|US National Map View of Maumee, Ohio|
|The same view of Maumee, Ohio with the aerial image|
background turned on
The US National Map is not a map per se. You can't ring up the USGS and say "Send me a copy of the National Map." It doesn't exist as a single product. The US National Map is a collection of digital geographic and geospatial data that, when brought together, forms the foundational map of the United States. Here's how the USGS describes it:
"As one of the cornerstones of the U.S. Geological Survey's (USGS) National Geospatial Program, The National Map is a collaborative effort among the USGS and other Federal, State, and local partners to improve and deliver topographic information for the Nation. It has many uses ranging from recreation to scientific analysis to emergency response. The National Map is easily accessible for display on the Web, as products and services, and as downloadable data. The geographic information available from The National Mapincludes orthoimagery (aerial photographs), elevation, geographic names, hydrography, boundaries, transportation, structures, and land cover. Other types of geographic information can be added within the viewer or brought in with The National Map data into a Geographic Information System to create specific types of maps or map views. The National Map is a significant contribution to the National Spatial Data Infrastructure (NSDI) and currently is being transformed to better serve the geospatial community by providing high quality, integrated geospatial data and improved products and services including new generation digital topographic maps."
OK, like I said, it's a collection of digital geographic and geospatial data that forms the foundational map of the US. Geeze, I think government bureaucrats get paid by the word.
Here is the USGS's introduction to the National Map program and the National Map Viewer:
The National Map Viewer is the USGS's on-line portal to all the data that makes up the National Map.
The Viewer is pretty good (if you are at all interested, it is built on ESRI's ArcGIS Server technology) and offers some neat functionality. It will provide location information in a number of formats, including US National Grid coordinates, it has a pretty robust reverse geocoding feature (click on a building on the map and the map returns the street address for that location) and it will provide spot elevations from the national elevation dataset. You can do area and distance measurements, add text and simple graphics and even add data from external sources like a GoogleEarth KML file or a web mapping service. You can also bring up indexes for the USGS's standard map products like the US Topo series of maps and link to them for download as GeoPDF files. For advanced users the Viewer offers some pretty good search and query builder functionality, so you can find specific data that is embedded in the data layers.
There are some shortcomings, however. The print function is essentially useless and is perhaps THE major drawback of this Viewer. About all it does is grab a screen shot of your viewer and dumps it to a PDF file. The USGS needs to wake up and realize that people still want quality paper maps and with today's technology it should be easy to print a fully detailed paper map with things like a grid, scale indicator, geographic extents, legend, etc.
The Viewer also exhibits a common issue found in web-based maps - map content naming conventions can be pretty obtuse and downright confusing. While the Viewer does pretty good with the base data layer naming conventions, when you start using advanced features like the Query Builder you start to interact directly with the database field names. For example, if I'm building a query to identify all the wetlands in my county I'm presented with a list of 'Columns' (which are the database field names). Those column names are confusing and don't mean anything to most humans. We get to pick from selections named 'ATTRIBUTE' or 'OBJECTID' or 'SHAPE_Area'. There is an easy solution to this - the GIS professional building this map can establish what are called 'field alias' names - a human-friendly nickname for each of the information fields. ATTRIBUTE can be displayed as 'Wetland Attribute', OBJECTID can be displayed as 'Wetland ID' and SHAPE_Area can be displayed as 'Wetland Area'. This naming convention issue usually reflects the fact that GIS professionals with little cartography experience compiled the data for use in the Viewer. (If I seem to be nit-picking here it is because I build maps for a living using this same technology. I know these are issues that are easy to fix and should have been taken care of before the Viewer was opened up to the public.)
These shortcomings aside, the National Map Viewer is pretty darned good. I'd say the USGS gets a good solid 'B' for this effort. If they'd improve the damned printing issue I'd give them an 'A'.