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Overview
The Massachusetts Division of Fisheries and Wildlife (MassWildlife) has mapped bathymetry (measures of water depth) at a scale of 1:10,000 for some inland water lakes and ponds in Massachusetts. The data were gathered on boats by a GPS/depth sounder. The data samples were then extrapolated to form contour lines. The Massachusetts Department of Environmental Protection provided sounding data gathered during water quality surveys to augment MassWildlife's data for a small number of water bodies.
Bathymetry was mapped from manual methods for many water bodies in the 1950s, 1960s, and 1970s with little data from depth soundings. The new effort aims to replace the historic data with high-density bathymetry for lakes and ponds with public access and recreational angling usage.
MassGIS stores the GIS datalayer as DFWBATHY_ARC.
Production
In the field, bathymetric data were collected using a coupled GPS and depth sounder that records paired depth soundings and X/Y coordinates. The data were captured along transects at two second intervals. The density of the transects and thus the number of soundings collected within a water body varied, depending upon the size of the water body and any impediment to data collection (docks, rocks, etc). Any outliers or anomalous depths were removed manually using the R statistical package and ArcGIS.
The depth data were imported into ArcGIS as points and interpolated into 1-meter raster grids using inverse distance weighting techniques. The shoreline of the water body was heads-up digitized in ArcGIS atop ortho imagery. The grids data were smoothed using focal statistics methods and clipped to the shoreline. Depth contours were created at an appropriate interval, usually 2, 5, or 10 feet.
Attributes
The DFWBATHY_ARC attribute table has the following fields:
| Field Name | Description |
| NAME | The name of the water body |
| DEPTH | The contour depth, in feet; a 0 value denotes a shoreline or island. |
| PALIS_ID | An ID of the water body from the Ponds and Lakes Information System |
Maintenance
This data layer is maintained by MassGIS and the MassWildlife GIS program.
In December 2017 MassWildlife added data for 85 lakes and ponds. More will be mapped as part of an ongoing effort to revise bathymetry for lakes and ponds in the Commonwealth for which there is public access. The data layer will be updated as needed.