The 2015 Dublin LiDAR point cloud and 2 older laser scanning datasets of Dublin have been ingested onto NYU Dumbo cluster. The data are accessible to anyone having access to the cluster. This post contains the code snippets you can use to extract point cloud subsets from the LiDAR database. This database is being developed as part of the Ariadne3D project. The related publication explaining the database design is available for download at the link below.
You need an NYU HPC account. See this instruction if you want to sign up for an account.
You need to be on the
login-1-1 node to work with Dumbo’s HBase. You can
ssh login-1-1 if you are assigned to
login-2-1 at the first login.
Upload the jar file listed below (i.e.
lidardb-0.0-jar-with-dependencies.jar) to a directory on Dumbo that you have access to (e.g. your home directory).
pcextract- extract a point cloud subset
Purpose: Clip a portion of the point cloud dataset using a 3D, recti-linear querying box.
java -jar [path_to_jar_file] pcextract -t [table_name] -output [path_to_output_file] -clipping_box [xmin ymin zmin xmax ymax zmax]
java -jar $HOME/lidardb-0.0-jar-with-dependencies.jar pcextract -t dublin15 -output $HOME/out.las -c 316000 234000 0 316010 234010 50
The above command extracts the points that have x bounded by
[316000, 316010], and y bounded by
[234000, 234010], and z bounded by
[0 50] from table
dublin15. The extracted points are saved into a file at
$HOME/out.las. The exported data are in the LAS format. You can use this 3D viewer to locate the data regions you need and their coordinates. The point picking tool on the control pannel on the left side of the viewer will let you read the coordinates.
Currently, Dumbo’s HBase is loaded with 3 LiDAR scans of Dublin. The table name
dublin15 in the command can be replaced by
dublin07 if the older LiDAR scans of Dublin (acquired in 2014 and 2007) are needed.
If you know the lat/lon of the region you want to extract, you can use the syntax below with the
java -jar $HOME/lidardb-0.0-jar-with-dependencies.jar pcextract -t dublin15 -output $HOME/out.las -c -6.258411705493927,53.340577164289094,-100,-6.257177889347076,53.34122894218849,500 -wgs84
The 6 parameters passing through tag
-c are: lat_min, lon_min, z_min (meters above sea level), lat_max, lon_max, z_max.
In addition to the above mandatory parameters,
pcextract takes the following parameters:
||data storage model (see details in the paper)||4|
||number of Hilbert ranges||100|
||connection details if the database is not on the localhost or at the default port|
||convert to WGS84 from a non-default SRID (EPSG:29903)||29903|
||toggle between the approximate and the accurate mode||(empty)|
||log more information for debug purpose||(empty)|
Contact me if you have questions or find bugs.