3-meter contours created from Digital Terrain Model (DTM) data points collected during the production of 1:5,000 Black and White Digital Orthophoto images
Process_Date: before August 2001
The source elevation tile data was provided on the MassGIS website www.state.ma.us/mgis/massgis.htm in ESRI-format shapefile format and imported into IDRISI software using the ShapeIdr command. The resulting vector elevation files were converted to raster format using successive Lineras macro commands. This has the effect of mosaicing the tiles as well. The raster image was filtered once using a low-pass (mean) filter, then masked to the Ipswich study area parameters (extent).
Information relevant to the GIS data encoding
DEMHorizontal Coordinate System Name:NAD 1983 StatePlane Massachusetts Mainland FIPS 2001
Datum: D North American 1983
Reference Ellipsoid: Name: GRS 1980 Semi Axis: 6378137.0
Meridian: Greenwich
Projection Name : Lambert Conformal Conic
Number of bands : 1
Raster Origin : Lower Left
Rows : 1152
Columns : 1692
Cell Geometry :pixel