From briefly exploring the four different digital map download interfaces the USGS offers, I have pretty much ruled out DigitalEarth and the National Atlas. The former has a user interface so cumbersome to use for the casual browser that it’s useless, and the latter simply doesn’t have the data I’m looking for. So that leaves The National Map and the SDDS.

The National Map has a home page that is more visually appealing, has a clearer description of what its purpose is, and even sports a nifty logo.

Using the map at first seems to be simple. You’re presented with a relief map of the U.S. and can zoom and pan in it, with the default layers including highways, surface streets, and a grayscale shaded relief. Unfortunately, the layer control is in a frame that can’t be resized (frames are evil!), which makes navigating the layers a little difficult. Turning on road labels and a few hydrology layers results in a better understanding of the map, and a fairly reasonable presentation. Unfortunately, there is no way to capture a vector version of the current map view, as SVG or DXF, for example.

I found it easy to get the DRG quad images to appear, but there is no control over the order in which the layers are drawn, so it’s impossible to specify that the shaded relief be drawn on top of the photos, or blended with them. And this time, I found two different, but nearly identical high-res color images, clearly made from the same original. One (San Francisco-Oakland 2004) was sharper, but the other (Urban Areas) had richer colors. Selecting both the NED elevation data and the color photo for download proved impossible, and selecting each individually still required downloading two files separately—the metadata and the actual image. The link to the metadata failed, and since the download is always of the current display and the image was wider than I wanted, the raster image download was delivered in two pieces, split right in the middle of my desired area. Moving the split required me to “center” my desired image on the right side of the rectangular window. I can’t get rid of the split because each half of the image is 83MB, and the download limit is 100MB.

I selected one of the elevation files for downloading, but doing so opened the ZIP archive directly in WinZIP instead of asking me what directory I’d like to save it in.

Now that I understand how the game works, I’ve figured out how to get the map window to be the size I want (answer: resize the browser window, pan the image, repeat until satisfied), and have re-specified all the options. To download the raster image, and the elevation data in both TIFF and ArcGrid formats only took me 3 more modifications of the data request. So I’ve now got the 75MB TIFF image, and two flavors of the NED and SRTM elevation data.

Time for lunch.