1:24,000-Scale, 10-foot Contour Topographic Maps for Massachusetts
About these Products
This archive contains georeferenced tiff images of nearly all the older, 10-foot contour, 7.5-minute topographic quadrangle maps for Massachusetts. The dates range 1944 to 1977. These are the maps that were originally used to map the surficial geology across the state at 1:24,000 scale and are considered more reliable than the newer 3 m contour, 1:25,000-scale metric maps. The archive contains 188 files. The only quadrangle missing is the Hampton, NH quadrangle, which contains a very small sliver of Massachusetts in the southwest corner of the quadrangle. The complete list of the maps including the date of the map and contour interval is provided in an accompanying file named DateofMapsinArchive.xls. The files have been zipped and identified by the quadrangle name. In each zip file are four or so files, a tiff image, an xml file for georeferencing, .rrd and .aux files. Some contain .lyr files.
The files can be unzipped and imported into ArcGIS 9.x and ArcView 3.2. In ArcMap, convert the white layers to transparent and the map will lay over any other vector data as a transparent base map.
Scanning and Georeferencing
Unfolded copies of the paper maps were scanned at 400 dpi as a 24-bit color map and saved as a jpeg. Marginalia was cropped to the map border in Adobe Photoshop. The raster image was processed using the Auto Level, Gaussian blur (radius = 0.5 to 2 pixels), and unsharpen mask tools in Photoshop then converted to a 256 color index RGB image. Unwanted colors such as pink urban areas and green forests were removed using the Color Range tool in repeated trials. The cleaned image was saved as a tiff.
The cropped and cleaned tiff image was loaded into ArcGIS 9.1 and georeferenced to the interior and exterior latitude and longitude tick marks on the map. This included approximately 6 to 9 reference points per map. A second order transformation was performed. An RMS of <6 meters was specified for georeferencing. Images were rectified. All maps are georeferenced to Mass State Plane coordinates, North American Datum of 1983. Details regarding the scanning and georeferencing process are available upon request.
webpage last updated 2/8/2007