Below are links to the files that make up the 2018 NOAA NGS Topobathy Lidar: Potomac River, Chesapeake Bay dataset in an orthometric vertical datum North American Vertical Datum of 1988 (NAVD88) using GEOID18. 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 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.
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 urllist8727.txt. Several posts on the GeoZone blog provide help with downloading, including:
The total size to download all the files is 242G. There are 5968 LAZ files and the summary class table is:
|Class Number||Class Name||Points|
|7||Low Point (noise)||66868721|
|30||Submerged Aquatic Vegetation||225294|
|31||Temporal bathy bottom||30551168|
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).
Tile Index: tileindex.zip (Shapefile)
XYZ range table: 2018_ngs_topobathy_potomac_river_chesapeake_minmax.csv
README: 0README.txt (contains similar information to above)
URL List: urllist8727.txt is a list of all the URLs for batch downloading.
This page is owned by the NOAA Office for Coastal Management and was created by an automated script on Mon Dec 20 18:17:11 EST 2021