Specifications

10
farm, located in Logan, Utah, has a system that falls under this category that uses point-
to-multipoint radios to tie six weather stations together [12]. T.W Daniel’s Research Forest
site, situated in the mountains above Bear Lake, Utah, interconnects sixteen dataloggers
using RS485 [13].
On a large scale, systems are connected u sing TCP/IP, satellite telemetry, or long
distance data radios. The Intern et provides the ability to connect sites from many different
places around the world. Any system d esiring to use this link needs only conform to
the TCP/IP specification and operate as a web-application or web-database. Campbell
Scientific Incorporated sells the NL100 Ethernet Adapter to enable their products to be
accessed using a TCP/IP network or Internet [14]. In more remote areas of the globe
where the Intern et is not accessible, satellite telemetry (e.g., Iridium, GOES, etc.) is used.
One use for Iridium satellites are Dart-II buoys for oceanic weather and tsunami warning
systems [15]. The Snotel system used by the NRCS uses Meteor-Burst radios that use VHF
band radio waves that bounce waves off of the Ionosphere. This technology is capable of
transmitting over 1,000 km [16]. As of June 2003, over 660 Snotel sites were in operation
[11]. Or ganizations like the National Oceanic and Atmospheric Administration (NOAA)
collect environmental data from various sour ces using all of the above mentioned means.
NOAA supplies meteorologists and scientists with current weather data through a web
database [17].
2.3 The ZigBee Protocol
The metho ds mentioned above are sufficient to satisfy the need for spatially variant data
in the presence of external infrastructure. However, in rural areas the current technologies
support localized wired networks or wireless networks with topologies more suited for devices
ten miles or more apart [18]. ZigBee, a derivative of IEEE 802.15.4, is a wireless protocol
that focuses on highly reliable mesh networks optimized for low data rates an d a device
grid-size of less than a mile. The protocol was first established in 2001 [19]. In 2006, the
first commercail ZigBee compliant radio modules were released. Moving towards 2008, these
modules are becoming a popular interface for remote sensors [18].