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  Engauge Digitizer - Glossary</H2>
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<DT>advanced import mode</DT>
<DD>The advanced Import mode offers the following advanced options for the imported file: 
floating axes and multiple coordinate systems. The advanced options
are only used by a small percentage of users and are therefore not made available during
the normal Import process. Once a file has been imported, the advanced mode settings cannot be
changed.</DD>
<DT>axes checker</DT>
<DD>Red box that briefly appears whenever the coordinate system has just changed. The red box
is drawn as a simple rectangle in cartesian coordinates, or as an annular arc in polar coordinates.
The axes checker can indicate when there is a mistake with the axis points, especially data entry errors
and accidental transposition. An axis point error usually makes the axes checker appear skewed.</DD>
<DT>axis point</DT>
<DD>Point that is added to a graph to define the scale. The two coordinate values must be defined
for each axis point. Three axis points are needed to define the scales in the two coordinate directions</DD>
<DT>checklist guide</DT>
<DD>List of steps to follow to digitize a graph, with checkmarks showing progress. This can be created 
during import, by running the checklist guide wizard.</DD>
<DT>checklist guide wizard</DT>
<DD>Wizard that can be used during import to create a checklist guide.</DD>
<DT>collinear</DT>
<DD>Collinear points lie along a straight line. The three axis points cannot
be collinear because graph coordinates are therefore impossible to compute.</DD>
<DT>collocated</DT>
<DD>Collocated points are close to each other or at the same location. Multiple axis points cannot
share the same location because graph coordinates are therefore impossible to compute,
and should be widely separated so computed graph coordinates are most accurate.</DD>
<DT>coordinate system</DT>
<DD>A coordinate system is defined by a pair of x and y axes. A graph with multiple coordinate systems
is digitized using the advanced <A HREF="answermultiplecoordsystems.html">Multiple Coordinate System</A> steps.</DD>
<DT>coordinates</DT>
<DD>Two values used in a graph to specify position. If the coordinates are cartesian, the 
two values are X and Y. If the coordinates are polar, the two values are the radius R and 
the angle theta. The X, Y and R coordinates can be logarithmic</DD>
<DT>corner</DT>
<DD>The point at the junction of two line segments in a piecewise linear curve</DD>
<DT>curve</DT>
<DD>Continuous line in a graph or map. This is digitized by creating curve points along the line</DD>
<DT>curve point</DT>
<DD>Point that is added to a graph on top of either a curve or point in the original image</DD>
<DT>digitize</DT>
<DD>Process of converting non-digital data into numbers. The specific type of digitizing performed 
by Engauge Digitizer is the conversion of graph and map images into numbers. These numbers can be 
exported to spreadsheets and other math software</DD>
<DT>discretize</DT>
<DD>Process that converts each pixel of an original image into either the black foreground, or 
the white background. The colors and grays of the original image are lost. By controlling
discretizing, unwanted parts of the original image can be removed</DD>
<DT>engauge</DT>
<DD>Process of converting an image file containing a graph or map into numbers. The word 'engauge' 
was invented to distinguish this process from other types of digitizing</DD>
<DT>export</DT>
<DD>Process of copying digitized information from Engauge Digitizer to other software
or a file</DD>
<DT>fast correlation</DT>
<DD>A preferred method of performing template matching, which is identifying various places
in an image where a template (or sample) appears. This method is fast because it uses a highly 
efficient <A HREF="http://www.fftw.org">Fast Fourier Transform</A>, and is 
therefore used by Engauge to perform point matching.</DD>
<DT>floating axis</DT>
<DD>A floating axis is an x axis with unknown y value, or y axis with unknown x value. A graph with a
floating axis is digitized according to <A HREF="answerfloatingaxes.html">Floating Axes</A>.</DD>
<DT>graph</DT>
<DD>Image that normally has one coordinate system consisting of two coordinate directions. Three 
axis points define the scales in the two coordinate 
directions, and the location of the origin. Graphs have either points or curves. An image may also
have multiple coordinate systems.</DD>
<DT>grid display</DT>
<DD>Grid lines may be added to a graph after the axis points have been defined. Any errors while
creating the axis points are usually apparent when grid lines are displayed</DD>
<DT>grid removal</DT>
<DD>Process that removes the grid from an original graph image so automated 
digitizing techniques perform better</DD>
<DT>import</DT>
<DD>Process of loading an original graph or map image into Engauge Digitizer</DD>
<DT>line graph</DT>
<DD>Graph containing lines</DD>
<DT>line segment</DT>
<DD>Part of a straight line that lies between two end points</DD>
<DT>map</DT>
<DD>Image without any coordinates, and having the same scale in any direction. A scale bar defines 
the scale in a map</DD>
<DT>measure</DT>
<DD>Set of one or more connected line segments that is used to measure distance and/or area
in a graph or map</DD>
<DT>piecewise linear</DT>
<DD>Curve that is composed of multiple line segments. A graph of the absolute value function is 
a simple example of a piecewise linear curve</DD>
<DT>point graph</DT>
<DD>Graph containing distinct points in the original image</DD>
<DT>point match</DT>
<DD>Automated digitizing technique used on graphs containing points. The user selects a
representative sample point, and then similar points are automatically digitized starting with the 
closest match</DD>
<DT>resolution</DT>
<DD>The distance in graph units corresponding to the pixel separation of the original image. This
distance is displayed in the status bar, since it represents the accuracy of the graph measurements</DD>
<DT>sample point</DT>
<DD>The point, chosen by the user during point matching, that best represents the points to be
matched</DD>
<DT>scale</DT>
<DD>Relationship between the actual distance on the graph or map, and the represented units. Typically,
actual distance is measured in pixels on the screen, or centimeters or inches on a printout. The
represented units may be distance, time, percent, counts, ...</DD>
<DT>scale bar</DT>
<DD>Line segment that defines the scale of a map</DD>
<DT>segment</DT>
<DD>Piece of a curve, in a graph, that can be automatically digitized using segment fill mode. A
segment is a set of adjoining points that lie between two endpoints</DD>
<DT>segment fill</DT>
<DD>Process of automatically digitizing a curve in a graph, by creating curve points along 
each segment along the curve</DD>
<DT>select mode</DT>
<DD>Digitizing mode in which existing points can be selected by clicking on an individual points,
or clicking and dragging to select all points in a box. Shift-click adds a new point to the points 
that are already selected. The control key temporarily hides points that do not belong to the
currently selected curve.</DD>
<DT>session</DT>
<DD>Period of time spent using Engauge Digitizer, from starting the software to stopping it</DD>
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