April 1, 2009 By Michael Smith
Used with permission from the Maine Office of Information Technology
In the last ten years, there has been great interest in creating highly-accurate ortho-rectified aerial photos for use in geographic information systems (GIS) in Maine, not only at the federal and state levels, but also at the municipal level. Many towns have developed such data on their own, but lack both the financial and technological resources to share these data, nor are they able to take advantage of the large amounts of data collected by state and federal agencies. As a result, several terabytes of digital aerial photos exist in the state, but the means of sharing them does not. Considering the millions of dollars spent in developing such data, it makes sense to invest a small amount more to publish the data and help it reach its true potential.
The Maine Office of GIS (MEGIS), in cooperation with the Maine Library of Geographic Information (GeoLibrary), has developed an open web mapping service (WMS) platform specifically to meet this need. MEGIS has developed a "production pipeline" comprised of scripts and open-source software that greatly decreases the time it takes to convert imagery to a WMS. The platform provides the service using OpenGIS Consortium (OGC) standards, and relies almost exclusively on open-source software such as the Geospatial Data Abstraction Library (GDAL), Python, and MapServer. The process consists of two parts - preparation of the data to create the WMS, and then a web serving platform to host it.
The purpose of this project is to partner with any organization holding publicly-available digital aerial ortho-photos for Maine in order to allow these data to be made available to any user via WMS. Such a service can easily be consumed in most GIS software including Google Earth, and can also be easily integrated into any web-mapping application. Maine's approach to this solution has spanned all levels of government in Maine, including hosting data from the federal government U.S. Geological Survey (USGS) and U.S. Department of Agriculture (USDA), state government (MEGIS and Maine Department of Marine Resources), and local government (Southern Maine Regional Planning Commission, the Greater Portland Council of Governments, and the towns of Augusta, Manchester, York, Kittery, and Hampden). This service is still early in its development and we foresee doubling the data holdings in the next six months. Collaboration was key to this service's development, MEGIS collaborated with USGS, USDA, the University of Southern Maine, and Maine GIS stakeholders via the Maine GeoLibrary. The GeoLibrary Board provided the funds to purchase the server hardware, while MEGIS provides the expertise to convert raw imagery into WMS. The other partner organizations provide their raw data in return for having free access to it via WMS.
While WMS and providing image services have been around for a few years, this project is unique in that it is the first attempt, as far as we are able to ascertain, to provide a free and openly-available platform for sharing aerial ortho-photos. Indeed, even big federal agencies such as USGS and USDA do not have platforms available to provide all of their Maine imagery via web services. The benefits of these services will be tremendous. State agencies and federal agencies will be able to tap into any imagery product available in Maine, and small municipalities will be able to provide their data outside their town offices at no expense. This solution also provides several opportunities to protect and conserve natural resources. For example, the