GIS Dictionary – Letter R

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– R –

Relational Database
A collection of data organized in two-dimensional tables consisting of named columns and (usually unique) rows.

Relief Map
A model of the ground as a it actually exists, showing the topography of the geographic area mapped.

Remote Sensing
The technique of collecting information from a distance. Most common mediums used are aerial photography and satellite imagery. Before the advent of photography, remote sensing was accomplished in such ways as information collection from air ballons. See: Remote-Sensing Technologies.

Remotely Sensed Data
Data collected from a distance usually acquired through remote sensing technologies such as satellite imagery.

Representational Fraction
Also referenced as R.F.  Scale indicated by a fraction and written with a numerator of unity.   For example, an R.F. of 1/10,000 means that one unit on the map equals 10,000 units on the ground.

Resolution
The amount of detail found in one pixel of the image. For example an image with one meter resolution means that each pixel in the image represents one square meter on the ground.

Right of Way
Land area providing legal right of passage, i.e., street right-of-way, railroad right-of-way, etc.

Root Mean Square Error
Determined by first calculating the Mean Square Error (MSE) which is achieved by: (1) calculating the square of the deviations of points from their true position, (2) summing up the measurement, (3) and then dividing by the total number of points.  To get the Root Mean Square Error, calculate the square root of the MSE.