Specifications

9
Fig. 2.1: Two common approches to extract soil moisture from ET (figure proccured from
Bernard et al. [1]).
still refl ects 6% error [4]. The model inaccuracies coupled with the lag and interval delays
introduce too much error for some to grow crops or to report solid scientific numbers using
these methods. However, Verhoest et al. [4] claims that more ground data is needed to
continue refining their subsurface property estimation models.
2.2 Current Methods of Environmental Property Determination
The basic building block to any ground system designed for data acquisition is the single
site measurement and control device commonly termed in the literature as a “datalogger.”
The term datalogger refers to many device classes from weather station controllers to a
freezer temperature recorder. Some of their features include but are not limited to analog
and digital measurement capabilities, onboard data storage, and basic RS-232 or advanced
commu nications links like the GOES satellite data-link. Dataloggers form the backbone of
most weather stations and can be interfaced with sensors to measure the subsurface proper-
ties directly [10,11]. For a small scale network of loggers (e.g., less than 20 devices), wired
systems us ing RS485 or 900MHz point-to-multipoint radio connections are most common.
Many of these systems can be found at USU and other universities. In particular, Greenville