Kipp&Zonen BSRN Scientific Solar Monitoring System - Manual (Page 36)

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data. W hile it is im possible to have com plete defence against loss, the need
for security m ust be balanced against the cost of its im plem entation.
Distance: The physical distance between the data collection location and the data
archive location will often determ ine the m ethods of com m unication that are
available. For exam ple, the only viable solutions for long distances m ay be
com m on carriers or even satellite com m unications, while shorter distances
(e.g., within a com plex of buildings) can utilize hardwired local area
networks.
Environm ent: Physical or legal constraints m ay affect the type of m edium that can be
used. Local ordinances m ay prohibit the use of certain types of radio
com m unications or the laying or stringing of cable. C lim atic variables, such
as wind, tem perature, rain and icing conditions also need to be considered
when selecting a com m unication m edium . For exam ple, overhead wires in
areas where icing is a com m on problem m ay not provide a reliable m eans of
com m unication.
Application: Peculiarities in particular applications will dictate significant portions of the
selection of a m edia. This is especially true at rem ote sites where power
conservation requires only lim ited com m unication access. The slowest
portion of the com m unication chain will also dictate the overall requirem ents
of the entire chain. For exam ple, if com m unication between a data logger
and a com puter, through com m on carrier lines, is constrained by the baud
rate at which the data logger can transfer the data to the m odem , there is no
reason to purchase m odem s with a higher baud rate.
Maintenance: All m edia are subject to failure. The system design should take into account
the probability of a failure, the cost of such a failure to the user in m oney and
inconvenience, and the ability of the user to obtain alternate com m unication
m edia for the duration of the failure. Routine m aintenance m ust also be
considered in term s of down tim e and overall cost of the system .
3.4.4 Security
Depending upon the location, security m ay be a significant consideration. Security is both for the
protection of the site against vandalism and theft, and for the protection against harm of would-be
intruders (the concept of being responsible for a thief’s well-being while on the victim ’s prop erty
m ay well be found only in North Am erica).
At a m inium the m easurem ent site should be well-fenced against intruders, both hum an and
anim al. Further security m easures m ay include alarm system s, security lights (on buildings, but
away from the instrum entation) and video cam era system s.
In som e locales special security should be considered against burrowing and gnawing rodents.
3.5 Site Preparation
The preparation of the site before m easurem ents begin consists of designing the installation to
reduce interference of the sensors from buildings and other sensors, ensuring that the instrum ent
platform s are appropriate for the clim ate and soil conditions, and designing a signal cable grid that
is efficient and easy to m aintain. W hile general principles can be applied to each of these aspects
of the site, individual stations will require special adaptations to the following procedures.
3.5.1 Instrum ent siting
Care m ust be taken so that the instrum ents do not interfere with each other. Ideally, instrum ents
should be far enough apart that they becom e insignificant objects in the field of view of adjacent
instrum ents. Space lim itations, however, often restrict the distance apart instrum ents can be
placed. To reduce such interference, the instrum ents should be lined up in a poleward direction
with slightly increasing elevation. In cases where the m easurem ent of diffuse radiation and direct