Database Query
RECLASS
-
- Reclassifies pixels by equal intervals or user-defined schemes.
RECLASS is commonly used as a database query routine by reclassifying
images into Boolean maps of areas meeting the specified conditions.
OVERLAY
-
- Undertakes pixel-wise addition, subtraction, multiplication,
division and exponentiation of paired images. Maximum, minimum,
-normalized ratio+ and -cover+ are also supported. On binary images,
logical AND and OR operations are supported by means of the multiply
and maximum operation. Other boolean operations are supported
through various binary image overlay combinations.
PCLASS
-
- Evaluates the probability that pixels exceed or are exceeded
by a specified threshold using the stated RMS error or the data
set and a normal probability distribution error model.
QUERY
-
- Extracts pixels designated by an independent mask into a sequential
file for subsequent statistical analysis.
AREA
-
- Creates a new image by giving each output pixel the value
of the area of the class to which the input pixel belonged. Output
can also be produced as a table or an attribute values file in
a range of measurement units.
PERIM
-
- Creates a new image by giving each output pixel the value
of the perimeter of the class to which the input pixel belongs.
Output can also be produced as a table or an attribute values
file in a range of measurement units.
see also ASSIGN (as an optional
reclassification routine), EXTRACT
, HISTO and CROSSTAB
.
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SCALAR
-
- Adds, subtracts, multiplies, divides and exponentiates pixels
by a constant value.
TRANSFOR
-
- Transforms the attributes of images such as log transformation,
using any of 14 operations.
see also OVERLAY .
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DISTANCE
-
- Calculates the distance/proximity of each pixel to the nearest
of a set of target pixels.
COST
-
- Generates a distance/proximity surface where distance is measured
as the least cost distance in moving over a friction surface.
VARCOST
-
- Computes an anisotropic cost surface. This module is the equivalent
of COST (specifically the COSTPUSH algorithm)
except that it recognizes that frictions may have different strengths
in different directions. Frictions are entered as force vectors
described by a pair of images - a magnitude image and a direction
image. VARCOST also allows the specification of an isotropic friction
image for omni-directional elements.
DISPERSE
-
- DISPERSE is a companion to VARCOST that
calculates dispersion distances. The procedure is essentially
the same as that of VARCOST except that
the emphasis is on forces acting to disperse a body (e. g., a
point-source contaminant spill) and the time taken to disperse
it to a specified distance. DISPERSE is released as an experimental
module in Version 4.1 and all users are invited to comment upon
their experiences with this procedure and provide suggestions
for modifications.
RESULTAN
-
- Computes the resultant force vector (as a magnitude and direction
image pair) from two input force vector image pairs.
DECOMP
-
- Decomposes a force vector (as a magnitude and direction image
pair) into X and Y component images. Also takes X and Y component
images and produces a force vector image pair.
SPDIST
-
- A companion to the DISTANCE module,
SPDIST calculates spherical distances on the surface of the earth
from designated features using spherical trigonometry.
PATHWAY
-
- Finds the shortest path between one or more specified points
and a destination specified as the lowest point on a cost surface.
ALLOCATE
-
- Performs spatial allocation using either DISTANCE
or COST surfaces.
THIESSEN
-
- Produces Thiessen polygons (a Voronoi Tesselation) about a
set of irregularly distributed points.
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SURFACE
-
- Produces slope gradient and aspect images from a surface.
Can also be used to create analytical hillshading.
GROUP
-
- Classifies pixels according to contiguous groups.
VIEWSHED
-
- Creates an image of all points visible from one or more viewpoints
over a given surface.
WATRSHED
-
- Determines the watersheds of one or more specified locations.
HNTRLAND
-
- Determines the supply areas dominated by, or the hinterlands
of, point demand centers.
see also FILTER .
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