Field (geography)
Encyclopedia
In the context of Spatial Analysis
, Geographic Information Systems, and Geographic Information Science
, the term field has been adopted from physics
, in which it denotes a quantity that can be theoretically assigned to any point of space, such as temperature or density. This use of field is synonymous with the spatially dependent variable that forms the foundation of geostatistics
and crossbreeding between these disciplines is common. Both scalar and vector fields are found in geographic applications, although the former is more common. The simplest formal model for a field is the function, which yields a single value given a point in space (i.e., t = f(x, y, z) )
Even though the basic concept of a field came from physics, geographers have developed independent theories, data models, and analytical methods. One reason for this apparent disconnect is that "geographic fields" tend to have a different fundamental nature than physical fields; that is, they have patterns similar to gravity and magnetism, but are in reality very different. Common types of geographic fields include:
Geographic fields can exist over a temporal domain as well as space. For example, temperature varies over time as well as location in space. In fact, many of the methods used in Time Geography
and similar spatiotemporal models treat the location of an individual as a function or field over time.
The single concept that underlies each of these methods is the concept of spatial dependence
or spatial autocorrelation, probably most succinctly expressed as Tobler's first law of geography
: "Everything is related to everything else, but near things are more related than distant things." Although it is more of a general tendency than a universal law, Tobler's Law (and the frequent exceptions to it) forms the basic language for understanding patterns in geographic fields.
This use of field should not be confused with that of computer science
and databases, which is also frequently used in geographic information systems.
Spatial analysis
Spatial analysis or spatial statistics includes any of the formal techniques which study entities using their topological, geometric, or geographic properties...
, Geographic Information Systems, and Geographic Information Science
Geographic Information Science
Geographic information science is the academic theory behind the development, use, and application of geographic information systems...
, the term field has been adopted from physics
Field (physics)
In physics, a field is a physical quantity associated with each point of spacetime. A field can be classified as a scalar field, a vector field, a spinor field, or a tensor field according to whether the value of the field at each point is a scalar, a vector, a spinor or, more generally, a tensor,...
, in which it denotes a quantity that can be theoretically assigned to any point of space, such as temperature or density. This use of field is synonymous with the spatially dependent variable that forms the foundation of geostatistics
Geostatistics
Geostatistics is a branch of statistics focusing on spatial or spatiotemporal datasets. Developed originally to predict probability distributions of ore grades for mining operations, it is currently applied in diverse disciplines including petroleum geology, hydrogeology, hydrology, meteorology,...
and crossbreeding between these disciplines is common. Both scalar and vector fields are found in geographic applications, although the former is more common. The simplest formal model for a field is the function, which yields a single value given a point in space (i.e., t = f(x, y, z) )
Even though the basic concept of a field came from physics, geographers have developed independent theories, data models, and analytical methods. One reason for this apparent disconnect is that "geographic fields" tend to have a different fundamental nature than physical fields; that is, they have patterns similar to gravity and magnetism, but are in reality very different. Common types of geographic fields include:
- Natural fields, properties of matter that are formed at scales below that of human perception, such as temperature or soil moisture.
- Artificial or aggregate fields, statistically constructed properties of aggregate groups of individuals, such as population density.
- Fields of potential, which measure conceptual, non-material quantities (and are thus most closely related to the fields of physics), such as the probability that a person at any given location will prefer to use a particular facility (e.g. a grocery store).
Geographic fields can exist over a temporal domain as well as space. For example, temperature varies over time as well as location in space. In fact, many of the methods used in Time Geography
Time geography
Time geography or time-space geography traces its roots back to the Swedish geographer Torsten Hägerstrand who stressed the temporal factor in spatial human activities. The time-space path, devised by Hägerstrand, shows the movement of an individual in the spatial-temporal environment with the...
and similar spatiotemporal models treat the location of an individual as a function or field over time.
History and Methods
The modeling and analysis of fields in geographic applications was developed in five essentially separate movements, which have gradually been integrated in recent years.- The quantitative revolutionQuantitative revolutionIn the history of geography, the quantitative revolution [n] was one of the four major turning-points of modern geography -- the other three being environmental determinism, regional geography and critical geography)...
of geography, starting in the 1950s, and leading to the modern discipline of spatial analysisSpatial analysisSpatial analysis or spatial statistics includes any of the formal techniques which study entities using their topological, geometric, or geographic properties...
; especially techniques such as the gravity modelGravity modelGravity models are used in various social sciences to predict and describe certain behaviors that mimic gravitational interaction as described in Isaac Newton's law of gravity...
. - The development of rasterRaster graphicsIn computer graphics, a raster graphics image, or bitmap, is a data structure representing a generally rectangular grid of pixels, or points of color, viewable via a monitor, paper, or other display medium...
GIS models and software, starting with the Canadian Geographic Information SystemCanadian Geographic Information SystemsThe Canada Geographic Information System was developed in the 1960s and 1970s to assist in regulatory procedures of land-use management and resource monitoring. At that time, Canada was beginning to realize problems associated with its seemingly endless boundaries, in combination with natural...
in the 1960s. - The technique of cartographic modeling, pioneered by Ian McHargIan McHargIan L. McHarg was born in Clydebank, Scotland and became a landscape architect and a renowned writer on regional planning using natural systems. He was the founder of the department of landscape architecture at the University of Pennsylvania in the United States. His 1969 book Design with Nature...
in the 1960s and later formalized in a field-centric form by Dana Tomlin as map algebraMap algebraMap algebra is a simple and an elegant set based algebra for manipulating geographic data, proposed by Dr. Dana Tomlin in the early 1980s.It is a set of primitive operations in a Geographic Information System which allows two or more raster layers of similar dimensions to produce a new raster...
. - GeostatisticsGeostatisticsGeostatistics is a branch of statistics focusing on spatial or spatiotemporal datasets. Developed originally to predict probability distributions of ore grades for mining operations, it is currently applied in diverse disciplines including petroleum geology, hydrogeology, hydrology, meteorology,...
, which arose from geology starting in the 1950s. - Cartographic techniques for visualizing "statistical surfaces" (another synonym for fields), including choroplethChoropleth mapA choropleth map A choropleth map A choropleth map (Greek χώρος + πληθαίν:, ("area/region" + "multiply") is a thematic map in which areas are shaded or patterned in proportion to the measurement of the statistical variable being displayed on the map, such as population density or per-capita...
and isarithmic maps.
The single concept that underlies each of these methods is the concept of spatial dependence
Spatial dependence
In applications of statistics, spatial dependence is the existence of statistical dependence in a collection of random variables or a collection time series of random variables, each of which is associated with a different geographical location...
or spatial autocorrelation, probably most succinctly expressed as Tobler's first law of geography
First law of geography
The first law of geography according to Waldo Tobler is "Everything is related to everything else, but near things are more related than distant things."This observation is embedded in the gravity model of trip distribution...
: "Everything is related to everything else, but near things are more related than distant things." Although it is more of a general tendency than a universal law, Tobler's Law (and the frequent exceptions to it) forms the basic language for understanding patterns in geographic fields.
This use of field should not be confused with that of computer science
Field (computer science)
In computer science, data that has several parts can be divided into fields. Relational databases arrange data as sets of database records, also called rows. Each record consists of several fields; the fields of all records form the columns....
and databases, which is also frequently used in geographic information systems.