Glossary
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179
datum
Information about the interpretation of the Earth on which the coordinate sys-
tem is based. The datum can include the size and shape of the Earth (such as an ellipsoid
or flat map), origin point, orientation, and more. The datum is critical for accuracy,
because if a different datum is applied to a coordinate system, the coordinates will fall
onto different positions on the Earth.
decimal degrees
The mathematical representation of degrees in floating point values.
For example, in decimal degrees, 30
°
30'0" is 30.5
°
.
degrees
°
minutes' seconds"
The mathematical representation of degrees as minutes
and seconds, where one degree equals 60 minutes and one minute equals 60 seconds.
For example, in degrees
°
minutes' seconds", 30.5
°
is 30
°
30'0".
DGN file format
See
Microstation Design File.
digitize
To convert spatially dispersed information on maps, drawings, or charts into
machine-readable digital data that can be processed by computer software. Digitizing
captures spatial data as
XY
coordinates in digital form.
display range
The maximum and minimum scale at which Autodesk MapGuide will
display a layer. In Autodesk MapGuide Author, you can specify that a layer will display
only at certain ranges, or specify multiple display ranges for a layer and specify different
attribute styles for each of the display ranges, so that the layer will be drawn differently
depending on the current scale at which the map is displayed. By default, Autodesk
MapGuide displays the layer regardless of the current scale. See also
map scale
.
display styles
A set of properties that define how to display data on the layer. Layers
without themes typically have only one display style, which defines how to display all
of the data on the layer. Layers with themes typically have multiple display styles: one
for each category in the theme. You specify different properties for each display style,
such as color, fill style, line width, or point symbol. Display styles are defined for each
style set on a layer.
drive alias
A name for the location of drawings attached to an Autodesk Map project
drawing that replaces the traditional file path. Drive alias information is stored in the
Autodesk Map initialization file (
acadmap.ini
). Network users of Autodesk Map typically
assign the same drive alias to a network location when they share projects containing
attached source drawings. You create the aliases in Autodesk Map or by editing the
acadmap.ini
file. The
acadmap.ini
file is shared by all your Autodesk Map projects.
dynamic layer
A layer that gets data from Autodesk MapGuide Server as the user
zooms in and out on the map, turns the layer on and off, and so forth. Unlike static lay-
ers, which store all of the data for the entire layer in the MWF, dynamic layers download
only the data needed for the current view, so the dynamic option is better for layers with
large data sets or data that needs to be kept more secure.
ECW
See
Enhanced Compression Wavelet.
ellipsoid
An approximation of the Earth’s shape that does not account for variations
caused by non-uniform density of the Earth.
Enhanced Compression Wavelet (ECW)
Supported by ER Mapper, a wavelet-based
image compression format with high-quality results at high compression rates.
extents
The smallest rectangle that contains all features in a map, that is, the outer-
most boundaries of the map.
extranet
An intranet that is available to authorized users outside of the organization.
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