OVERVIEW

MassGIS has derived two images representing forested area in Massachusetts, for use in the Massachusetts Resource Identification Project:

1) The GAP Forest datalayer is a derivative of the Southern New England Vegetation datalayer, a GAP project component.  An image was created from the original GAP SNEVEG 1.0 data set (in ARC/INFO Grid format) by selecting the following landcover classes (alliance level):

Forested Wetland

Suburban Forest

Conifer

Mixed

Oak/Maple/Birch

Birch Dominant

Oak Dominant

Red Maple Dominant

Northern Hardwoods

View a full ist of GAP codes (.dbf, 13 kb)
View the GAP Forest Image on the Web

2) The MRLC Forest datalayer is a derivative of the National Land Cover Datalayer (NLCD) developed from Thematic Mapper satellite data acquired by the Multi-Resoultion Land Characterization (MRLC) Consortium.  The following landcover classes (with class numbers in parentheses) were selected from the original MRLC NLCD data set (in ARC/INFO Grid format):

Deciduous Forest (41) - Areas dominated by trees where 75 percent or more of the tree species shed foliage simultaneously in response to seasonal change.

Evergreen Forest (42) - Areas dominated by trees where 75 percent or more of the tree species maintain their leaves all year.  Canopy is never without green foliage.

Mixed Forest (43) - Areas dominated by trees where neither deciduous nor evergreen species represent more than 75 percent of the cover present. 

Deciduous Shrubland (51) - Areas dominated by shrubs where 75 percent or more of the shrub species shed foliage simultaneously in response to seasonal change.

Woody Wetlands (91) - Areas of forested or shrubland vegetation where the soil or substrate is periodically saturated with or covered with water as defined by Cowardin et al.

View the MRLC Forest Image on the Web

New Grids were created from their respective subsets and then converted to Tiff images in ARC/INFO.  Both images are available in Tiff and MrSID format. File names are as follows:
 

Gap Forest MRLC Forest Tiff gap_for.tif mrlc_for.tif MrSID * gap_for.sid mrlc_for.sid * - MrSID images created from Tiffs at 20:1 compression

Download these layers

There are no attributes associated with the images. Creating a map legend for the GAP and MRLC Forest images may be achieved by using the CODE item in the coverage MRLCLEG. Values of CODE correspond to the classes of forest type. MassGIS has created two ArcView legend files - gapfor.avl and mrlcfor.avl - to be used for this purpose.  The legend files and coverage (in ESRI Shapefile and Arc/Info Export File formats) are distributed with the images.

These derived images depicting select forest class information allow users to directly focus on forest-related landcover, without first having to extract the features from a larger dataset with many additional landcover classifications.  Providing the information in image format extends the data to GIS users who do not have GIS software supporting the ARC/INFO Grid format.  The GAP SNEVEG and MRLC NLCD datalayers may be obtained in Grid format with original attribute information per special request from MassGIS.

GAP Project: http://www.gap.uidaho.edu/default.htm.
Development of the MRLC Forest datalayer: http://edcwww.cr.usgs.gov/programs/lccp.

Last Updated 3/9/2005
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