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Selection of the Cartesian linear transformation with regular floating point coordinates
will result in a simple linear scaling of the input coordinates. The projection
is defined by stating
scale in inches/unit (-Jx) or axis length in inches (-JX)
If the y-scale or y-axis length is different from that of
the x-axis (which is most often the case), separate the two
scales (or lengths) by a slash, e.g., -Jx0.1i/0.5i or -JX8i/5i.
Thus, our data sets will plot as shown in Figure 5.1.
Figure 5.1:
Linear transformation of Cartesian coordinates.
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The complete commands given to produce this plot were
psxy -R0/100/0/10 -JX3i/1.5i -Ba20f10g10/a2f1g2WSne -W1p,- -P -K sqrt.d > GMT_linear.ps
psxy -R -JX -St0.075i -Glightgray -W -O sqrt.d10 >> GMT_linear.ps
Normally, the user's x-values will increase to the right
and the y-values will increase upwards. It should be noted
that in many situations it is desirable to have the direction of
positive coordinates be reversed. For example, when plotting
depth on the y-axis it makes more sense to have the positive
direction downwards. All that is required to reverse the sense of
positive direction is to supply a negative scale (or axis length).
Next: 5.1.1.2 Geographic coordinates
Up: 5.1.1 Cartesian Linear Transformation
Previous: 5.1.1 Cartesian Linear Transformation
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Paul Wessel
2004-10-01