novel approaches to expression and detection of oestrus in dairy cows

depending on the technologies and algorithms employed, although it
cannot be used for positioning indoors or in obscured environments due to
poor satellite visibility and, hence, poor accuracy and reliability. GPS (the
Global Positioning System) is the main technology currently providing
absolute global positioning, within the above accuracies, although as with
all GNSS, GPS signal quality and reliability are severely degraded indoors
and in obstructed environments. Therefore although the principle is
established, this method is unsuitable for the purpose of oestrous
detection; cows are housed indoors and greater accuracy is required to
monitor precise cow interactions. A potential solution to the degraded
accuracy of GNSS is augmented GNSS to increase the integrity, reliability,
accuracy and continuity of position. Horizontal accuracy can be increased
from 10-12 metres to 1-2 metres, although this is not useful for the
purpose of oestrous detection, and indoor positioning is still a big challenge
even with augmented GNSS systems (Meng et al., 2007). High sensitivity
GNSS and assisted GPS enhance accuracy, however are still not capable of
precise positioning indoors (Meng et al., 2007).
There are location sensing technologies that aim to overcome the
limitations of the above systems and aim to address the issues of
ubiquitous positioning for use in obstructed environments; ground based
pseudolites, Ultra-wide band (UWB) and radio frequency identification
(RFID). Pseudolites can supplement GNSS by providing extra ranging
signals and improved transmitter geometry to enable precise positioning in
restricted areas with the possibility of use indoors. RFID can also be
combined with GNSS to provide precise positioning in areas that GNSS
cannot reach, although RFID only functions in 2D. Both methods are
limited in their accuracy and ability to provide indoor positioning, although
showing potential, they are in the early stages of development (Meng et
al., 2007). In contrast, UWB technology is capable of monitoring location in
3 dimensions in indoor environments. One UWB system, developed by
Thales Research UK (TRT), has reported accuracy calculated to ‘a fraction
of a metre’ in a range of indoor and harsh environments in all 3
dimensions, for example achieving 30cm accuracy in the most difficult
dimension of height (Ingram, 2006). UWB also has proven use in harsh
environments; monitoring emergency personnel for example in burning
buildings, forest fires or during natural disasters (Ingram et al.,
2004;Ingram, 2006;Harmer et al., 2008;Dona et al., 2009).
82