Why are there so many U.S. government elevation data and information sites? Isn’t this duplication of effort? That’s a good question and one someone sent in to us recently, so I thought I’d review the ones I know about. Note that any critical comments are purely my own and don’t reflect a government opinion.
Let’s start with the following sites: National Digital Elevation Program, U.S. Interagency Elevation Inventory, NOAA Bathymetry and Digital Elevation Models Viewer, USGS National Map, USGS Earth Explorer, NOAA Digital Coast Data Access Viewer, and OpenTopography. There are probably more out there too, but this should cover the majority of the federal sites with civilian data.
The NDEP site has had two purposes. First, to let the public know there is a federal interagency group focused on elevation (primarily data collection coordination and to work through technical issues); and second, to make accessible a project tracker to show planned data acquisitions on a map, facilitating coordination. Geospatial One Stop used to harvest data from the NDEP tracker, so agencies only had to enter it once, plus the tracker had the more detailed shapes instead of the bounding box in GOS. Now that GOS is gone and data.gov is here, the tracker will likely need to be re-examined. There is no actual elevation data on the NDEP site, though adding some links to some of the other sites wouldn’t be a bad idea.
The USIEI also doesn’t host data, but it does provide data discovery so you can see what data exists in the U.S. on an interactive map and most of the data has links to where the data can be accessed. Those data access points span many different sites, including numerous state and local data repositories. The USIEI doesn’t have everything though. The topography focus has been on the larger collections of high accuracy data, typically lidar, that are in the public domain. The bathymetric data is focused on the federal data sets, mostly from NOAA, and many of the state and academic bathymetry data sets are missing. However, given the lack of an accessible inventory of the nation a few years ago, this is a very good start. The USIEI is being updated on an annual basis and may be able to add more of the missing data as resources allow.
NOAA Bathymetry and Digital Elevation Models Viewer
This NOAA bathymetry site provides discovery and download of data housed at NOAA NGDC in Boulder, Colorado. This is where you’ll find NOAA hydrographic survey data and many bathymetric data sets going back over 100 years. The USIEI entries for NOAA surveys using acoustics will generally point to this site. Also on this site are the DEMs that have been created for NOAA Tsunami modeling. NOAA is responsible for stewardship of bathymetry and this is the site that provides public access.
The National Map holds the USGS flagship National Elevation Dataset (NED). This is a raster product that seamlessly covers the nation and is updated on a regular basis as new data, such as lidar, comes in. USGS is responsible for the stewardship of topography in the same way that NOAA is responsible for bathymetry and this is their main site for the public to get that data. A notable difference is that while the NED is a best available composite of data sets, the NOAA bathymetry is kept as individual data sets.
USGS Earth Explorer
The Earth Explorer was originally designed for satellite and aerial imagery, but it now houses the lidar data that used to be in the Center for Lidar Information Coordination and Knowledge (CLICK). This is likely the largest collection of point cloud lidar data for the U.S. and I believe most government agencies send copies of their lidar data to USGS for hosting here, which is great! The downside, in my opinion, is that the site wasn’t really designed to handle lidar data. It’s fine if you just need a tile or two of LAS data, but not if you need a county worth. The USGS is aware of these problems and is working toward a new era of elevation data (see 3DEP).
I admit I’m a bit biased in favor of the Digital Coast DAV since I did a lot of the development work for the elevation parts. The Digital Coast is focused on the coastal zone, so the DAV tends to only have elevation data, almost exclusively lidar, in coastal states and territories. This leads to a fair amount of data overlap with Earth Explorer for the topographic data. The primary difference is the services available. The DAV system will allow you to select your area of interest and do some custom processing of the data. That could be as simple as changing projections and datums of the point data or as complex as deriving contours from the points. While there are limits to how much data we allow in a custom job (currently 500 million points worth), you can download complete data sets in compressed LAZ format as described in an earlier GeoZone post. Digital Coast is also where you’ll find the JALBTCX topobathy lidar point clouds.
Another site that should be mentioned is OpenTopography. Although it is not a .gov site, OpenTopography is supported by NSF and began with a focus on lidar from NSF funded Geoscience Network Project. It has expanded somewhat from purely Earth science research projects and now hosts some data sets with significant areal coverage. The services available are similar to those in the Digital Coast, allowing custom data sets to be derived from the point clouds.
Well, there are a lot of sites. It would be nice to have one stop shopping. That was the idea behind Geospatial One Stop and is the idea of data.gov. But those are still metadata driven discovery tools and never did host the data. The different sites serve different purposes and/or audiences, though I think we will be seeing some sort of consolidation to make it easier for users, particularly if 3DEP comes to fruition. I hope I’ve given you some idea of what these sites are for and made it easier for you to find the one that meets your needs.