74.2.3 Presenting Information Elements

To present information elements, you create information element themes (hereafter called IE themes). These govern the appearance of a marker that is plotted on the map. By varying its color, size, and shape, the marker can code the values of up to three numeric information elements. For example, you can have the marker color governed by RxLev and the marker size by RxQual, and use different symbols when the device is in idle mode, dedicated mode, and so on:

More generally, it is appropriate to use the color and size attributes for information elements with a continuous value range, and to use a suite of symbols for such things as status parameters having a small set of possible values.
The colors, sizes, and symbols used in the map are always the default ones for each information element, as set on the Info Element tab of the Navigator: see section "Info Element Tab". It is not possible to define these attributes differently in the map.
To create a new IE theme:

In the Theme Settings dialog, select one of the layers (or create a new layer to put the theme in: see section "Layers").

Click Add Theme:

System

Choose an information element category. See Information Elements and Events, chapter "Information Element Categories".

Mobile

Choose the device from which to pick the information element.

Offset (pixels)

This setting decides how far from its true position on the map the theme marker will be drawn. The offset direction is at right angles to the direction of travel; a positive offset is to the right relative to the direction of travel. Using offsets enables you to display several routes side by side.

Color

In this section you specify a rule for the theme marker color:

Choose Range to have the color governed by an information element. Select an element, and select an argument if applicable.

Choose Fixed to use a fixed color. This means, of course, that the color will not carry any information.

Size

In this section you specify a rule for the theme marker size, in the same way as for the color. See above.

Symbol

In this section you specify a rule for choosing the shape of the theme marker, in the same way as for the color. If you choose Fixed, pick a font in the first combo box, then pick a symbol in the second.
The Fixed options are useful if you want to use an IE theme just for plotting the route, and not for showing measurement data. Uniform markers, for instance circles, will then be plotted along the route at the shortest possible time intervals (about factors influencing this updating rate, see section "Notes on Route Plotting and Updating" below). Note that some information elements are not updated this often.
Once the IE theme has been defined, it appears in the box in the Theme Settings dialog under the layer it belongs to.

74.2.3.1. Notes on Route Plotting and Updating

The updating frequency for IE themes is governed by a number of factors. A general rule is that new theme markers are drawn at most twice a second. Another basic fact to keep in mind is that the position of a theme marker does not necessarily correspond exactly to a pair of GPS or pinpointing coordinates.
Here is a summary of the factors that affect theme plotting and updating:

Interpolation. Map positions, whether delivered by a GPS or pinpointed, are constantly interpolated (linearly) to enable plotting at half-second intervals. However, whether markers are actually plotted at this rate depends on other circumstances. See below.

Arrival of new measurement data. A new theme marker is plotted only if a message with fresh data has been delivered by the measurement device. Updates will thus be less frequent in idle mode than in dedicated mode. Note also that certain information elements are not updated regularly at all but only on special occasions (for example, when the device switches to a different RAB). If you want to plot such an IE with high frequency, include another IE that is frequently updated in the same theme.

Loss of positioning data. If GPS data is lost for an extended period of time (for instance while driving through a tunnel) but GPS coverage is eventually regained, positions will still be interpolated and plotted throughout the gap. On the other hand, if no more positioning data is obtained, interpolation is of course impossible, and no extrapolation of the route is attempted by TEMS Investigation.

Map zoom. The plotting density on the map is dependent on the current zoom of the Map window. When you zoom in, more markers are filled in to show the route in more detail; when you zoom out, markers are drawn more sparsely. Specifically, a new theme object (whether a symbol or a line) is drawn next to the latest one if the centers of the two objects will be more than 5 pixels apart on the screen.

Pin Pointing. The plotting of the routes between pin points is not done during logfile recording, information will only be displayed for the pin pointed spots. The route between them will be plotted (and visible) when replaying the logfile.