Lizard watchers will have noticed the recent LizardTech announcement regarding the Express Server sale to North Carolina. I spent an afternoon pointing Google Earth over there and reflected about the need for better public access for public GIS aerial imagery.

Like most people (certainly most people who read LizardTech’s blog) I’m really excited by the advent of feature-rich GIS clients like Google Earth and very extensive base map that they make available for free, non-commercial use. That said, there are lots of different kinds of imagery you might want to view and Google can’t provide them all. (For an interesting introduction to some of what’s behind the Google Earth base map imagery, see this Google Earth Blog posting.

Despite the availability of free or nearly free commercial data from Google, there are myriad public programs that acquire new imagery each year.

• USDA’s Aerial Photography Field Office runs several image collection programs the best known of which is probably the National Agricultural Image Progam (NAIP) which provides farm-related orthophotos
• USGS’s National Aerial Photography Program (NAPP) supports various federal agencies
• The National Geodetic Survey’s Aeronautical Survey Program supports aerial photography of Airports

That’s a by-no-means exhaustive list of federal collections programs. There are similar programs that work at the State and Local level. In general, there’s a very good reason for this: no single base map, even one as well-funded and maintained as Google’s, can hope to meet everyone’s needs.

Happily, most of that publicly-acquired data is publicly available for little or no cost to US taxpayers. The rub is the means by which it’s made accessible.

In many cases you can view maps via a web application like this NAIP 2006 Viewer and this MDOQ Viewer hosted by USDA’s Geospatial Data Warehouse. That’s great for basic access and a pan-and-zoom style of data discovery but limits the user to exactly what web application has built for you. For most non-trivial work, it’s not what you need (for example comparing / aggregating diverse datasets).

More frequently, you download the data or have it mailed to you on a DVD. Like this. That’s OK if you’re not in a rush and you have industrial strength GIS tools and the necessary technical sophistication to use them. Even then, you’re stuck with this same problem for every public dataset you need to access. Consider briefly that each of those datasets are frequently bigger than 1 gigabyte in size.

What we need are better tools and better integration. Increasingly, Google Earth is being picked as an easy, relatively inexpensive ($400/year for commercial use, free for personal use) tool and OGC standards like WMS are serving the integration need.

All of that brings me back to the the North Caroline site. Randolph County is a growing community. If you want to see the latest growth (here from 2007), you’ll need to ask the locals, it is not in the Google Earth base map, which shows this:

Here’s the same area, again inside of Google Earth, using the WMS feed from NC OneMap.

Try it yourself: Click this KML file to open it in Google Earth (Note: In Firefox, you’ll be asked first whether you want to open or save the file).

Directions magazine explored the question of the commercial data Google publishes as a public trust. My view is that, by making their real public data accessible via a common WMS interface, North Carolina has made it, well, really public.