Symbolizing only most current events

Conditions préalables :

Before executing this procedure, you must have a tracking layer in your map document, and the tracking layer must have an appropriate track ID defined. If the tracking layer does not have an appropriate track ID defined, you will not get the expected results from following this procedure. You can set or change the track ID for a tracking layer on the Time tab of the Layer Properties dialog box.

Showing only the most current event for each track in a tracking layer is useful if you are concerned with only the current locations of objects. For example, if you are monitoring a fleet of vehicles in real-time, you might only be concerned with where the vehicles are right now.

Etapes :

1. Double-click the tracking layer in the Table of Contents window to open the Layer Properties dialog box. Click the Time tab.
2. In the Choose temporal settings list box, select Events.

   By default, the Display all events in the layer button is selected. This indicates that all events in the layer are being displayed. Of course, time windows and the current time being displayed also influence whether events are displayed at any given time.

3. Click the Display only the most current events in the layer button.

   This setting indicates that only the most current event for each track in the tracking layer will be displayed. If the tracking layer does not have a track ID defined, it does not have tracks, and this setting will result in nothing being displayed on the map.

   As shown in the diagram, track lines for the tracking layer will still appear on the map if they are turned on. However, track lines will be shortened to the length of any time window you have set for the tracking layer.

4. Click OK to save your changes and close the Layer Properties dialog box.

When you play back this tracking layer using Playback Manager, only the most current event for each track is displayed at any given time. For real-time tracking layers, only the most current position for each tracked object is displayed on the map.

Approfondissement :

While in real-time mode and under most circumstances in playback mode, Tracking Analyst only displays events that occurred in the past. The Display Future Events option in the user interface above can be used to display events that exist in the future. This can be useful if you are dealing with sensitive real-time data and you want to make sure that no events are hidden from the display due to your system clock being out of sync with the time stamps contained in data streaming in from your tracking service.

This option can also be useful if you are working with fixed-time data that has time stamps in the future. For example, you might have a dataset containing the projected locations of satellites in the future. Normally, this future data would not appear if Playback Manager is closed (and therefore Tracking Analyst is in real-time mode), and this can cause confusion. Checking the Display Future Events check box makes all your future data appear when Playback Manager is closed. In playback mode, your future data appears based on the current time set by Playback Manager.