Downloads
An index is displayed in MassMapper. Choose your tiles to expose the Contour URL links. The Online map view is displayed in MassMapper at a large scale, and you can add other layers too.
Overview
Contour lines at 1 foot intervals, derived from a bare earth digital elevation model (DEM), can be displayed to aid in the interpretation of elevation data. For original vendor metadata and reports containing specific details on the source data, see the Technical Data Report
Production
MassGIS derived these contours from the USGS 2021 Central Eastern MA Lidar Project data.
The Hydro-enforced digital elevation model (DEM) and water's edge breaklines were processed in ArcGIS Pro 3.0.3 using the Contours with Barriers3DAnalyst Tool using a contour interval of 0.3048 (meters).
The resultant isolines' meter elevations were then multiplied by 3.28084 in a new field to display the elevations with a vertical resolution of 1.0 footAnalytic contour polylines were generated from the raster DTM surface. These may have a complex appearance and be difficult to interpret, but were chosen In order to best preserve the accuracy and precision of the data.
- Contours were then generated as polylines at 1-foot intervals with an index contour at every 10-foot interval.
- Depressed contours were not distinguished.
- The contour lines have elevation attribute values in both meters and feet.
- The lines may have been simplified slightly to remove any unnecessary vertices, and to reduce file size.
- Small, isolated contours may have been deleted to improve readability.
- Spot elevations (on tops, saddles, depressions or highest, lowest, turn back contours) were not added.
- No additional breaklines for retaining walls, roads or other features were incorporated..
- Topology was not validated.
Attributes
The layer's arc attribute table has the following fields:
| Field Name | Width | Output | Type | Description |
|---|---|---|---|---|
| ELEV_M | 4 | 5 | B | Elevation above or below sea level, in meters |
| ELEV_FT | 4 | 5 | B | Elevation above or below sea level, in feet |
| INDEX | 1 | 1 | T | Indicates whether or not a contour line is an index line for symbology and labeling options. The Indexed Contour Interval used in Geoprocessing was 3.048 meters (10 feet). This resulted in the "Type" Field having a value of 2 (index contour) for lines with elevations evenly divisible by 3.048 meters. Other lines had a "Type" value of 1. These values were converted to Y or N (text), indicating whether a line is an index contour line. |
Maintenance
As additional QL1 data become available and staff time permits, MassGIS may create 1-foot contours for additional areas in the state.