Database Reference
In-Depth Information
Importing LiDAR data
Light Detection And Ranging
(
LiDAR
)aredatacollectedthatmeasurethe3Dloc-
ation and other properties of objects in space. LiDAR is similar in many respects to
radarinthatituseselectromagneticwavestomeasuredistance,brightness,andoth-
erproperties.Itisdistinctfromradarinthatituseslaserand,thus,opticaltechniques,
insteadofmicrowavesorradiowaves.AnadditionaldistinctionisthatLiDARtypically
sendsoutasinglefocusedpulseatanygiventime,awaitsareturnpulse,andrecords
it.Radar,bycontrast,willsendoutmultiplepulsesbeforereceivingreturnpulsesand,
therefore, requires additional processing to determine the source of each pulse.
LiDARdatahasbecomequitecommoninconjunctionwithbothgroundandairborne
applications, aiding in ground surveys and enhancing and substantially automating
aspects of photogrammetric engineering. As such, data sources for LiDAR data
abound.
LiDAR data is typically distributed in an interchange format called
LAS
or
LASer
.
The
American Society for Photogrammetry and Remote Sensing
(
ASPRS
)estab-
lishestheLASstandard.LASisabinaryformat,soreadingittopushintoaPostGIS
database is non-trivial. Fortunately, several open-source and partially open-source
tools exist to convert and process LAS files, including LASTools and libLAS.
Getting ready
OursourcedatawillbeintheLASformat,whichwewillconvertwitheitherLASTools,
available from Martin Isenburg at
http://www.cs.unc.edu/~isenburg/
or utilities built
around libLAS at
http://www.liblas.org/
.
For Windows users, we recommend Martin
Isenburg's tools as they tend to trend toward more advanced functionality but pay
closeattentiontolicensetermsoruselibLASinstead,asthelicensingismuchmore
permissiveforlibLAS.ForLinux/UNIXandMacusers,werecommendlibLASasitis
easier to install and maintain.
LAS data can contain a lot of interesting data, not just X, Y, and Z values. It can in-
clude the intensity of the return from the object sensed and the classification of the
object(groundvs.vegetation vs.buildings).WhenweconvertaLASfiletotextand
thenplaceitinourPostGISdataset,wecanoptionallycollectanyofthisinformation.
Inpreparationforthis,wewillcreateatablewithappropriaterowstocollectsomeof
the information from our pending LAS file.
