2.0 Spatial Reference and Metadata
2.1 Projection and coordinate system standards
All layers conform to the spatial reference standards where appropriate unless otherwise
specified. The Pennsylvania State Plane coordinate system should be used. The
Pennsylvania State Plane coordinate system minimizes scale distortions within
Pennsylvania by implementing two state plane zones: north and south. The zones follow
county boundaries roughly midway across the state. No county is divided by a zone.
The Pennsylvania State Plane coordinate system provides a planar coordinate system for
surveyors, alleviating the need to work with spherical coordinates. This, in turn,
facilitates updates of property boundary surveys from the surveying community.
The General Assembly of Pennsylvania session of 1992 adopted an amendment to the
Act of June 2, 1937 (Public Law 1208, No 310). The amendment, titled Pennsylvania
Coordinate System Law - Omnibus Amendment, stipulates the Pennsylvania State Plane
Coordinate System, North American Datum 1983, with coordinate units in meters will be
used for all mapping completed after December 31, 1995. However, governments and the
general public within the Commonwealth continue to use English measures. In
Pennsylvania, the surveying community uses the US Survey Foot. A US Survey foot
equals 1,200 / 3,937 of a meter.
The map projection parameters for the Pennsylvania North Zone are:
1)
2)
3)
4)
5)
6)
7)
Lambert Conformal Conic
Standard Parallel: 40o 53’ (.883333)
Standard Parallel: 41o 57’ (.950000)
Longitude of Central Meridian: 77o 45’
Latitude of Projection Origin: 40o 10’
False Easting: 2,000,000 ft
False Northing: 0
The map projection parameters for the Pennsylvania South Zone are:
1) Lambert Conformal Conic
2) Standard Parallel: 39o 56’ (.93333)
3) Standard Parallel: 40o 58’ (.96666)
4) Longitude of Central Meridian: 77o 45’
5) Latitude of Projection Origin: 39o 20’
6) False Easting: 2,000,000 ft
7) False Northing: 0
The sixty-seven (67) counties in Pennsylvania are divided into North and South Zones as
follows:
Pennsylvania North Zone Counties (31)
Pennsylvania South Zone Counties (36)
Bradford
Cameron
Carbon
Centre
Clarion
Clearfield
Clinton
Columbia
Crawford
Elk
Erie
Forest
Jefferson
Lackawanna
Luzerne
Lycoming
McKean
Mercer
Monroe
Montour
Northumberland
Pike
Potter
Sullivan
Susquehanna
Tioga
Union
Venango
Warren
Wayne
Wyoming
Adams
Allegheny
Armstrong
Beaver
Bedford
Berks
Blair
Bucks
Butler
Cambria
Chester
Cumberland
Dauphin
Delaware
Fayette
Franklin
Fulton
Greene
Huntingdon
Indiana
Juniata
Lancaster
Lawerence
Lebanon
Lehigh
Mifflin
Montgomery
Northampton
Perry
Philadelphia
Schuylkill
Snyder
Somerset
Washington
Westmoreland
York
The map projection parameters for all spatial data sets must be fully documented
according to the Content Standard for Spatial Metadata as defined by the Federal
Geographic Data Committee (FGDC). Refer to the metadata section of this document for
additional details.
2.2 Tiling scheme
Orthoimagery and elevation data will be organized into an index comprised of ten
thousand foot square tiles forming a grid across the Commonwealth. Two such grids are
constructed: one for the State Plane Pennsylvania North Zone and one for the State Plane
Pennsylvania South Zone. Each tile will be named and numbered from the zero, zero
coordinate of the respective zone. This grid layout includes a total of approximately
8,400 tiles. There is no overlap of data or imagery across tile edges. Imagery and data
will fill an area tile; there will be no partial tiles.
For larger scale, finer resolution orthoimagery development (i.e. 1”=100’, 1’ pixel or
1”=50”, .5’ pixel), a nested tiling schema based on the 10,000’x 10,000’ tiling system
will be employed. For 1’=100’, 1’ pixel orthoimagery a nested tile schema would suggest
tiles measuring 5,000’ x 5,000’. For 1”=50’, .5’ pixel, a nested schema would suggest
2,500’ x 2,500’. The PAMAP Program office should be consulted for nested tiling
naming conventions.
The approximate tile count of 8,400 does not include additional tiles that must be
developed in the transition area between the Pennsylvania State Plane coordinate
system’s northern and southern zones. In this area, there will be an overlap of tiles in the
respective state plane zone by an amount to be determined. Due to the fact that all
production blocks have yet to be defined, the precise number of overlapping tiles is not
known. When determined, this number will be added to this plan once it is finalized.
DOI filenames should be derived from the northwest corner of each ortho tile using the
first four digits of the northing and easting coordinates referenced to the Pennsylvania
State Plane coordinate system, followed by the State designator “PA”, and the State Plane
zone designator “S”.
For example: yyyyxxxxPAS
Where:
yyyy = first 4 coordinates, northing
xxxx = first 4 coordinates, easting
PA = State Designator
S = Pennsylvania South Zone designator
The following figures illustrate the tiling scheme and counties for both north and south
zones.
Figure 2.21. North Zone Tiling Scheme and Counties
Figure 2.22. South Zone Tiling Scheme and Counties
2.3 Metadata standard
2.3.1 Metadata Purpose
The purpose of metadata is to provide the user and data creator with documentation about
a piece or collection of data. Good metadata provides the “who, what, where, when, and
why” for spatial data. Metadata is the most critical element in effective data sharing and
in managing spatial data assets. Metadata can be used to track changes to data, identify
the data creator and contact, provide information on how data was created, and for what
purpose data was created.
2.3.2 GDC CSDGM Metadata standard
Metadata is information about the content, quality, condition, and other characteristics of
data. Metadata is a critical element in facilitating the exchange of data between
organizations and maintaining organizational memory of data assets. For this reason,
metadata should be created and maintained for all spatial data sets. Accuracy for each
data layer being shared needs to be disclosed; and the individual analyzing the shared
data needs to be able to verify that the data accuracy is appropriate for the announced
need.
The Federal Geographic Data Committee (FGDC) was formed to develop a standard for
creating metadata. All federal agencies that create spatial data sets are required to create
accompanying metadata conforming to the FGDC standard. The Content Standard for
Digital Geospatial Metadata (CSDGM) was developed by FGDC to provide a common
set of terminology and definitions for the documentation of digital geospatial data. The
standard establishes the names of data elements and compound elements (groups of data
elements) to be used for these purposes, the definitions of these compound elements and
data elements, and information about the values that are to be provided for the data
elements.
Since the creation of the FGDC CSDGM standard, activities to harmonize the
International Organization for Standardization (ISO) metadata standard ISO 19115 with
FGDC's CSDGM have been undertaken. Currently (2005), this process is under review.
For more information on the efforts at the Federal level to standardize metadata go to
http://www.fgdc.gov/metadata/meta_stand.html. However, the FGDC CSDGM standard
in its original form is still the primary and most commonly used standard for creating and
maintaining spatial metadata.
2.3.3 Metadata Format
The format for metadata files accompanying the transfer of GIS data includes:
1) XML (Extensible Markup Language)
2) Plain Text
3) HTML (Hyper-Text Markup Language)
Many GIS software programs now allow metadata to be created as part of the data
creation process and saved in a variety of formats. ESRI ArcCatalog is one example of
this type of software.
By using one of these metadata formats, distribution and importation of the metadata into
an organizational GIS is less complex. In addition, XML allows the data creator to more
easily manage and update their metadata.
2.3.4 Metadata Elements/Fields
The FGDC CSDGM standard has hundreds of primary fields that could potentially be
populated by a data creator. However, the most critical fields are those which provide the
organization or data creator with the most vital information. These primary fields are:
1)
2)
3)
4)
5)
6)
7)
Identification_Information
Data_Quality_Information
Spatial_Data_Organization_Information
Spatial_Reference_Information
Entity_and_Attribute_Information
Distribution_Information
Metadata_Reference_Information
Metadata Elements
Identification
Information
Data Quality Information
Spatial Data
Organization Information
Spatial Reference
Information
Entity and Attribute
Information
Description
Basic information about the dataset. Examples include title, geographic
area covered (spatial domain/bounding coordinates), currentness, theme
keywords/place keywords, use constraints/access constraints, contact
information for the data.
An assessment of the quality of the dataset. Examples include positional
and attribute accuracy, completeness, consistency, sources of information,
and methods used to produce the data.
The mechanism used to represent spatial information in the dataset.
Examples include the method used to represent spatial positions directly
(such as raster or vector) and indirectly (such as street addresses or county
codes) and the number of spatial objects in the dataset.
Description of the reference frame for, and means of encoding,
coordinates in the dataset. Examples include the name of and parameters
for map projections or grid coordinate systems, horizontal and vertical
datums, and the coordinate system resolution.
This is the data dictionary portion of the metadata. Information about the
content of the dataset, including the entity types and their attributes and
the domains from which attribute values may be assigned. Examples
include the names and definitions of features, attributes, and attribute
Metadata Elements
Description
values.
Distribution Information
Information about obtaining the dataset.
Metadata Reference
Information
Contact information of the individual creating the metadata, and the date
it was created. Examples include metadata date, metadata review date,
contact organization, contact person, contact position, contact address,
metadata standard name.
2.3.5 Themes in Geospatial Metadata
The topic codes from this list should be used to populate the “Theme_Keyword” field of
the FGDC metadata to provide a high-level controlled classification.
Topic Code
Description and Examples
Farming
Rearing of animals and/or cultivation of plants
Examples: agriculture, irrigation, herding, pests and diseases affecting
crops and livestock
Flora and/or fauna in natural environment
Examples: wildlife, vegetation, biological sciences, ecology, wilderness,
wetlands, habitat
Legal land descriptions
Examples: political and administrative boundaries
Processes and phenomena of the atmosphere
Examples: cloud cover, weather, climate, atmospheric conditions, climate
change, precipitation
Economic activities, conditions and employment
Examples: production, labor, revenue, commerce, industry, tourism and
ecotourism, forestry, fisheries, exploration and exploitation of resources
such as minerals, oil and gas
Height above or below sea level
Examples: altitude, bathymetry, digital elevation models, slope, derived
products
Environmental resources, protection and conservation
Examples: environmental pollution, waste storage and treatment, nature
reserves, landscape
Information pertaining to earth sciences
Examples: geology, minerals, landslides, soils, hydrogeology, erosion
Health, health services, human ecology, and safety
Examples: disease and illness, factors affecting health, hygiene, substance
abuse, mental and physical health, health services
Base maps
Biota
Boundaries
Climatology/Meteorolog
y/Atmosphere
Economy
Elevation
Environment
Geoscientific
Information
Health
Imagery/BaseMaps/Earth
Topic Code
Description and Examples
Cover
Examples: land cover, topographic maps, imagery, unclassified images,
annotations
Military bases, structures, activities
Examples: barracks, training grounds, military transportation, information
collection
Inland water features, drainage systems and their characteristics
Examples: rivers, lakes, water utilization plans, dams, currents, floods,
water quality
Positional information and services
Examples: addresses, geodetic networks, control points, postal zones,
place names
Features and characteristics of salt water bodies
Examples: tides, tidal waves, coastal information, reefs
Information used for appropriate actions for future use of the land
Examples: land use maps, zoning maps, cadastral surveys, land ownership
Characteristics of society and cultures
Examples: archaeology, education, demographic data, recreational areas
and activities, social impact assessments, crime and justice, census
information
Man-made construction
Examples: buildings, museums, churches, factories, housing, monuments,
ships, towers
Means and aids for conveying persons and/or goods
Examples: roads, airports/airstrips, shipping routes, tunnels, aeronautical
charts, railways
Energy, water and waste systems and communications infrastructure and
services
Examples: hydroelectricity, geothermal, water purification and
distribution, sewage collection and disposal, electricity and gas
distribution,, data communication, telecommunication, radio,
communication networks
Intelligence Military
Inland Waters
Location
Oceans
Planning/Cadastre
Society
Structure
Transportation
Utilities/Communication
Chapter 2 References
Information provided in this document was taken from Pennsylvania Spatial Data Access
metadata resources section http://www.pasda.psu.edu/metadata/index.shtml; from the
Federal Geographic Data Committee http://www.fgdc.gov/metadata/meta_stand.html;
and from other related sources.
For more information on metadata development in Pennsylvania, please contact
pasda@psu.edu.