[Update: The DAV system has been updated and looks a bit different as of April 21, 2016. A newer GeoZone post explains the new system.]
DAV: Operating Manual (with Photos)
Recently, the Digital Coast data team received a request for Data Access Viewer (DAV) instructions from a Spanish-speaking, Peruvian user. She was looking for free lidar to use for educational purposes. It’s odd to have received such an inquiry since DAV was built for downloading lidar, imagery, and land cover in an intuitive way, or so it was thought. On archive, the Office for Coastal Management has documents for updating processes a decade old, but they still exist today. However, we didn’t have a user-friendly how to, so it was time to have exactly that. A slide show of screenshots was put together and sent to our friend from Peru. Then we decided the savvy and novice DAV user would get something out of an operations manual. DAV gives access to about a thousand coastal data sets, including but not limited to elevation, imagery and land cover. Users want to come in to get what they need easily (and quickly) without hassle. Our data team sees this system every day so we forget about the “usability” for someone who has never used the system before. I’m going to take a moment to give a beginner’s guide.
First task—find the site. Seems easy, right? It is fairly easy nowadays with search engines, so just search for “NOAA Data Access Viewer.” It should be the top result! (Just in case it isn’t, bookmark this—coast.noaa.gov/dataviewer). Users can also find the site via the Digital Coast’s Data Registry, albeit with a few extra clicks, along with hundreds of other data sets all in one spot with each having appropriate links for downloading (coast.noaa.gov/dataregistry).
Inside the DAV there are filters that can be set to speed up the whole process. For instance, under Data Type, a user can limit the data display to elevation or imagery or landcover; Provider will limit only those projects associated with certain organizations or institutions, such as NOAA, USGS, or USACE; and drawing an area of interest (AOI) can hone in the exact area users need. These filters can be used in tandem or separately, your choice.
Clicking Draw Area, then drawing the AOI will not only zoom in but also display all the projects in the area. Depending on Internet and computer speeds, this can take some time, so don’t fret if it doesn’t pop up right away. The service is calling a map service to find all intersecting project extents.
The pane on the left lists projects chronologically with a few highlights of the metadata and quick actions options. Overwhelmed by the number of projects? We can use the same filters from earlier or simply zoom in farther, further honing the search to exactly what is needed. If an AOI contains too many pixels or points for a particular project, a small yellow yield icon displays beside the grayed-out Add to Cart button. This means the AOI surpasses the data limit (6 GB for imagery and land cover or 500,000,000 points for lidar) so this particular data set cannot be added to the cart until the AOI is smaller.
A “power user” can download entire data sets rather quickly by using the ftp or LAZ fmt links on the right of the project information pane. Though beware, bulk downloads are only available in lossless compressed formats with default projections, units, and horizontal and vertical datums (see ftp metadata for specifics as they change depending on data type and even geography), whereas DAV orders can be customized to specific datums, coordinate systems, formats and even specific data type options, such as specific classes for lidar downloads.
Those default limits are still a lot of data! The newer lidar and imagery are dense, high-resolution products so downloading an entire project is becoming increasingly rare with a single AOI. Instead, users can draw multiple AOIs and add multiple “requests” to a single order. What we’ve learned is that even these multiple requests inside of an order have limits (personally I discovered that 30 small boxes will pretty much break all the services and again when testing the system, 10 orders broke things). In order to keep our automated system automated, requests should remain as small as the user needs. This intrinsically increases processing times and the user gets data faster. If the order is complete, then on to Checkout. This should have popped up after the first Add to Cart click.
At Checkout there are a series of four tabs the user will need to view and verify. The first notification screen basically performs a few checks before allowing users to edit choices. Then, a screen where all the magic happens. Let me edit choices allows users to edit output drop-down menus or keep it straightforward with default values.
You want Corps of Engineers JALBTCX topobathy lidar contoured ground points in UTM Zone 17 in meters with ellipsoidal heights in feet, AND in an AutoCAD dxf format? Yeah, we can do that, just give me an AOI and an email address.
Like a Staples Easy Button…no problem. There are lots of other combinations for lidar too. The third tab is where the user inputs an email address to receive an email with links to an FTP download site for the created data. And finally, a confirmation tab to secure and start the process. Within a couple minutes the user will receive a confirmation email, then within minutes or hours (depending on the AOI size), more emails will direct the customer to download locations. And, of course, a final Summary email of everything with a few more links that may be of relevance or interest.
Compared to other portals and tools for downloading geospatial data, the Data Access Viewer has taken data display, discovery, and recovery to a new level of ease. And we’re working to improve the system. With input and ideas from internal staff, partners, and users, the next release will be even easier to use and have a couple more bells and whistles to offer the user. If there are any questions pertaining to DAV, Data Registry, downloading of other data, or just a plain ol’ questions about data, contact the Digital Coast data team.