2020 NOAA NGS Topobathy Lidar: Guam Point Cloud files with Orthometric Vertical Datum Guam Vertical Datum of 2004 (GUVD04) using GEOID12B

Below are links to the files that make up the 2020 NOAA NGS Topobathy Lidar: Guam dataset in an orthometric vertical datum Guam Vertical Datum of 2004 (GUVD04) using GEOID12B. This HTML file is here to emulate the access you would have gotten through an ftp site. The files containing geospatial indices, metadata, etc., are listed first, followed by the files. To download in bulk, it is suggested you use a program such as wget (example below). The geospatial index file in shapefile format also has a URL attribute that some GIS programs can use to download files. You can also subset the data, make derived products, and change projection, datum, etc., using the Digital Coast Data Access Viewer (add to cart, the link to bulk download or LAZ fmt will take you here).

The data are all in geographic coordinates using the North American Datum of 1983 (NAD83). The version of the NAD83 datum may vary slightly, but all are one of the updated realizations such as the High Accuracy Reference Network (HARN), Continuously Operating Reference System of 1996 (CORS96), or National Spatial Reference System of 2007 (NSRS2007), and not the original NAD83(86). This may not be evident in the metadata. Vertical units are meters and all have been converted from NAD83 ellipsoid heights to orthometric Guam Vertical Datum of 2004 (GUVD04) heights using GEOID12B.

The files are in LAZ format, a lossless compressed version of the ASPRS LAS format. The compression and decompression is done with the free and open source 'laszip' program available at https://laszip.org. This is not the same as the more general zip format. Many geospatial programs will read LAZ files natively and decompression is often not necessary. There is a list of software with native support on the laszip site. This data is LAS 1.4 format compressed using laszip in native mode. You'll need laszip version 170330 or higher (or tools compiled with at least that version of laszip) to read it.

There are many download managers you can use to get all the data. An example is the uGet program using the list of URLs in file urllist9322.txt. Several posts on the GeoZone blog provide help with downloading, including:

• Using uGet to download bulk lidar
• Downloading a subset of files based on a polygon
• Downloading on Windows without additional programs

The total size to download all the files is 281G. There are 3965 LAZ files and the summary class table is:

Class Number	Class Name	Points
1	Unclassified	27690872693
2	Ground	8263839387
7	Low Point (noise)	942716593
17	Bridge Deck	960148
40	Bathymetric point	1509438583
41	Water surface	4309864587
42	Derived water surface	5191768870
43	Submerged Object	69534
45	Water column	5040637175

Georeferencing Note

You may find the georeferencing on the files refers to generic NAD83 (EPSG code 4269). All files, with the exception of the few in WGS84, are in a more recent realization of NAD83 such as NAD83(CORS96), NAD83(HARN), NAD83(NSRS2007), or NAD83(2011).

Cloud Access

Meta Info

Tile Index: tileindex.zip (Shapefile)
                2020_ngs_topobathy_guam_index.gpkg (GeoPackage)
Metadata: 2020_ngs_topobathy_guam_metadata.xml
Metadata: 2020_ngs_topobathy_guam_metadata.html
XYZ range table: 2020_ngs_topobathy_guam_minmax.csv
README: 0README.txt (contains similar information to above)
URL List: urllist9322.txt is a list of all the URLs for batch downloading.

Supplemental Info

Point Clouds