UNDERSTANDING LIDARLIGHT DETECTION AND RANGING

• LIDAR is a remote sensing technique that can measure the distance to objects on and above the ground surface by illuminating the targets with a laser light and analyzing the backscattered light.

• LIDAR produces High accurate x,y,z measurements

TYPES OF LIDAR • AirborneAirplanes and helicopters are used to acquire data over broad areas. The majority of these platforms cover about 50 kilometers per hour with a high accuracy level. Airborne LIDAR systems are the most commonly used for generating DEM (Digital Elevation Models). • Ground basedOffers a street perspective and can be mounted in cars, boats, trucks, tripods or trains. Is great for smaller areas where higher density is required.

IMPORTANT THINGS TO KNOW ABOUT LIDAR

• Point spacing of your LIDAR Data Refers to how close the laser points are to each other. This is important because the point spacing determines the resolution of derived products. If you want to create building footprints you need at least 1 meter spacing. • Type of files supply with your LIDAR LAS files or ASCII Intensity images Raster files (DEM) Metadata• QA and QC of your data Completeness of data (LAS files, intensity images, etc) Comparison of elevations among different deliverables• Classification of your data. How many classes does your LAS point data contain? Every point of your LIDAR has a classification assigned to it that defines the type of object and its correspondent reflected laser pulse. These classifications are defined using numeric integer codes.

IMPORTANT THINGS TO KNOW ABOUT LIDAR

The SC Consortium Project uses the following classification:

The ESRI LAS 1.1 standard use this classification:

IMPORTANT THINGS TO KNOW ABOUT LIDAR

• Understanding Returns The laser pulse emitted from a LIDAR system reflects from objects on and above the ground surface. A laser pulse can return to the LIDAR system as one or many returns. The first return includes the buildings, tree canopy and is referred to a DSM (Digital Surface Model). The last return or bare earth surface contains only the topography and is called a DEM (Digital Elevation Model).

SOFTWARE YOU NEED TO INTERACT WITH LIDAR

The Data derivatives and analysis you can perform from LIDAR mainly depends on the software and type of data you have.

Stand-alone applicationsQuick Terrain Modeler (Applied Imagery)MARS Explorer/Explorer Pro (Merrick)LAS Tools (free) http://www.cs.unc.edu/~isenburg/lastools/

ArcGIS extensionsLIDAR Analyst (Visual Learning Systems)LP360 (QCoherent)3D Analyst

SOFTWARE YOU NEED TO INTERACT WITH LIDAR

ArcGIS 10.1Supports the following datasets:• Terrain dataset 9.2• Mosaic datasets 10• LAS datasets 10.1

SOFTWARE YOU NEED TO INTERACT WITH LIDAR

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SOFTWARE YOU NEED TO INTERACT WITH LIDAR

LIDAR APPLICATIONS & USESContour MapsLand Slip Risk AssessmentBathymetricBiomass StudyMining Corridor and QuarryingFlood AnalysisHydrologySeismic HazardsPipeline SurveysHighwaysRailwaysInfrastructure DesignEnvironmental PlanningEngineering PlanningTelecommunications City ModelsElectricity and Transmission

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HYDROLOGY

DESIGN

PLANNING

LIDAR APPLICATIONS & USES

DEM DSM

CITY MODELS

RASTERS3D VIEWS

LIDAR TRAINING

ACCESING LIDAR • SC DNR http://www.dnr.sc.gov/GIS/lidarcounty.html• NOAA http://www.csc.noaa.gov/digitalcoast/data/coastallidar/index.html• USGS http://lidar.cr.usgs.gov/• OPEN TOPOGRAPHY http://opentopo.sdsc.edu/gridsphere/gridsphere?cid=datasets

• NOAA http://www.csc.noaa.gov/digitalcoast/training/intro-lidar• ESRI

CONCLUSIONIn conclusion, processing large amounts of LIDAR points can be time consuming, no matter what method or software you use. It is important to take into account considerations such as: point density of your LIDAR points, desired resolution of rasters, and extent of project.Analyzing these considerations will help you come up with a plan to process LIDAR data.