Thursday, August 04, 2005

The Data Monitor in GTVx

The Data Monitor is a very powerful part of GTVx that has been somewhat under publicized since its introduction almost two years ago. The Data Monitor is not an application or a command; it is, instead, a very flexible toolkit providing a set of methods and events for creating an application that can track and/or monitor a few to a large number of items. You may say that you can do this already with session graphics (redlines) in GTVx today, and you probably can to some extent. The Data Monitor was designed to take you past some of the limitations redlines pose in a dynamic environment and provide a richer feature set specifically for items that are not permanent or are constantly changing. Redlines were meant to be stored while Data Monitor items are not stored since they are derived for some existing set of information; thus, Data Monitor performance in regard to adding, deleted, and manipulating is somewhat greater than that of redlines and better support an environment of many constantly changing items for a large number of items.

What can the Data Monitor be used for? Ideally, the Data Monitor can be used with information that has many items with geographical positions, data that changes frequently (either moved, added, or deleted), and data that is temporary (session based versus long term). There are a few applications that should immediately spring to mind:

  • Lightning Strike Monitor – lightning strikes are many, constantly accumulating, and have little meaning after time. The strikes can be represented as Data Monitor Items that can be numerous and while they don’t move, their importance decays with time and can be reflected by their symbology.
  • Outage Management – show calls or trouble facilities in relationship to the GIS data. Calls are session oriented as they are constantly added and eventually deleted. Data Monitor Items can show both call locations, suspected facilities, and duration of outage (by symbology), and other information as tooltips.
  • Vehicle Tracking - show trucks or crews in relationship to the GIS data. The trucks can be moving so their position can change frequently. Trucks can be represented as Data Monitor Items and can carry information such as the crew information, next destination, and status in the form of a tooltip.

These are just a few examples of what the Data Monitor can be used for. Many of the Data Monitor features directly support these types of application:

  • A Data Monitor Item can be a bitmap image, a line, or a shape.
  • A Data Monitor Item can have a user-defined tooltip that displays just by hovering the cursor over the item. Tooltips can be modified when necessary to provide up to date information about the item.
  • Tooltips can be processed by the Data Monitor or Tooltip events can be fired letting the developer show or use the tooltip information.
  • A Data Monitor Item’s display characteristics are zoom level dependent. This feature is ideal for providing overall views of all data items with one set of display characteristics while providing a completely different display when viewing the items up close.
    Data Monitor Items fire events when the cursor hovers over them and when they are selected.
  • Data Monitor Items can be part of select sets and method are provided to select, unselect, and fence them for selection.

There are many useful application of the Data Monitor. Several examples are shown below:

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