User's Manual

UtiliNet® Endpoint User Guide 1-5-2007
Page 19 of 30
© Cellnet 2005
aesthetics. In the 900 MHz frequency band, antenna height provides the largest gain in terms of
RF distance. In general, the higher that antennas may be mounted the better.
3. Use topographical maps or computer prediction programs to plot paths between known nodes to
get an indication of the ability of radios to communicate with one another over the average terrain
in the area. This procedure provides an approximation for required antenna height in order to clear
obstructions that may exist in the paths.
4. If path profiles are generated that indicate that certain sites DO NOT have line-of-sight paths to
any other site, use general area maps to identify where repeater or additional router locations
might be needed to insure line-of-sight paths from every radio to at least one other radio.
5. Field Survey - Regardless of the quality of maps or computer databases, predictions are still just
predictions. The only way to insure RF connectivity, regardless of the product or the frequency, is
to test the path.
Calculating Latitude/Longitude Coordinates
Each radio in the UtiliNet network is programmed with a unique latitudinal and longitudinal (lat/long)
coordinate. These lat/long coordinates are used by the network to make logical routing decisions (see
"Network Routing" on page 9-2 for more information). Because the network uses the lat/long information
in a logical way, it is not necessarily important that the lat/long coordinates be physically accurate. What is
important, is that the lat/long coordinates of each radio be relatively correct to one another.
In other words, if each radio in a particular network was programmed with the same distance offset from
the actual physical location, network routing would not be adversely affected. However, if only a few of the
radios were programmed with the offset, routing could potentially suffer due to logical routing that does not
reflect the physical topology of the network. Therefore, it is not necessary for radios to have exact
coordinates. What is important, however, is that the method used to derive the lat/long coordinates be
capable of providing repeatable coordinate information which is physically relative and consistent system
wide.
Below are the most common, commercially available, methods of deriving latitude longitude information.
A brief analysis has been provided to compare and contrast the benefits of each.
• Global Positioning Systems
• United States Geological Survey Maps
• MapInfo®
Global Positioning System (GPS)
GPS devices receive global positioning information from government owned and operated satellites. Many
manufacturers have developed consumer grade GPS devices for the commercial market. In most
commercial applications, the GPS is used to approximate a location while in motion (such as boating,
hiking, or skiing). These devices are readily available to the consumers for a price of about $500.00 or
less.
As a note, the signal from the government satellites has intentionally
been degraded for security purposes. Commercial grade GPS
specifications are typically +/- 300 meters. Only industrial grade GPS
equipment, with a land based reference, will provide the type of
accuracy used in military applications.
When considering the use of a GPS for constructing and maintaining a UtiliNet network, here are some
issues to evaluate: