Putting aside for a moment our controversy with ESRI over their “uncool” move to create yet another proprietary format whose only benefit is vendor lock-in (read this, this, or this for more on their “LAZ clone“), they do have some neat Web technology: The Sonoma County Vegetation Mapping and LiDAR Program is using their ArcGIS online Web maps to implement an interactive download portal for open LiDAR and derived products such as contours, building footprints, and elevation rasters.
The five year SonomaVegMap program – a joint program of Sonoma County Open Space and the Sonoma County Water Agency – aims to survey Sonoma County’s topography, physical and biotic features, and diverse plant communities and habitats. The program has already produced several products including county-wide LiDAR data which is now freely available for download as LASzip compressed LAZ files that are linked in increments of watersheds via an ArcGIS online Web map as shown below.
download portal of SonomaVegMap project using ArcGIS online
Clicking the download icon opens another window (as shown below) where the user can select either the raw LiDAR or the various derivatives (or all) and start downloading.
selecting ZIP file with LASzip-compressed LiDAR in LAZ format for download
After about an hour of downloading and a few more minutes of unzipping the 1.4 GB ‘Bodega Head LAZ Files.zip’ file we finally get to see its contents: 103 LAZ files totalling 1.4 GB that decompress to 296,897,792 LiDAR points.
A small personal plea: “Please do not put spaces in file names of folder names but use underscores instead!“. Spaces have traditionally been used to separate commands and having them in file or directory names can break batch processing or python scripting. Using the GUI of lasview we load the 103 files and see how this watershed is tiled:
The information bar on the right tells us that the LasMonkey software of Watershed Science Inc. has processed points of type 3 (i.e. with GPS time stamp and RGB color) into California State Plane II coordinates and stored them with a resolution of “centi survey feet” (i.e. scale x y z are all 0.01). We pick a horizontal strip and view the points with different visualization options.
(1) RGB (2) intensity (3) classification (4) elevation (5) flightline (6) user data (7) hillshaded TIN of ground points
Everything looks correct although we are not quite sure which values are stored in the ‘user data’ field of each point. Apparently these values more intense for water returns and maybe someone from Watershed Science Inc. will be able to enlighten us. Below a single tile as well as a close-up of one particular area of this tile followed by a lasinfo report. All 103 tiles pass the lasvalidate test with flying colors, nice job guys!
a closer look at tile ‘SOCO_0024_121.laz’ of the Bodega Head watershed
close-up with ground and building points triangulated
lasinfo report for tile ‘SOCO_0024_121.laz’
Let me close this article with a 1 minute and 30 second video that summarizes the SonomaVegMap project.
