The 2012 Land Use Land Cover (LULC) update was performed using computer interactive heads-up digitizing techniques and ArcGIS software. The baseline datasets were year 2012 digital CIR orthophotos and the State’s existing 2007 LULC data. The data was digitally subdivided into working production modules based on the 1:24,000 scale USGS topographic quadrangle system. The LULC update was performed per the modified Anderson, et al., LULC classification and 2 acre minimum mapping unit (140’ width) established for the State’s previous LULC Update projects. The work was performed by Aerial Information Systems, Inc. (AIS) of Redlands, California.AIS staff analysts compared the State’s existing 2007 LULC data to the 2012 project imagery. Every polygon was reviewed for change, accuracy of polygon boundaries, and adherence to the 2012 LULC classification and mapping criteria. Polygon boundaries and codes were modified as necessary through the addition of new lines and codes or the modification of existing arcs. In addition, large obvious errors in the 2007 data were retroactively (‘retro”) corrected. The “retro” mapping process helps to ensure a more accurate baseline dataset for change analysis studies. The 2012 LULC interpretations were incorporated directly into the baseline 2007 LULC coverage to create a final composite coverage containing LULC information for both eras. Each polygon in the composite coverage was assigned an item for 2012 and 2007. Where no LULC change had occurred, the LULC class for both item years remained the same. Where a LULC change did occur, new boundaries were added to the data set as needed, subdividing the existing 2007 polygon, and the polygons were attributed for the appropriate 2012 LULC type. This method ensured that the different layers seamlessly co-registered to each other, creating a sliver free coverage for use in change analysis studies.

Revised 2007 LULC based on re-interpretation by AIS using the 2007 Aerial Imagery. This revision was part of the contract to update the 2012 LULC for the State of Delaware. Many errors were detected in the 2007 LULC interpretation and AIS provided correction for those errors.

This digital geospatial dataset represents land use land cover polygons as defined by the Delaware Modified Anderson System derived from: A Land Use and Land Cover Classification System for Use with Remote Sensor Data, U. S. Geological Survey Professional Paper 964, 1976; edited by Delaware in 2007, and 2012. The LULC update was performed using ArcGIS software tools, coding menus, and interactive photo-interpretative mapping techniques. Three relevant fields are included in the dataset attribute table:

• “LULC_CODE2017” – Delaware Modified Anderson System numeric code per 2017 polygons

• “LULC_CATEGORY2017” – Delaware Modified Anderson System category description per 2017 polygons

• “LULC_CATEGORY2017_CONDENSED” - Delaware Modified Anderson System category description per 2017 polygons with reduced number of selected categories for enhanced viewing and comprehension.

• “NCC_RES_DENSITY2017” - Additional residential density classes applied specifically to New Castle County as follows:

1 = Very Low Density Residential 5 - 20 acre lots, based on parcel use categories

2 = Low Density Residential 5 - 0.5 acre lot

3 = Medium Density Residential 2 du/acre - 8 du/acre (0.5 - .125 acre lot)

4 = High Density Residential >8 du/acre (<.125 acre lot)

• “LULC_CODE2012” – Delaware Modified Anderson System numeric code per 2012 polygons

• “LULC_CATEGORY2012” – Delaware Modified Anderson System category description per 2012 polygons.

This metadata record describes the creation of a 2007 update of the 2002 Land Use and Land Cover data set for the State of Delaware. The land use update was based on aerial imagery collected in the summer of 2007. The imagery was collected with 4 bands: B, G, R, and NIR. The update was performed using statistical differencing techniques to identify changed areas. Areas of change were photointerpreted by an analyst. The work was performed by the Sanborn Map Company, Inc. in Ann Arbor, Michigan.

The 2002 land use data were based on the 1997 land-use data of the State and 2002 false color infrared digital orthophotography at a scale of 1:2400.