Below are links to the files that make up the 2018 NOAA NGS Topobathy Lidar: Chesapeake Bay, VA (Fisherman Island National Wildlife Refuge to Pitts Neck) dataset.
| Vertical datum | North American Vertical Datum of 1988 (NAVD88) using GEOID18 in meters |
| Horizontal projection/datum | NAD83(2011) / UTM zone 18N |
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_va2018_ngs_ches_bay_m9074.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/geoid18/9074/index.html/
This will give you the directory structure starting with geoid18. 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 265G. There are 1527 LAZ files and the summary class table is:
| Class Number | Class Name | Points |
|---|---|---|
| 1 | Unclassified | 43087403371 |
| 2 | Ground | 4279509677 |
| 7 | Low Point (noise) | 371353665 |
| 40 | Bathymetric point | 1149649972 |
| 43 | Submerged Object | 8866707 |
| 45 | Water column | 6131179689 |
See entwine.io for more information on the Entwine Point Tile format.
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