There are several new technologies, which have resulted in changes to the type of control networks we need in Canada and how we use the networks. Probably the two most important are Geographical Information Systems or "GIS" and the Global Positioning System or "GPS".

The challenge for these information systems lies in the reference systems used to determine the position of the features.

Positioning data taken from a GPS receiver or other source and then fed into a GIS often comes from different sources and may relate to different reference systems.

That means roads may not necessarily line up, houses may appear to sit on roads and so on. To be useful, the positions of features entered into a GIS should not only be accurate, but also related to one another by using a common reference system such as the Canadian Spatial Reference System.

Geographic Information Systems

A Geographic Information System stores position information and the characteristics or "attributes" about features in a computer database and then displays the information or data digitally in different ways such as maps, tables and charts.

Attribute information describes the feature itself while position information tells us where it is located.

For example, in a GIS, we might have information about a series of trees that line a roadway in our neighborhood. For each tree, the GIS would have a position (latitude, longitude) plus descriptive information such as what type of tree it is, how high it is, whether it's healthy, etc.

GIS systems help us to manage all our resources including natural, physical, environmental and economical better.

GPS - The Global Positioning System

GPS offers the opportunity to position features quickly, easily and inexpensively using GPS receivers to track a series of GPS satellites orbiting the earth.

As the GPS receiver is held over a specific point, its position is determined and stored.

GPS can be used to provide positions and elevations quickly, accurately and relatively inexpensively.

New Technology vs. Older Control Networks

Restricting its use to older control networks would limit the benefits of new technology. The locations of the points that make up the existing control networks are often inconvenient for many applications. They may be:

• Too far from the project area thus expensive to use,
• Not GPS friendly, for example tree canopy or obstructions may prohibit GPS use, and
• Missing or have destroyed control markers, which are expensive to replace or to find an alternate marker.

New ideas and new tools are often needed to make the best use of new developments in technology.

The Active Control System, for example the Canadian Active Control System, is a result of new thinking. It supports the use of in meeting current and future needs of a rapidly growing positioning (activity of determining and using positions) and navigation community.