![]() ![]() Because of their large file size the scans were registered directly to the NAD83 MA State Plane meters coordinate system instead of to NAD27 and projected. The same paper maps were scanned for the seamless statewide mosaic image, but at 500 dpi (in late 2000-early 2001). For example an image that covers part of Northfield, MA, with lower right corner coordinates of 125000m 983000m, is named q125983. 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'. The quad images are stored with the DOQ tiling scheme to facilitate storage of the images and allow for faster drawing times for local map extents. Afterwards, the grid was clipped by a DOQ template and each clipped grid was converted back into a TIFF image. The resulting grid was projected into NAD83 MA State Plane meters. In Arc's GRID module they were then clipped of map marginalia and merged with neighboring sheets. After registration, the images were converted to grids. Each scanned quad, based on the paper quad index layer, was registered to MA State Plane NAD27 in ARC/INFO with the REGISTER command. The original 4km x 4km images (produced in 1995) were scanned at 250 dots per inch (dpi). The maps were scanned with a Tangent CCS500-50TF drum scanner into 8 bit compressed TIFF images. Unfolded USGS quadrangles were used if available. The paper maps were converted to image format by scanning. ![]()
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