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Delaware River Basin Project

Modeling Urban Expansion in the Philadelphia Metropolitan Area; A Cellular Automata Approach

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Modeling Urban Expansion in the Philadelphia Metropolitan Area; A Cellular Automata Approach
Historical land-use data from the twentieth century was used as input to the SLEUTH land-use change model, a Cellular Automata model developed by Keith Clarke at the University of California at Santa Barbara, to produce projections of urban expansion in the Philadelphia metropolitan area.

Twentieth-Century Land Surface Changes in the Delaware Water Gap Basin, a GIS Snapshot Approach
Methods of integrating land-surface data and measuring change with time are being tested on historical land use/land cover data of the Delaware Water Gap watershed area in Pennsylvania.

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Home Study Area Land Cover Database Urban Growth Modeling Posters

Land Cover Database

Philadelphia Area

This study, which documents the human-induced land transformation of the region during the past 50 years, is dependent upon a temporal database of urban or built-up development, principal transportation, hydrography, and woodland land covers. The database provides a framework for GIS applications, urban growth modeling, and analyzing environmental impact analyses. Primary sources are USGS topographic maps and digital data.

The data directories are arranged by decade, thematic layer, and named after the 15-minute cell whose location is shown in the map above. The definition of the land cover type and the collection criteria of each are described below. The files available in .tif format, with accompanying .tfw world files. The Philadelphia project database is currently being checked for quality control; please contact us for any problems you may encounter.

The datafiles are available via ftp at:
https://thor-f5.er.usgs.gov/urban_dynamics/

The login is: anonymous
The password is: (your email address)

A paper describing the data collection techniques used for this database is provided as a PDF document (Download the free Adobe Reader).

Definitions

Urban or Built-up Land
Urban or built-up land is defined as areas characterized by buildings, asphalt, concrete, suburban gardens, and a systematic street pattern. Classes of urban development include residential, commercial, industrial, transportation, communications, utilities, and mixed urban. Political boundaries, such as city limits, are not used to define urban limits. Undeveloped land competely surrounded by developed areas, such as cemeteries, golf courses, and urban parks, is recognized within urban areas.

Principal Transportation
Principal transportation is defined as the roads, railroads, airports, and other transportation features that provide the infrastructure for urban development. The transportation data layer documents the evolution of principal transportation routes. Principal transportation routes form the network that supports the development of the urban core because such development requires the transport of people and materials.

Hydrography
Hydrography, which is defined as "open water bodies," includes streams, canals, rivers, lakes, reservoirs, bays, and estuaries. The hydrography data layer identifies streams at least 40 feet wide; ponds, lakes, and reservoirs covering at least 10 acres; and shoreline changes resulting from urbanization.

Woodland
Woodland, which is defined as "forest land," includes deciduous, evergreen, and mixed forest land, and orchards. The woodland data layer identifies deforestation or reforestation resulting from urbanization or conservation.

Collection Criteria

Urban or Built-Up Land
Urban or built-up land is compiled using criteria based on either urban tint, housing density, road density, spectral reflectance, or degree of land disturbance depending on the source materials. A residential density of three houses per 2.5 acres is defined as the minimum level of urban development. The extent of urban areas is determined by the existence of a dense systematic street pattern and the relative concentration of buildings. The minimum polygon width is defined as 1/10 mile or 528 feet.

Areas identified as urban or built-up are classified using the Land Use and Land Cover Classification System, USGS Professional Paper 964 (Anderson and others, 1976). The Anderson Level II classification definitions are modified to accommodate limitations in the historical source materials and to better categorize land use intensity. All urban or built-up areas will be collected as polygons and compiled into a separate coverage. Areas within the urban development are assigned to the Mixed Urban or Built-Up category 16. Areas with less intensive use, such as parks, cemeteries, golf courses, and undeveloped land are assigned to the Other Urban or Built-Up category 17.

The pink, purple, and gray tints depicted on the USGS maps represent dense residential areas where there were too many houses and other buildings to be individually symbolized. Tinted areas (pink, purple, and gray) are collected as Mixed Urban or Built-up category 16. Open, green, or white areas within the tint are collected as Other Urban or Built-Up category 17.

Linear residential developments are defined by a minimum width of 1/10 mile, minimum length of 1/2 mile, and a minimum density of 12 houses total, represented on both sides of the road. Nonlinear residential developments are defined by a systematic road network, a minimum of three houses in 2.5 acres, a main highway, and a community population of at least 500.

References: Acevedo, Tilley, and others, Developing a Temporal Database of Urban Development

Principal Transportation
The evolutionary development of a transportation system requires that implicit and explicit compilation criteria be defined to aid in creating a principal transportation data layer.

Implicit compilation criteria are based on various factors that together rate the quality of a transportation route. These factors are connectivity, lineage, mobility, and alignment:

*Connectivity is a measure that describes the level to which a route links urban centers or other modes of transportation, such as ports, railways, or airports.
*Lineage is a measure that describes the documented history of a route. It refers to the historical presence of a transportation route as depicted in literature or historical events.
*Mobility is a measure of the inherent road quality or design, which implies the level of service or accessibility for a particular route.
*Alignment is a measure of the rectilinear characteristics of a transportation route. One of the primary evolutionary features of roads has been based on the ability to straighten roads by overcoming geographic features that once were barriers to travel.

The presence of ancillary transportation features, such as bridges, tunnels, and ferries, is one of the factors that support the application of implicit compilation criteria. The presence and nature of the names applied to these routes also helps determine principal transportation routes. The descriptive title of these routes often provides insight into their use.

Explicit compilation criteria are based on the cartographic features used on maps that reveal the significance or effectiveness of a route. The advent of modern cartography and standardized approaches through feature classification and symbolization schemes have alleviated much of the dependence upon implicit compilation criteria. Roads designated as "interstates" by the Federal Highway Administration or as "Primary Highway, Class 1" on USGS maps meet the capture conditions.

The classification scheme adopted for primary transportation is a modification of the Anderson Level II, USGS Publications 964. All transportation features (roads and railroads) are linear except for airports, which are collected as point features. All roads will be compiled into a separate coverage and assigned category 1411. All railroads will be compiled into a separate coverage and assigned category 1421. All major airports will be compiled into a separate coverage and assigned category 1441.

References: Acevedo, Clark, and others, Development of the Temporal Transportation Database.

Anderson and others, 1976, USGS Publications 964.

Hydrography
The hydrography is compiled using criteria based on symbolization and size, depending on the source materials. The minimum mapping unit for hydrography is 10 acres. The classification scheme adopted for hydrography is a modification of the Anderson Level II classification system. All water bodies are collected as polygons, compiled into one separate coverage, and assigned category 55.

Woodland
The woodland is compiled using criteria based on tint and spectral reflectance. The minimum mapping unit for woodland is 10 acres. The classification scheme adopted for woodland is a modification of the Anderson Level II classification system. All woodland areas are collected as polygons, compiled into one separate coverage, and assigned category 44.

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