Massachusetts Bay and adjacent land: Polygon boundaries for source data of a continuous bathymetry and topography terrain model of the Massachusetts coastal zone and continental shelf: (Esri polygon shapefile, Geographic, NAD 83).

PROCESS STEP 1: CREATE EMPTY POLYGON FEATURE CLASS TO STORE THE OUTLINES OF ALL THE SOURCE DATA.
Create an empty polygon feature class within a file geodatabase using the context menu in ArcCatalog (v. 10.3.1). Projection is set to UTM Zone 19 NAD 83. Add the following fields to the new feature class using the "add field" menu in the attribute table view: Source, SurvYear, PubLink, SourceType. All processing steps were completed by Brian Andrews.

PROCESS STEP 2: CREATE POLYGON BOUNDARY FILES FOR ALL LiDAR DATA.
An 8-bit integer raster was created for each source LiDAR GeoTIFF listed in "Step 2" of the MassBay_10m.tif metadata using the grid query "Value less than 1000." The resulting integer raster was converted to polygon using the Raster to Polygon tool in ArcGIS (v. 10.3.1).

PROCESS STEP 3: CREATE BOUNDARY FILES FOR SWATH AND MULITBEAM DATA.
An 8-bit integer raster was created for each source swath bathymetry grid listed in "Step 3 and 4" of the MassBay_10m.tif metadata using the grid query "Value less than 0." The resulting integer raster was converted to polygon using the Raster to Polygon tool in ArcGIS (v. 10.3.1)

PROCESS STEP 4: CREATE BOUNDARY FILES FOR ALL HISTORICAL NOS SOUNDING DATA.
Create an empty polygon feature class for each of the historical NOS surveys using the context menu in ArcCatalog (v. 10.3.1). Projection is set to UTM Zone 19, NAD 83 (2011). Edit each of the polygons and digitize a boundary that encompasses all the input soundings.

PROCESS STEP 5: CLIP AND MERGE THE SOURCE POLYGONS INTO ONE FEATURE CLASS.
This process was completed in three basic steps based on a data hierarchy using both qualitative and quantitative comparison between datasets in any areas of overlap. Starting with the LiDAR data, the individual polygons for each of the LiDAR surveys were compared for areas of overlap. In areas of overlap the newest LiDAR data with highest quality was generally used to clip (remove) overlapping older data used to create the terrain model. Qualitative criteria for determining which data to keep in areas of overlap included data density, data collection date, and data quality (are survey line artifacts visible). For example, along the south shore of Cape Cod, overlap exists between the 2007 and 2010 Army Corps of Engineers surveys. The full extent of the 2010 survey was used to clip (remove), the areas from the 2007 polygon because the 2010 data were more recent. The resulting clipped polygons were used later to extract the desired data for export as multipoint feature classes into the feature dataset used to create the terrain model. The vertical difference between overlapping raster data (LiDAR, swath, or multibeam) was used as a quantitative criteria for determining which data to retain in areas of overlap. Once these comparisons were conducted the polygons were clipped, then appended to the "MassBay_Source" feature class created in Step 1 above.
Second, the polygons for swath and multibeam created in Step 3 above were clipped and appended to the "MassBay_Source" feature class in a similar manner as the LiDAR polygons. Polygon masks of newer multibeam data were used to clip older survey data in the areas of overlap. The final polygons representing swath and multibeam data were used later to extract the desired depth data for export as multipoint feature classes to create the terrain model. Each source survey was exported as a separate multipoint, or simple point, feature class to facilitate data management.
Finally, the polygons for each of the historical NOS surveys from Step 4 above were compared in areas of overlap with newer multibeam or LiDAR data and clipped to remove older historical sounding data. During the clip process, an additional buffer of 50 to 100 meters was applied using the "Buffer Distance" in the ArcGIS Clip Tool under the Edit Menu. This 50-100 meter gap created a smoother transition during the gridding process between high resolution data (LiDAR and multibeam) and low resolution data (historical NOS soundings). These edited polygons were then used to extract the desired sounding data for export as point feature class into the Terrain Model feature data set. The final polygons for each survey were appended to the "MassBay_Source" feature class.

PROCESS STEP 6: EXPORT FEATURE CLASS TO SHAPEFILE.
Finally, exported the MassBay_Source feature class into a Esri Shapefile using the context menu in ArcCatalog (v. 10.3.1). The projection of the output shapefile was set to Geographic NAD 83 during the export process.

Added keywords section with USGS persistent identifier as theme keyword.