Pennsylvania Spatial Data Access

Abstract:

High resolution land cover dataset for Philadelphia. Seven land cover classes were mapped: (1) tree canopy, (2) grass/shrub, (3) bare earth, (4) water, (5) buildings, (6) roads, and (7) other paved surfaces. The minimum mapping unit for the delineation of features was set at ten square feet. The primary sources used to derive this land cover layer were 2008 Orthophotography and 2008 LiDAR LAS data. Ancillary data sources included GIS data (building footprints, road polygons, and hydrography) provided by City of Philadelphia. This land cover dataset is considered current as of 2008. Object-based image analysis techniques (OBIA) were employed to extract land cover information using the best available remotely sensed and vector GIS datasets. OBIA systems work by grouping pixels into meaningful objects based on their spectral and spatial properties, while taking into account boundaries imposed by existing vector datasets. Within the OBIA environment a rule-based expert system was designed to effectively mimic the process of manual image analysis by incorporating the elements of image interpretation (color/tone, texture, pattern, location, size, and shape) into the classification process. A series of morphological procedures were employed to insure that the end product is both accurate and cartographically pleasing. No accuracy assessment was conducted, but the dataset was subject to a thorough manual quality control. More than 30700 corrections were made to the classification.

Purpose:

This dataset was developed as part of the Urban Tree Canopy (UTC) Assessment for Philadelphia. As such, it represents a 'top down' mapping perspective in which tree canopy over hanging other features is assigned to the tree canopy class. At the time of its creation this dataset represents the most detailed and accurate land cover dataset for the area.

Supplemental_Information:

This project was funded by the City of Philadelphia. The methods used were developed by the University of Vermont Spatial Analysis Laboratory with funding from the USDA Forest Service.

Currentness_Reference:

ground condition

Use_Constraints:

None

Address:

81 Carrigan Drive

Address:

Aiken Room 220

Data_Set_Credit:

University of Vermont Spatial Analysis Laboratory

Attribute_Accuracy_Report:

No accuracy assessment was conducted, but the dataset was subject to a thorough manual quality control (QC).  30700 corrections were made to the classification.  Accuracy assessments from previous UTC land cover datasets indicate that the use OBIA techniques in combination with a detailed QC yield an overall accuracy of 95% or better.

Logical_Consistency_Report:

Valid raster dataset.

Completeness_Report:

Complete for Philadelphia based on 2010 boundary.

Horizontal_Positional_Accuracy_Report:

Unknown

Source_Contribution:

building footprints, road polygons, and hydrography

Source_Contribution:

elevation and statistical surfaces

Process_Description:

Object based image analysis (OBIA) using a rule-based expert system

Process_Description:

Manual corrections to land cover classification

Process_Description:

Metadata imported.

Process_Description:

Metadata imported.

Attribute_Definition:

Internal feature number.

Attribute_Definition_Source:

ESRI

Attribute_Definition:

Land cover code

Attribute_Definition_Source:

UTC