Merging Multiple Digital Elevation Models to Create Seamless Terrain Applied to Maine and the Atlantic Maritimes

Michael Hermann
Cartographic Designer, University of Maine Canadian-American Center, 154 College Ave, Orono, Maine, 04473

Matthew Cote, University of Maine

James L. Sloan II
Gould Center for Geography Education and Outreach
Environment Institute, The Pennsylvania State University


USGS Digital Elevation Models (DEM) are the primary resource for terrain based cartography in the United States. However, for US states that share an international border this common resource fails to allow cartographers to show the geographic area beyond the US political boundary. To resolve this concern for cartographies of the state of Maine, we have merged multiple DEM resources to create a continuous coverage. These resources include USGS 1:24,000 DEMs, 1:250,000 DEMs, GTOPO30 data and digital bathymetry for the Gulf of Maine. The workflow includes using ArcINFO to reproject and export the data in a common projection; MACDem to import, colorize and export; Photoshop to merge, layer and blend; Freehand to create a matching vector coverage; and if desired; Bryce to explore 3D representation. The workflow uses only public domain data available on the internet. After the ArcINFO procedure, the workflow uses only desktop publishing software and shareware, readily available to most graphic designers and publishers. Applied to Maine, this allows the state to be illustrated in its true geographic relationship with the Bay of Fundy, St. Lawrence Seaway and the Canadian Maritimes, a cartographic goal rarely achieved in part due to the politics of US and Canadian Governments cartographic data resources.