General Comments, New Jersey 2012 Land Use/Land Cover Update Project

The 2012 updated land use/land cover (LU/LC), and impervious surface (IS) layer was mapped for the purpose of providing trend analysis data throughout the state. Aerial Information Systems, Inc., (AIS), Redlands, CA. performed all work under the direction of the New Jersey Department of Environmental Protection (NJDEP). The 2012 Land Use/Land Cover dataset is the fifth such data set that the NJDEP has produced. The initial land use/land cover layer was based on aerial photography captured in the spring of 1986. The second iteration of the land use data was based on photography captured in 1995, the third based on photography captured in the spring of 2002. The fourth, 2007, was based on photography captured in the spring of 2007. This latest update is based on photography captured in the spring of 2012. As with all previous layers, the 2012 data were produced by visually interpreting color infrared photography. Through this process, photo-interpreters examine each image, and based on their knowledge of photo signatures, classify the image into various land use/land cover categories. The classifications are converted into a land use/land cover GIS digital file, with each delineated polygon representing a distinct land use/land cover type.

All five land use/land cover data sets contain important land use data used in a wide variety of environmental analyses. Every effort has been made to insure that all land use data sets are as accurate as possible. However, note that these LULC data are intended to be used as resource data sets. Users of all data sets should refer to the links included below for more information that will help them understand the mapping process and appropriate uses and limitations of the data. Freshwater wetlands were first mapped under the New Jersey Freshwater Wetlands Mapping Program and were incorporated into the land use/land cover datasets. The wetlands delineations in these data are for screening purposes. The Land Use Regulatory Program (LURP) of the NJDEP determines the extent and final determination of wetlands in the State of New Jersey on a case by case basis.

Similar to the heads-up process used in the 1995, 2002 and the 2007 updates, the 2012 update was created by examining the existing 2007 LU/LC layer from the NJDEP GIS database over the spring 2012 color infrared digital imagery. Areas which had undergone no changes in the 2007 to 2012 time period simply have the 2007 codes moved into similar 2012 attribute fields. For those areas undergoing any changes, new line work and codes are added as needed to appropriately capture the change. As with the previous updates, these 2012 layers retain all of the codes and line work defining the 2007 ground conditions so that analyses between 2007 and 2012 can be done directly from the 2012 update layers.

Note that some modifications to the baseline 2007 data have been made during the 2012 update, as has occurred during the previous updates. There are several reasons for this. First, several new categories were mapped for the 2012 update: a Tidal Mud Flat (Water Type) code and a Disturbed Tidal Wetlands code. These were added to improve the tidal water delineations and identify tidal wetland disturbances. In addition, the Cowardin wetlands code, which was used in the original Freshwater Wetlands Mapping (FWW) program and added to the LU/LC data when the FWW polygons were integrated into the LU/LC data sets, was removed. While the Anderson classification codes have been updated as wetland polygons are updated in the LU/LC mapping, Cowardin codes have not been. So the legacy Cowardin codes may not accurately reflect the wetlands classification in the 2012 LU/LC layer, and to remove any confusion on wetlands classifications, the Cowardin code is not included in the 2012 data set. Note that removal of the Cowardin codes may result in some legacy wetland polygons being grouped together in the 2012 data set to reflect the Anderson classifications. (All original FWW mapping, however, is available as reference data in a separate data set.)

Second, there was an increased effort in this 2012 update to integrate the USGS National Hydrography Dataset Feature coding (FCodes) to water features. The water features from the LU/LC data sets, both the 2002 data and the 2007 data, were used to populate the New Jersey portion of the National Hydrography Database (NHD), which is a nation-wide database created by USGS to house all water features in the nation. NJDEP has taken over the stewardship of this important NHD data set, and is working to get the most detailed and accurate water feature data into the NHD system, and maintain all necessary NHD water codes. As such, some features coded as water in the 2012 data set may not appear to contain water on the 2012 imagery. But they retain the Anderson classification water codes, as well as a qualifying NHD water feature FCode which identifies these as, not only an artificial lake pond, but an intermittent reservoir associated with Stormwater basins. . In this effort, many additional water features previously unmapped were captured during this 2012 update.

Third, as has been the practice with previous updates, there are other instances throughout the data set where 2007 codes or line work have been adjusted before the 2012 edits were made. This is due in large part to having better imagery available that enables delineators to refine polygon classifications and line placements to more accurately map the landscape. These changes also affect the acreage values of many categories previously reported with the original 2007 data. For all of these reasons, note that category acreage values reported previously in the 2007 data set may differ from the values for the same categories when using the 2007 codes from the latest 2012 update.

The minimum mapping unit (mmu) of 1 acre has not changed for this update. Many of the water features are below mmu. With each update the LU/LC class delineation will improve to match new imagery and will likely be modified to meet the needs of the department.

As stated in this metadata record's Use Constraints section, 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. By downloading this data, user agrees to the data use constraints listed within this metadata record.

FINAL DELIVERABLES

NJDEP has adopted a watershed based management approach, so the data production was completed by USGS Hydrologic Unit Code (8 digit) also referred to as Subbasin or HU8. In previous updates watershed management area (WMA) were used.