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USGS QUADRANGLE IMAGES DATALAYER
Click here to download a MA map sheet index map in E00 or Shapefile format. OVERVIEW The USGS 7.5 minute series topographic quadrangles were scanned to create a digital database that can provide images of the paper maps. These images can be used as a backdrop for plotting vector data, and for interpretation and analysis. The images are indexed by the Digital Orthophoto Quad (DOQ) Index, producing 1537 images for the 189 paper quads. The image name is an Index sheet-id composed of the first three digits of the x and y NAD83 state plane coordinates of the image's lower right corner, prefixed by the letter 'q'. For example, an image that covers part of Northfield, MA, with lower right corner coordinates of 125000m 983000m, is named q125983. PRODUCTION The paper maps were converted to image format by scanning. Unfolded USGS quadrangles were used if available. The maps were scanned with a Tangent CCS500-50TF drum scanner at 250 dots per inch (dpi) into 8-bit compressed tiff images. Each scanned quad was registered to MA State Plane NAD27 in ARC with REGISTER. After registration, the images were converted to grids in GRID where they were then clipped of map marginalia and merged with neighboring sheets. The resulting grid was projected into NAD83 MA State Plane meters. Afterwards, the grid was clipped by a DOQ template and each clipped grid was converted back to a tiff image. These images, however, were unable to be displayed in some pc-based software (such as Microsoft PowerPoint). To correct this problem, each compressed tiff image was uncompressed in ARC and converted to a compressed tiff image in PaintShop Pro. All images may now be displayed using any software. Each zip includes image files (.tif) and associated world files (.tfw) for geo-referencing images to Massachusetts State Plane NAD83 projection. Each image covers 4000 x 4000 meters. |
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