Below are links to the files that make up the 2020 NOAA NGS Topobathy Lidar: Guam dataset.
Vertical datum | Guam Vertical Datum of 2004 (GUVD04) using GEOID12B in meters |
Horizontal projection/datum | NAD83(MA11) / UTM zone 55N |
Informational files are listed first (such as geospatial indices, metadata, and so on), followed by the files. To download in bulk, it is suggested you use a download manager such as wget, uget, or filezilla for example. 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 will take you here).
The files are in LAZ format, a lossless compressed version of the ASPRS LAS format. The compression and decompression can be done with the free and open source 'laszip' program available at https://rapidlasso.de/laszip/ (source at https://github.com/LASzip/LASzip). This is not the same as the more general zip format. You may also want to try the uGet program using the list of URLs in file urllist_2020_ngs_topobathy_guam_m9322.txt. Several posts on the GeoZone blog provide help with downloading, including:
Example to download entire data set using wget (note: sufficiently new and trusted pre-compiled Windows versions can be hard to find):
wget -np -r -nH -L --cut-dirs=2 https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/laz/geoid12b/9322/index.html/
This will give you the directory structure starting with geoid12b. Modify the --cut-dirs=2 argument to modify
the start directory (e.g. --cut-dirs=4 will start at $missionid). Wget is a command-line program and the output will
be to the directory you run it in. More options and information can be found at https://www.gnu.org/software/wget/manual/wget.html.
The other options in the example mean:
The total size to download all the files is 335G. 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 |
See entwine.io for more information on the Entwine Point Tile format.
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