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Overview
The Digital Quadrangle Template is used as the index layer for the QUAD and QUAD2 libraries at MassGIS, which store1:25,000 U.S. Geological Survey's Digital Line Graph (DLG)-based data. This digital quadrangle template comprises 211 quadrangles. The grid differs from the USGS Topographic Map Quadrangle Template, which is based on the 1:25,000 USGS 7.5 minute topographic quadrangles and used for paper maps. For most of Massachusetts, though, the paneling schemes are identical. The quadrangle panels and numbering scheme vary along the coast, primarily for the Cape and Islands quads. For details see the Index Map
In ArcSDE the layer is named USGSGRID_POLY.
Production
The layer was created in coverage format by the ARC/INFO GENERATE command. Using the PROJECT command, the coverage was projected into Massachusetts State Plane Feet, NAD27. The coverage was then built and attributes added to the polygons to identify the digital quadrangles. One additional quad was added to the coverage for ease of processing some of the coastal data. This quadrangle (DIG-ID = 158-S), however, may not correspond to USGS DLG data.
Attributes
The polygon attribute table contains the two items to identify each quadrangle:
| QUAD_NAME | 25 | 25 | C | Quadrangle name |
| DIG_ID | 5 | 5 | C | Quadrangle identifier; may have a -W,-E or other extension |
Maintenance
This datalayer is being maintained by MassGIS.
| Date published: | April 1, 1993 |
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| Last updated: | April 1, 1993 |