- quadrangle (quad)
-
See
topographic map.
- quadrant
-
A quarter of a circle
measured in units of 90 degrees.
- quadtree
-
A spatial index which
recursively decomposes a data set (e.g., image) into square cells of
different sizes until each cell has a homogeneous value. Quadtrees are
often used for storing raster data. See also
spatial indexing.
- quantize
-
To divide a continuum into
a series of discrete steps.
- query
-
See
map
query.
- radiometric resolution
-
The sensitivity the sensor
has for recording variations in the electromagnetic spectrum. Higher
values mean that more subtle appearance changes in the image can be
detected. .
-
A cellular data structure
composed of rows and columns for storing images. Groups of cells with the
same value represent features. See also
grid.
- raster/vector conversion
-
To convert data from raster
format to vector format with position and orientation selected by the
user. Also known as a raster-to-vector conversion, or vectorization.
- RAT
-
See route
attribute table.
- RDBMS
-
Relational database
management system. A database management system with the ability to access
data organized in tabular files that can be related to each other by a
common field (item). An RDBMS has the capability to recombine the data
items from different files, providing powerful tools for data usage. See
also relate.
- real numbers
-
Decimal numbers (e.g.,
3.1417, 0.25, 1.8992, 6.0).
- real time
-
Tasks or functions executed
so rapidly that the user gets an impression of continuous visual feedback.
- record
-
1. In an attribute table, a
single 'row' of thematic descriptors. In SQL terms, a record is analogous
to a tuple.
2. A logical unit of data
in a file. For example, there is one record in the ARC file for each arc
in a coverage.
- rectification
-
The process by which an
image or grid is converted from image coordinates to real-world
coordinates. Rectification typically involves rotation and scaling of grid
cells, and thus requires resampling of values.
-
The capability to ensure
that changes to one table that affect other tables are transmitted to
those other tables. For example, a table will not be given a
foreign key value that does not exist as a
primary key in another table.
-
A coverage feature class
used to represent a spatial feature as one or more polygons. Many regions
can be defined in a single coverage. Regions have attributes (PAT)
that describe the geographic feature they represent.
- registered table
-
A DBMS table which is part
of an ArcStorm database is said to be 'registered' with the database.
- registration
-
Process of registering
different themes to a common coordinate system or to one theme that is
used as a standard so that themes can be consistently overlaid.
-
An operation that
establishes a temporary connection between corresponding records in two
tables using an item common to both (i.e., relate key). Each record in one
table is connected to those records in the other table that share the same
value for the common item. Compare with relational
join.
-
The common set of columns
used to relate two attribute tables. See also relate,
primary key and
foreign key.
- relation
-
See
table.
- relational database
-
A method of structuring
data as collections of tables that are logically associated to each other
by shared attributes. Any data element can be found in a relation by
knowing the name of the table, the attribute (column) name, and the value
of the primary key. See also relate,
relate key, and relational join.
-
The operation of relating
and physically merging two attribute tables using their common item.
- relational operators
-
Phrases such as "greater
than," "less than," "maximum," "minimum," and "contains" that are used to
compare values associated with spatial data.
- remote sensing
-
The measurement and
recoding of information, data, or some property of an object or phenomenon
by a device that is not in physical contact with the object or phenomenon
being studied.
- resampling
-
The process of reducing
image data set size by representing a group of pixels with a single pixel.
Thus, pixel count is lowered, individual pixel size is increased, and
overall image geographic extent is retained. Resampled images are "coarse"
and have less information than the images from which they are taken.
Conversely, this process can also be executed in the reverse. In ArcInfo,
the GRID function RESAMPLE supports resampling of raster data using Cubic
Convolution, Bilinear Interpolation, Nearest Neighbor Assignment, and
custom "Nearest Data" assignment methods.
- resolution
-
1. Resolution is the
accuracy at which a given
map
scale can depict the location and shape of geographic features. The
larger the map scale, the higher the possible resolution. As map scale
decreases, resolution diminishes and feature boundaries must be smoothed,
simplified, or not shown at all. For example, small areas may have to be
represented as points.
2. Distance between sample
points in a lattice.
3. Size of the smallest
feature that can be represented in a surface.
4. The number of points in
x and y in a grid or lattice (e.g., the resolution of a U.S. Geological
Survey one-degree DEM is 1201 x 1201 mesh points).
- restore
-
To return a database to a
previous state by undoing all changes made since the given time. ArcStorm
provides a restore mechanism.
-
Root mean square error. A
measure calculated when registering a map to a digitizer, indicating the
discrepancy between known point locations and their digitized locations.
The lower the RMS error, the more accurate the digitizing or
transformation. See also
tic.
-
To cancel any changes to a
database made during the current transaction. Compare with
commit.
-
A feature class in ArcInfo
that is part of the route-system data model used to represent linear
features. Routes are based on an arc coverage and are defined as an
ordered set of sections. Because sections represent the portion of an arc
used in a route, routes do not have to begin or end at nodes. The
route attribute table (RAT) stores route attributes.
See also route-system and
route measure.
-
Route attribute table. An
RAT stores route attributes. There is one RAT for each route-system in a
coverage. In addition to user-defined attributes, an RAT contains a
sequence number and feature identifier for each route. See also
route-system, section,
SEC, and
feature attribute table.
-
A location along a route,
defined as a measure from a start point, where measures include distance,
time, milepost, address range. Measures are useful for locating
events along a route. There may be more than one start or end within a
route, in which case, the measures may not be unique within a
route-system. For example, there are many places that are within a
one-minute response time from a fire station.
-
A collection of routes
representing separate instances of a common linear entity, for example,
all school bus routes in a city. A single line coverage can contain many
route-systems, differentiated by name. For example, a road coverage can
contain a bus route-system, a highway route-system and a pizza delivery
route-system. Both an RAT and an SEC
exist for each route-system. See also
event.
- row
-
1. A record in an attribute
table. The horizontal dimension of a table composed of a set of columns
containing one data item each.
2. A horizontal group of
cells in a grid, or pixels in an image.
- RPC
-
A Remote Procedure Call
(RPC) is a communication mechanism which allows one UNIX process to
communicate with another UNIX process. These communicating processes can
be on different computers over a network. ArcStorm servers and clients use
RPCs to communicate with each other.
- rubber sheeting
-
A procedure to adjust
coverage features in a nonuniform manner.
Links representing from- and to-locations are used to define the
adjustment.
- run-length encoding
-
A data compression
technique for storing raster or gridded data. Run-length encoding stores
data by row. If two or more adjacent cells in a row have the same value,
the 'run' is recorded, as opposed to recording an individual value for
each cell. The more adjacent columns having the same value, the greater
the compression.
- satellite image
-
A picture of the earth
taken from an earth-orbital satellite. Satellite images may be produced
photographically or by on-board scanners (e.g., MSS).
- scale
-
See
map
scale.
- scale bar
-
A map element that shows
the map scale graphically.
- scanning
-
The process of capturing
data in raster format with a device called a
scanner. Some scanners also use software to convert raster data to vector
data.
- scratch file
-
A temporary file holding
intermediate data during an operation, such as when calculating arc
intersections, or building feature topology.
-
Spatial Data Transfer
Standard/Topological Vector Profile. A United States Federal standard
designed to support the transfer of different types of geographic and
cartographic spatial data. This standard specifies a structure and content
for spatially referenced data in order to facilitate data transfer between
dissimilar spatial database systems. TVP addresses a wide variety of
vector data types, models, and structures, as well as associated attribute
data. Also known as Federal Information Processing Standard (FIPS) 173.
-
Section table for the
section feature class in a coverage. The SEC holds attributes about
sections. In addition to user-defined attributes, the SEC contains
information on both the route number and arc number to which the section
belongs, the starting and ending positions expressed as percentages of the
arc length, starting and ending positions expressed as measures along the
route, an internal sequence number and a section feature identifier. See
also
feature attribute table.
-
A feature class in ArcInfo
that is a component of the route-system data
model used to implement routes. They form the
infrastructure of route-systems much like arcs form the infrastructure of
polygons. Sections are the arcs, or portions of arcs, used to define each
route. See also SEC.
-
A line on a surface
defining the position of a
profile.
- selection coverage
-
A coverage whose area
overlaps that of a map library. It identifies the area to extract data
from, or insert data into, a map library.
- semivariogram
-
A figure relating the
variance of the difference in value of an attribute at pairs of sample
points to separation distance.
- setuid
-
A process which can set its
effective user to super-user (root). That is, although any user can run
the process, the process can then execute operations which require root
privileges. One example of a setuid process is the ArcStorm wservice
process.
-
A pattern used to shade
polygons in ArcInfo. Shade symbol patterns include crosshatch, repeating,
and solid fill.
- SIF
-
Standard interchange
format, a spatial data exchange format. A standard or neutral format used
to move graphics files between computer systems.
-
Refers to a level of
coordinate accuracy based on the number of significant digits that can be
stored for each coordinate. Single-precision numbers store up to 7
significant digits for each coordinate, retaining a precision of 5 meters
in an extent of 1,000,000 meters. ArcInfo data sets can be stored as
either single- or double-precision coordinates. See also
double precision.
- sliver polygon
-
A small areal feature
commonly occurring along the borders of polygons following the
topological overlay of two or more coverages.
- slope
-
A measure of change in
surface value over distance, expressed in degrees or as a percentage. For
example, a rise of 2 meters over a distance of 100 meters describes a 2%
slope with an angle of 1.15. Mathematically, slope is referred to as the
first derivative of the surface.
- small scale
-
A map scale that covers a
relatively large area and has generalized labels. A large area of the
earth's surface on one page is a small-scale map (i.e., a 1:1,000,000 map
where 1 map unit equals 1,000,000 ground units is small scale compared
with a 1:500 map). Contrast with large scale.
- smoothing
-
A set of procedures for
removing short-range, erratic variation from lines, surfaces, or data
series.
- SNA
-
Systems network
architecture. Networking protocol popular in IBM environments.
- snapping
-
The process of moving a
feature to coincide exactly with coordinates of another feature within a
specified snapping distance, or tolerance.
- soft copy
-
A temporary image of a map
or diagram on the screen or a computer display.
- soundex
-
A phonetic spelling (up to
six characters) of a street name, used for address matching. Each of the
26 letters in the English alphabet are replaced with a letter in the
soundex equivalent:
English: A B C D E F G H I
J K L M N O P Q R S T U V W X Y Z
Soundex: A B C D A B C H A C C L M M A B C R C D A B W C A C
Where possible, geocoding
uses a soundex equivalent of street names for faster processing. During
geocoding, initial candidate street names are found using soundex, then
real names are compared and verified. See also
geocode.
- source code
-
A computer program that has
been written in an English-like computer language. It must be compiled to
yield the object code before it can be run on the computer.
- spaghetti digitizing
-
Refers to the digitizing of
map features without any initial regard to the sequence or identification
of line/point intersections.
-
The process of modeling,
examining, and interpreting
model results. Spatial analysis is useful for evaluating suitability
and capability, for estimating and predicting, and for interpreting and
understanding. There are four traditional types of spatial analysis:
topological overlay and contiguity analysis, surface analysis, linear
analysis, and raster analysis.
- spatial context
-
The relationships or
interactions that exist between various objects or phenomenon over a
specified distance.
- spatial data
-
Information about the
location and shape of, and relationships among, geographic features,
usually stored as coordinates and topology.
- spatial feature
-
See
geographic feature.
-
A means of accelerating
coverage drawing, spatial selection, and feature identification by
generating feature-based indexes for one or more feature classes of a
coverage.
- spatial interaction
-
An analytical technique
that estimates the number of
interactions occurring between an origin and destination locations.
The number of interactions is based on the properties of the origin to
produce a trip (production),
the destination's
attractiveness and the
impedance of the link between the two locations. The goal of spatial
interaction modeling is to be able to model and predict the number of
interactions occurring between populations for a particular type of
activity such as retailing.
-
Analytical procedures
applied with a GIS. There are three categories of spatial modeling
functions that can be applied to geographic features within a GIS: (1)
geometric models, such as calculating the Euclidean distance between
features, generating buffers, calculating areas and perimeters, and so on;
(2) coincidence models, such as
topological overlay; and (3) adjacency models (pathfinding,
redistricting, and allocation). All three model categories support
operations on spatial data such as points, lines, polygons, tins, and
grids. Functions are organized in a sequence of steps to derive the
desired information for analysis. See also
model and
analysis.
- spatial order
-
An index assigned to
features based on their relative closeness in two-dimensional space.
- spatial query
-
See
map
query.
- spatial resolution
-
The ability to sharply and
clearly define the extent or shape of features within an image. It
describes how close two features can be within an image and still be
resolved as unique..
- spectral resolution
-
The number and dimension of
individual wavelengths from the electromagnetic spectrum, which the sensor
can detect..
- spike
-
1. An overshoot line
created erroneously by a scanner and its rasterizing software.
2. An anomalous data point
that protrudes above or below an interpolated surface representing the
distribution of the value of an attribute over an area.
-
A mathematical curve used
to smoothly represent spatial variation. A spline operation inserts
vertices to create a curve in an arc. See also
grain tolerance and
densify.
- SPOT
-
1. An earth resource
satellite with high resolution sensors launched by France in January,
1986. 2. The generic name for a series of natural resource scanning
satellites launched by France.
- SQL
-
Structured Query Language.
A syntax for defining and manipulating data from a relational database.
Developed by IBM in the 1970s, it has become an industry standard for
query languages in most relational database management systems.
- SQL/MM
-
An international standards
effort, sponsored by ISO to extend SQL to support multimedia applications,
including access and manipulation of geographic data.
-
Standardized raster
graphic, a digital representation of a map or chart, which is captured by
automatic digitization (scanning), stored on a digital storage media, and
displayed on a raster screen or raster plotter; obtained by a regular scan
of a paper map or chart or repromat. It consists of a raster data set of
RGB intensities or colour (sic) codes.
- state plane coordinates
-
A system of x,y geographic
coordinates defined individually for each state. Locations are based on
the distance form a unique origin for each state or portion of a state.
- station file
-
An AML file containing
commands needed to establish the environment for graphic display and
graphic input. Typically, station files contain commands that define the
DISPLAY device, the AML &TERMINAL device, the type of DIGITIZER, if any,
and the method to be used for COORDINATE input.
- sterio pair
-
Two photographs having
sufficient perspective overlap to record parallax of detail to make
possible stereoscopic examination of an object of an area common to both
photographs. A three-dimensional perspective is provided.
-
Stops are locations visited
in a
path or
tour;
they may represent customers on a delivery route or cities in a highway
system. Stops and stop attributes are maintained in INFO files referred to
as stops files.
- stop impedance
-
The time it takes for a
stop transfer to occur. This is used to compute
the
impedance of a
path
or
tour.
-
The number of things or
packages transferred at a stop. This is used to find the total number of
transfers on a path or tour.
- string
-
A series of alphanumeric
characters of any length enclosed by quotes.
- subclass
-
A special
feature class in a coverage which allows many features of the same
class to be defined. Annotation, region, route-system, and section are
types of subclasses. For example, a road coverage may have three
route-systems stored as subclasses for mail delivery, street cleaning, and
garbage pickup.
- supply
-
The availability of
services or goods at
centers. An example of a type of supply is the availability of milk at
grocery stores, cars at a car dealer, or the number of movie screens at a
theater.
-
A geographic phenomenon
represented as a set of continuous data, such as elevation or air
temperature over an area. A clear or sharp break in values of the
phenomenon (breaklines) indicates a significant change in the structure of
the phenomenon (e.g., a cliff), not a change in geographic feature.
Surfaces can be represented by models built from regularly or irregularly
spaced sample points on the surface. See also
surface model.
-
Digital abstraction or
approximation of a surface. Because a surface contains an infinite number
of points, some subset of points must be used to represent the surface.
Each model contains a formalized data structure, rules, and x,y,z point
measurements that can be used to represent a surface. The TIN software
package supports two data models for representing surfaces:
lattice and
tin.
- SYBASE
-
A relational database
management system to which ArcInfo has access through the DATABASE
INTEGRATOR.
- symbol
-
A graphic pattern used to
represent a feature. For example, line symbols represent arc features;
marker symbols, points; shades symbols, polygons; and text symbols,
annotation. Many characteristics define symbols, including color, size,
angle, and pattern. See also
text symbol,
marker symbol, shade symbol, and
line symbol.
- symbol environment
-
Defines the types of map
symbols and their characteristics during a graphic display session in
ArcInfo. There are four types of active map symbols: line, marker, shade,
and text.
-
Tables which contain
information about a database, such as the data dictionary and database
transactions.