![]() Examples of progressively varying continuous surface data are fluid and air movement. The second type of continuous surface data includes phenomena that progressively vary as they move across a surface from a source. Any representation of a surface is merely a sample (subset) of values from the total surface. For example, values for surface elevations are continuous across the entire surface. The attribute of the surface is stored as a z-value, a single variable in the vertical dimension associated with a given x,y location. Generally, the transition between possible values on a continuous surface is without abrupt or well-defined breaks between values. In contrast, continuous features are not spatially discrete. In addition, further analysis can be performed to define or identify new relationships among these features. Attributes can be assigned to the map features and used to describe, plot, symbolize, and label them. By now you have learned how the ArcGIS data structure represents the topological relationships of two-dimensional features. These data or map features are easily represented in maps as points, lines, or areas. There are definite changes in characteristics (such as owner name, parcel number, and legal area) between each feature on the map.Īn example of discrete features can be seen in this landownership map.ĭiscrete map features can also be thought of as thematic data. A landownership map shows the boundaries between various parcels. For example, a road has a width and length and is represented on a map as a line. This data can be represented as a continuous surface, generally without sharp or abrupt changes.ĭiscrete features are discontinuous and have definite feature boundaries. Surfaces are continuous data, such as elevation, rainfall, pollution concentration, and water tables. These types of data are represented by nominal, ordinal, interval, and ratio values. ![]() Most ArcGIS applications use discrete geographic information, such as landownership, soils classification, zoning, and land use. These include elevation (the fixed point being sea level) and aspect (the fixed point being direction: north, east, south, and west). One type of continuous surface data is derived from those characteristics that define a surface where each location is measured from a fixed registration point. ![]() Continuous data is also referred to as field, nondiscrete, or surface data. Discrete objects are usually nouns.Ĭontinuous data, or a continuous surface, represents phenomena where each location on the surface is a measure of the concentration level or its relationship from a fixed point in space or from an emitting source. Other examples of discrete objects include buildings, roads, and land parcels. Where the water's edge meets the land can be definitively established. A lake is a discrete object within the surrounding landscape. It is easy to define precisely where the object begins and ends. A discrete object has known and definable boundaries. Features and surfaces in ArcGIS can be represented as either discrete or continuous data.ĭiscrete data, also known as categorical or discontinuous data, mainly represents objects in both the feature and raster data storage systems. Values that are assigned to the cells of a surface can be represented as either discrete or continuous data.
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