9. Plotting

Owned by Erlend Kvinnesland
Last updated: Dec 09, 2013
2 min read

Introduction

For various purposes - sooner or later you need maps, plots, images of the lines and surfaces you are generating. In Geocap there are various ways to obtain this. If you are only looking to export a graphical scene (screen shot), go to: Exporting Graphics.

Note that a lot of the documentation on plotting is found in-panel, either as separate help-buttons, in-panel text or as yellow-text appearing when the cursor is inside an element, e.g. a pulldown menu. Note the Help > Quick Guide to plotting with Geocap in the main panel.



In this section:

Basic Concepts

You may create PostScript plots in Geocap in many ways, e.g. by:

Creating Postscript files are done during a Postscript session. A Postscript session starts by specifying the Postscript file to create, and ends by closing the same file. During the session the filter may be turned on or off, and various Postscript commands may be executed. A terminated Postscript session can not be continued. Also, there is no undo or regret functionality. Output written to the Postscript file is permanent (but you may of course edit the Geocap script and re-run the generation of the Postscript file).

Creating the output is almost always a mapping from dataset coordinates to the Postscript viewport:

Dataset coordinates -> Postscript viewport

The user will be familiar with dataset coordinates, which is simply the x-y-z value range within which his dataset resides. In the current version of the PS-filter z values are ignored, and there is no transparency. Whatever is displayed last will be visible on top.

The viewport is a rectangular area of the paper, the size and location of which is determined by the user. The default size is the paper itself; in most cases the user will want to reduce this somewhat in order to obtain a margin. The main job of the Postscript filter is to scale, rotate and translate the dataset coordinates to match the viewport.

A distinction is made between VTK graphics and user generated graphics. VTK graphics correspond to the usual dataset, and will usually comprise the actual map. Commands that make the dataset visible on the screen will, if the Postscript filter is turned on, also direct the dataset through the Postscript filter and onto the Postscript viewport. Examples of shell commands are sma, map and acm. The Region Of Interest will be called the window (see psc win), and is a rectangular subset of the dataset that will be mapped. However, this is seldom enough to make a complete map. Consequently, the PS-filter provides additional functionality to create text and graphics primitives like text, lines, and axes onto the plot. Currently the mechanism that creates Postscript axes is different from the regular axe command.