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northeast Wisconsin terrain model GPS satellite orbits Modis image - Aug 15, 2006
Cofrin Center for Biodiversity
Geospatial technology is a collective term for disciplines that use spatial referencing to facilitate compilation, manipulation, interpretation and display of data. "Spatial" in this case means location relative to the earth's surface - it's not about rocket ships and black holes. Remote sensing, photogrammetry and geographic information systems (GIS) are just a few examples of disciplines that fall under the geospatial technology umbrella.


Spatial Databases
Accomplishing work of any kind generally starts with an input of raw material. In the realm of geospatial technology the raw material is spatially referenced data stored in standardized computer file structures called spatial databases. Spatial databases are like "regular" databases in that they contain multiple elements (records) all using the same set of attributes to describe the "what is" aspect of each record. In other words they are thematic. In a spatial database, the "where is" aspect of a chunk of data is expressed in a well-defined numeric addressing system and fused together with the "what is" aspect. The computer files themselves conform to rigorous standards.

Accomplishing work also involves the use of tools. In geospatial technology, the primary tools are high-end database software that understands the spatial referencing information included in spatial databases. There are many legitimate data formats in the geospatial technology universe and many legitimate software packages. Here at UW-Green Bay, the predominant software tools are various components of ArcGIS, a geographic information system software suite published by Environmental Systems Research, Inc. (Esri). From a practical standpoint, a data file that can be read by ArcGIS qualifies as a true spatial database.

Spatial databases don't flow automatically from data-taking. Lots of very good data does not originate as true spatial databases and the work to upgrade it can be difficult and expensive. The database format must be selected and the earth model or datum (yes, there are several) must be defined. Often a two-dimensional grid is added to permit location to be recorded as displacements rather than as angles. Raw "where is" information, which can employ a variety of numeric and prose "languages", must be translated to the selected referencing scheme and the whole works must be packaged in compliance with the standards of the selected data format.

Is there a payback for all that effort? It would seem that the answer is "Yes". When location matters, standard spatial databases are the nearly universal vehicle for storing and publishing data. This allows much of the work in geospatial technology to be built on easily-obtained data published in ready-to-use formats. Not everyone is aware of the wide availability of spatial databases. The fact that various fields have their own terms for their spatially referenced data is somewhat to blame - think "satellite imagery", "digital line graphs", "gis layers", digital elevation models", etc.

There is plenty of good reference material on this topic - here are a few choice items:

Mapping Basics
The term "mapping" has several connotations in geospatial technology jargon. In the realm of spatial data, mapping refers to the attaching of spatial references to descriptive information to form spatial databases.

EXAMPLE - Our geospatial data library contains a "Brown County Street Centerlines" database. Each of the 26,000 records in the database corresponds to a street segment and contains values for a defined set of street attributes. There are 50 attributes in all - Name1, Name2, Type, SPEED_LIMIT to list a few. In addition to creating a table of attributes for the street segments, the authors mapped the street data - that is they embedded a string of coordinate pairs into each record that define the location of the street segment on the earth's surface.

When the author of a spatial database is selecting a referencing scheme, the simplest and most accurate choice is a geographic coordinate system (one that defines locations in terms of two angles - longitude and latitude). The earth is a three dimensional solid, why wouldn't you use a three dimensional referencing scheme? The concept is well-described in the article titled Latitude and Longitude published by the US Department of the Interior on their website. Check out the following for more info on this topic:
    •   Geographic Coordinates page on the website.

It turns out that there are many situations where it is preferable to map data to a 2-dimensional approximation of the earth's 3-dimensional surface. In this case the data author must select an appropriate projected coordinate system. The concept is well-described in the article (pdf) titled Map Projections published by the Michigan DNR. The first page in particular is an absolute gem of concise wordsmithing. Check out the following for more info on this topic:

Mapping - GPS and GNSS
Space-based navigation systems are a common data mapping tool. The old Global Positioning System (GPS) is familiar to many. Today the GPS program has been incorporated into the more comprehensive Global Navigation Satellite System (GNSS) program but the general idea is still the same - estimate location on the earth's surface by measuring distance to fast-moving objects 11,000 miles up. Check out the following for more info on this topic:
    •   GPS Mapping page on the Biodiversity Center website.
    •   Submeter GPS page on the Biodiversity Center website.

Authorship and Metadata
A spatial database is an academic and/or technical publication in the same sense as a journal article or reference book. When employing geospatial technology in an academic setting, literature searches should include a critical evaluation of the databases that will be used for reference. Data that is robust enough to use for reference generally comes with extensive authorship and methods information (metadata).

When we employ one of our computer software tools to organize and/or analyze spatially referenced data, we often become authors of one or more spatial databases ourselves. For our work to have lasting value, we need to develop and package it in accordance with published standards. We also need to document our work so that its useablility and robustness will be readily apparent to future users.