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Geospatial overview
The purpose is to describe geospatial characteristics of resources. However, since geospatial searching can be challenging and computer intensive, geospatial information is layered in the framework. This layering will provide the appropriate level of search precision and the ability to expedite the return of search results based on how geospatially detailed library users wish to go. In addition, the information captured is consistent with information in other standard frameworks like FDGC and Dublin Core and the simple GIS community. Experts in library science, software engineering and geoscience from the Alexandria Digital Library, the Colorado School of Mines and the DLESE Program Center participated in the development of the framework's geospatial concepts over an 18 month period.
The geospatial characteristics captured in the framework are:
- Overarching bounding box - a single, overall, encompassing, geometric footprint on the surface of a planet or moon in our solar system; the geometric shape is a 4 vortex box that uses geographic latitude and longitude
- Detailed geometries - detailed geometric footprints (polygons, points and lines) on the surface of a planet or moon in our solar system by using multiple latitude and longitude tuples; an overarching bounding box is always required
- Elevation -the vertical minimum and vertical maximum, with reference to ground-level or a datum level, of geospatial footprints: the overarching bounding box and detailed geometries
- Planet or body - indicates what planet, moon or body in our solar system the geospatial footprints apply to
- Place-name tied to coordinates - the name of a location that is specified by a geospatial footprint, e.g. N= 41°, S= 37° E= -102°, W= -109° is Colorado, United States; can be used in geospatial and keyword searching
- Place-name not tied to coordinates - the name of a location that is not specified by a geospatial footprint; can only be used in keyword searching
- Event name tied to coordinates - an event that occurred within an area specified by a geospatial footprint, e.g. N= 45.0°, S= 22.0°, E= -62.0°, W= -86.0° is Hurricane Fran; can be used in geospatial and keyword searching
- Event name not tied to coordinates - an event that occurred within an area that is not specified by a geospatial footprint; can only be used in keyword searching
- Objects in space - the location of objects (e.g. nebulas), that are not within the solar system, described using the convention of right ascension, declination and epoch
- Coordinate system - the frame of reference specifying the location of an object in 'space'. Since DLESE uses overarching bounding boxes, the only allowed coordinate system is geographic latitude and longitude. Coordinate systems apply to visuals and raw and gridded data.
- Vertical and horizontal datum - a base reference
in a coordinate system; the initial point of origin and orientation of an
ellipsoid that models the Earth in the region of interest. Datums apply to
coordinate systems.
- Horizontal - NAD27, NAD83, ATS77
- Vertical - Sea level, CGD28-CDN, NAVD29-USA, NAVD88, IGLD88
- Global - WGS72, WGS84, PZ-90
- Other and Unknown are allowed values
- Projection - the systematic presentation (think 2-D map) of objects on the Earth or the celestial sphere using coordinate lines on a flat surface (different projection represent different parts of the Earth better, e.g. polar stereographic versus a satellite projection). Projection applies to visuals but not raw or gridded data until the data is represented on a 2-D map. Values of unknown, does not apply and other are allowed.
- Latitudes and longitudes - are in decimal degrees with south latitudes and west longitudes as negative values and north latitude and east longitudes as positive values.
The preprint article, Core Element of Digital Gazetteers: Placenames, Categories, and Footprints, by Linda Hill of the Alexandria Digital Library Project (last known link) suggests that search using just overarching bounding boxes is probably sufficient to meet most digital library user needs. However, it is the providers of geoscience data who often want more detailed geospatial information. Thus, this part of the framework accommodates this need by encoding detailed geometries. The geospatial section is not meant to describe data set variables or the content of numerical models.
Geospatial information is purposely separate from temporal information because it will have to be searched over separately. Secondly, most of the standard metadata frameworks keep geospatial and temporal information separate.
Further information
To see more detailed information about individual metadata fields, the allowed number of field occurrences, controlled vocabularies or XML structures, please refer to the desired version number of the framework on the left-side navigation menu and then go to the See in XML section.