I. Description of Data to be Provided.
The data provided herein are distributed subject to the following conditions and restrictions:
SUBJECT DATA LAYERS
For all data contained herein, NJDEP makes no representations of any kind, including, but not limited to, the warranties of merchantability or fitness for a particular use, nor are any such warranties to be implied with respect to the digital data layers furnished hereunder. NJDEP assumes no responsibility to maintain them in any manner or form.
II. Terms of Agreement
1. Digital data received from the NJDEP are to be used solely for internal purposes in the conduct of daily affairs.
2. The data are provided, as is, without warranty of any kind and the user is responsible for understanding the accuracy limitations of all digital data layers provided herein, as documented in the accompanying cross-reference files (see Section 1.14 CROSS-REFERENCE). Any reproduction or manipulation of the above data must ensure that the coordinate reference system remains intact.
3. Digital data received from the NJDEP may not be reproduced or redistributed for use by anyone without first obtaining written permission from the NJDEP. This clause is not intended to restrict distribution of printed mapped information produced from the digital data.
4. Any maps, publications, reports, or other documents produced as a result of this project that utilize NJDEP digital data will credit the NJDEP's Geographic Information System (GIS) as the source of the data with the following credit/disclaimer:
"This (map/publication/report) was developed using New Jersey Department of Environmental Protection Geographic Information System digital data, but this secondary product has not been verified by NJDEP and is not state-authorized."
5. Users shall require any independent contractor, hired to undertake work that will utilize digital data obtained from the NJDEP, to agree not to use, reproduce, or redistribute NJDEP GIS data for any purpose other than the specified contractual work.
All copies of NJDEP GIS data utilized by an independent contractor will be required to be returned to the original user at the close of such contractual work. Users hereby agree to abide by the use and reproduction conditions specified above and agree to hold any independent contractor to the same terms. By using data provided herein, the user acknowledges that terms and conditions have been read and that the user is bound by these criteria.
The horizontal accuracy of the soundings is within a radius of 1.5 mm of the sounding location at the scale at which the soundings are recorded. NOS surveys are plotted at map scales that range from 1/10,000 for harbors and channels to 1/50,000 for open ocean surveys, with 1/20,000 being the most commonly used scale. The horizontal accuracy of the soundings is generally 30 m, but it can vary from as fine as 15 m in ports and estuaries to as coarse as 75 m in the offshore areas. Differential GPS has improved this level of accuracy considerably for the most recent survey data.
The vertical accuracy of the soundings is 0.3 m in 0 - 20 m of water, 1.0 m in 20 - 100 m of water, and 1% of the water depth in 100 m of water.
The xyz ASCII table was processed at NJGS by converting the longitude and latitude locations to easting, northing, NJ State Plane Feet NAD83 by using the New Jersey Geological Survey, Coordinate Conversion Utility program available at <http://www.state.nj.us/dep/njgs/geodata/dgs03-1.htm>. The NJGS Coordinate Conversion Utility accepts only ID, x and y fields. A subset table was created with ID, x and y fields for the conversion. After the conversion from longitude and latitude to easting and northing the table contained the fields ID, easting and northing. This subset table was then joined with the original xyz ASCII table by the ID field. A new field called elevation was added to this table to convert the elevations from meters to feet. The feet were derived by multiplying the water depth in meters by 3.28083, the number of feet in a meter to populate the elevation column with values in feet. The conversion from meters to feet was done to allow for volumetric calculations in cubic yards. The field containing the elevations in meters was removed.
The ASCII table with the columns ID, northing, easting and elevation was imported into Surfer (Version, 8.02 Golden Software, Inc., <http://www.goldensoftware.com>). These bathymetric elevations in feet from the ASCII table were gridded (Kriging) in Surfer with a 100 by 100 foot cell size (evenly spaced samples). Kriging in Surfer with 100 by 100 foot cell size provided the most accurate representation of the ocean depth in NJGS trials. After the gridding process was complete a contour map was created in Surfer from the grid. The contour interval was set at ten feet and the smoothing level was set on low. This contour data was exported as an Autocad DXF file.
The DXF file was imported into ArcGIS and saved as a shapefile. In ArcGIS, a twenty mile buffer was created from a shapefile of the New Jersey coastline. The bathymetric elevation contours off New Jersey shapefile was then clipped to this buffer file. Heads up editng was used to remove obvious errors. The erase command was used to remove any contours crossing over from the ocean into the inlets.