards optical (photogrammetric) data and
the ground GPS measurements. The comparison analysis among the various datasets (e.g., LIDAR and photogrammetric DTM,
LIDAR and GPS check points, LIDAR and GIS vector data) was performed using different approaches as point to point comparison,
point vs surface, profile vs profile, surface (shape) vs shape, considering as well the in-flight GPS measurements and attitude data
derived from inertial measurements. The potential of LIDAR data in contributing towards feature extraction and data visualization is
also presented.
1. INTRODUCTION
1.1 Context of the present work
detection system with possible application for emergency
mapping.
The aim is to use existing (before the event) and current (after
the event) geo-spatial data and to produce change information
for the updating of the geo-databases and for monitoring and
tracking the type and rate of the landscape changes.
Current mapping applications such as generation of topographic
information and geospatial database updating, require the
implementation of rapid and economic processes due to the
limitations in the available resources. Canada is no exemption
to this, especially due to its vast territory and its aged National 2. ABOUT LIDAR
Topographic Data Base (NTDB). Various approaches were
investigated at the Centre of Topographic (CTI) for the rapid
change detection using imagery (raster) vs vector data
comparison. The work focuses on the elaboration of tools for
the automatic or semiautomatic extraction of topographic
features from satellite imagery and the simultaneous change
detection. Good results were obtained for the updating of lakes,
the predominant topographic feature in the North of Canada
(Armenakis et al, 2002, Armenakis et al. 2003, Armenakis and
Savopol 2004)
In addition to their utility for current mapping operation, the
change detection tools are even more critical for emergency
mapping. Indeed, rapid detection, monitoring and tracking of
landscape changes are essential tools for an emergency mapping
response situation as the quick acquisition of new geospatial
data, including DEM and digital imagery. The LIDAR, also
known as laser altimetry is a rapid way to generate dense
accurate DSM / DEM of the topography and the various
structures. The use of the returned intensity signal and the
addition of an imaging sensor (digital camera) could increase
the utility of such a system.
The overall objective of the present work is to test and evaluate
the acquisition, processing and handling of LIDAR data
collected simultaneously with optical data and the extraction of
urban and sub-urban features required for a rapid change
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2.1 General use of LIDAR systems
The airborne laser scanning technology (Wehr and Lohr, 1999;
Baltsavias, 1999a) also known as laser altimetry emerged in the
last years as a leading technique for rapid collection of high
accuracy, high density DEM. To be more precise, an airbome
laser scanning system will produce a Digital Surface Model
(DSM) and a Digital Elevation Model (DEM) can be derived
using specific data process methods. The most common name
for this technique was “airborne laser scanning” but in the last
years the name of “LIDAR” from ‘Light Detection And
Ranging’ became more popular. Same users prefer the spelling
“LIDAR”. Another name used is “Laser Range Finder” or
“LRF” (Axelsson, 1999).
The LIDAR technology exists for at least two decades but in the
last several years we see its wide use in topographic mapping
because of the rapid, very precise generation of dense terrain
elevation data. An extensive comparison between
Photogrammetry and LIDAR mapping is given by (Baltsavias,
1999b).
LIDAR is used by diverse sciences sectors that were used to
have their own, specific (non cartographic) measuring
techniques. Such examples are: :
- Detection and measure of individual trees (Persson et al, 2002)
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