LiDAR Applications inSurveying and Engineering2013 NC GIS ConferenceRaleigh, NCFrank A. “Alex” Rankin, III PE, PLS
What is LiDAR?• Light Detection and Ranging• Analogous to RADAR, but using a different partof the electromagnetic spectrum• RADAR uses radio waves or microwaves
What is LiDAR?• LiDAR uses light at or near the visible spectrum(Visible spectrum occupies 390 nm - 700 nm)• Aerial mapping LiDAR generally uses 1064 nmYttrium-Aluminum-Garnet lasers
What is LiDAR?• LiDAR uses the laser to illuminate a target andthen analyzes the reflection• The narrow laser beam makes it possible to mapobjects with a high degree of resolution
What is LiDAR?• The basic technology has been aroundsince the 1970s, but ---• Because of size, cost and complexity hadlimited (government) application, but ---• Recent dramatic advances in laser anddetection technology, computationalspeed, and memory storage have madecommercial applications possible
What is LiDAR?• Smaller, faster, smarter LiDAR makespossible direct measurement of complexand hard to access structures
What is LiDAR• Depending on the wavelength laser used, LiDARcan develop 3D point clouds of a wide range ofobjects, such as – rocks, non-metallic objects,rain, chemical compounds, aerosols, clouds,and even single molecules
What is LiDAR• For Surveying and Civil Engineering themost important applications are aerialscanning and terrestrial scanning
What is LiDAR• Terrestrial Scanning creates 3D models ofcomplex objects: piping networks,roadways, archeological sites, buildings,bridges, etc.
What is LiDAR• One of the advantages of Terrestrial Lidaris that objects can be measured remotelymaking operations such as measuringroadways under traffic much safer.
What is LiDAR• Aerial Scanning has many uses -measuring agricultural productivity,distinguishing faint archeological remains,measuring tree canopy heights,determining forest biomass values,advancing the science of geomorphology,measuring volcano uplift and glacierdecline, measuring snow pack, andproviding data for topographic maps - toname a few…
Topographic Mapping• In the past decade,because of theadvantages of LiDAR,it has largelydisplacedPhotogrammetry asthe process fordevelopment of largescale topographicmaps
Topographic Mapping(LiDAR Advantages)• LiDAR sensors canbe operated in anyweather – (not so withcameras- the cloudsget in the way)• LiDAR sensors arenot affected by lowsun angles - whichwould prevent usefulphotos
Topographic Mapping(LiDAR Advantages)• IN FACT – LiDAR canactually operate atnight!• More hours of usefulflying per day meansLiDAR offers greaterefficiency, fasterresults, and can covermore ground thanphotogrammetry
Topographic Mapping(LiDAR Advantages)• Rural and remoteareas are easier andquicker to survey withLiDAR because eachpoint has geo-referenced locationand elevation – noorthorectification ofimage – no network ofphoto panels required
Topographic Mapping(LiDAR Advantages)• Photogrammetryneeds to be able tosee the ground tocreate contours• LiDAR returns comefrom every objectilluminated – thelowest being theground – whereverthe sunlight hitsLiDAR will return XYZ
Topographic Mapping(LiDAR Advantages)• LiDAR creates a 3D model directly from the returns• Photogrammetry requires the incremental comparison ofa pair of stereoscopic photographs – indirect and muchmore labor intensive
Topographic Mapping(LiDAR Advantages)• Photogrammetry requires contrast to see groundsurfaces – desert, wetlands, beaches, coastsare difficult or impossible• LiDAR results come directly from the returnedsignal – contrast not required
Public LiDAR Resources• Public sources of existing LiDAR arevaluable resources for engineering andsurveying firms – some addresses are:• http://www.ncfloodmaps.com/• https://connect.ncdot.gov/resources/gis/Pages/Cont-Elev_v2.aspx• http://www.nconemap.com/
Public LiDAR Resources• These public sources are excellent forlarge scale planning processes…However……!
Public LiDAR Resources• North CarolinaBoard ofExaminers forEngineers andSurveyors,says….….in its Spring 2012newsletter…
Public LiDAR Resources“As to the useof…floodplainmapping LiDARelevation data shouldnot be used for finaldesign…” or it“…could lead todisciplinaryaction…”
Public LiDAR Resources• But properly used these public sources providethe base information for all types of planningprocesses, such as – developing project specifichydrology models for large areas…
Public LiDAR Resources• …or for developingland use plans forlarge residential,commercial,industrial, or mixeduse areas….
Public LiDAR Resources• …..or for view shedsfor parks, trails, andother large outdoorrecreational areas….
Public LiDAR Resources• ….evaluating the relationship to environmentalsites….
Public LiDAR Resources• …planning for greenways and other recreationalamenities….
Public LiDAR Resources• …planning industrial sites….
Public LiDAR Resources• …industrial site selection by “site selectionconsultants” (hired guns)….
Public LiDAR Resources• …and beyond initial planning the public sourcescan be used for large scale schematic gradingexercises…
LiDAR in Civil/Surveying Firm• Terrestrial LiDAR (Scanning) can rapidly mapcomplex sites in much more detail than ispossible with conventional means – this makes abetter base sheet for design….
LiDAR in Civil/Surveying Firm• …and even if not complex, it covers areas thatare large (but too small to fly) quickly….
LiDAR in Civil/Surveying Firm• Imagine a building – filled with piping….
LiDAR in Civil/Surveying Firm• …imagine crawling around that piping trying tolocate it by direct measurement…
LiDAR in Civil/Surveying Firm• …andthe cost(andtime)savingsbecomeobvious.
LiDAR in Civil/Surveying Firm• For largerareas, sitespecific aerialLiDAR providesbase sheets forall types ofproject specificcivil engineeringdesign…suchas…
LiDAR in Civil/Surveying Firm• …MasterPlanning…