SIM3402_readme.txt

These files constitute the digital database, in GIS format, for USGS 
SIM 3402, "Surficial materials of Massachusetts--A 1:24,000-scale geologic 
map database" by Janet R. Stone, Byron D. Stone, Mary L. DiGiacomo-Cohen, 
and Stephen B. Mabee.

The database represents the information displayed on both the 1:250,000-scale 
index map PDF and on the 1:24,000-scale quadrangle map PDFs. It is recommended 
that users of the geodatabase read the complete explanatory pamphlet and metadata. 

Note that the geodatabase, shapefiles, and base map layers in this report are 
all in Massachusetts State Plane Coordinates, NAD 83 (meters).

The geodatabase uses a slightly modified version of the National Geologic Map 
Database GeMS format (formerly NCGMP09); documentation of the standard can be 
found at https://ngmdb.usgs.gov/Info/standards/GeMS/. Specifically the GeMS 
format requires ContactsAndFaults, but we have chosen to omit this feature. Our 
original design of the database consists entirely of overlapping (stacked) 
polygons in contrast to the Gems MapUnitPolys, which must not overlap and must 
maintain topology with the ContactsAndFaults. 

However, because of the interest in and (or) demand for a "surface only" map layer, 
we have created a slightly generalized version of the geologic features for our 
MapUnitPolys (geologic polys have been clipped through from top to bottom (youngest 
to oldest) without overlaps; some small sliver polygons have been eliminated). 
The MapUnitPolys feature must be used with the OverlayPolys (representing shallow 
bedrock), which are true overlay polys (shown as a lined pattern). The original data 
consisting of stacked units (including shallow bedrock) is stored entirely in the 
MapUnitOverlayPolys feature. Depending on your application you may find it easier 
to use the simplified MapUnitPolys and OverlayPolys option. The index map and the 
quadrangle PDFs were created using the full layered data in the MapUnitOverlayPolys 
feature. Be sure to display the polygons in their correct order from youngest to 
oldest using the associated .lyr files. 

The geodatabase is presented in three formats:

1) sim3402_GeMS.zip: Contains SIM3402.gdb, an ESRI ArcGIS v. 10.5 
file geodatabase laid out in accordance with the GeMS (formerly known 
as NCGMP09) database schema. A description of this schema is available at 
https://ngmdb.usgs.gov/Info/standards/GeMS/. FGDC-style metadata for 
each element of the geodatabase (table, feature dataset, feature 
class) are stored within the geodatabase. The zip file also includes 
report-level metadata, an ESRI .mxd file that describes a map image 
similar to that in .pdf, .lyr files, and a RESOURCES 
folder that contains an ESRI .style file. 

2) sim3402_open.zip: A complete, automatic translation of 
SIM3402.gdb into shapefiles, dbf files, and pipe-delimited text 
files for fields longer than 255 characters. Logfile.txt documents how 
fields were renamed to fit within the 10-character fieldname-length 
limitation of the shapefile format. Also contains report-level 
metadata and the .lyr files. This complete version of the database 
contains all the content of the native geodatabase transcribed into 
well-documented, stable file formats. 

3) sim3402_simple.zip: Automatic translation of MOST of the contents 
of SIM3402.gdb into simple flat shapefiles. This is an easy-to-use, though 
incomplete, version of the database. The zip file also contains 
report-level metadata and the .lyr files. 

The BaseMaps folder contains georeferenced tiff images for each quadrangle; 
these are the old-series (1944-1977 editions) topographic quadrangles 
(1:24,000 scale), most of which have the same contour base (10-ft contour interval) 
as the original geologic mapping. Each quadrangle has the following file component 
extensions: .tif, .tfw, and .tif.lyr. Paper quadrangle maps were scanned and 
georeferenced by the Office of the Massachusetts State Geologist for this project. 
These images carry no warranty or metadata; they may not be useful for any other 
project or purpose. Each of these images has an associated layer file which 
colormaps the image so that the white background becomes transparent; they should 
be used on top of the geologic data layers. SIM3402.mxd uses relative path names, so 
as long as the directory structure for the images remains the same (\SIM3402\BaseMaps\), 
they should load correctly. 

These files, as well as PDF files for publication-quality images of the map sheets
and pamphlet, are available at https://doi.org/10.3133/sim3402.


Mary DiGiacomo-Cohen
U.S. Geological Survey
101 Pitkin St.
East Hartford, CT 06108
mdicohen@usgs.gov