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FAQ: Difference between revisions
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=Selecting a Weather Station sensor site= | =Selecting a Weather Station sensor site= | ||
A simple guide is at [http://weatherfaqs.org.uk/node/124 uk.sci.weather newsgroup], note this advises against roof mounting. | |||
An attempt to compare the conflicting siting standards that apply across the world is included in a portable document format guide from [ftp://ftp.campbellsci.com/pub/outgoing/apnotes/siting.pdf Campbell Scientific]. | |||
For more advice see the website of your local Meteorological Bureau, an educational place (e.g. in USA see [http://newa.nysaes.cornell.edu/public/NEWAStationSitingGuidelines.htm Cornell University]), the [http://library.wmo.int/opac/index.php?lvl=notice_display&id=12407 World Meterological Organisation] (WMO), or a specialist organisation (e.g. in UK see [http://www.rmets.org/weather-and-climate/observing/guidelines-observing-0 Royal Meteorological Society] rather than the Met Office web site). | |||
Modern Stevenson Screens are uPVC constructed with a black interior (so they do not radiate heat onto the sensors) and a white exterior (so they reflect as much radiation as possible). There is a lot of discussion on the [http://sandaysoft.com/forum/viewforum.php?f=16 Homebuilt forum] about different approaches to improving measurements, and the problems with out of the box instrumentation from the different manufacturers. | |||
If you are contributing to an external site like APRS/CWOP, Weather Underground, PWS weather, Weatherbug and/or WOW, see guidance from these organisations re instrument placement. | |||
'''Note:''' Some stations have all sensors in one unit, positioning of these is a compromise between the ideals below for each sensor. | |||
== Where should I position the wind sensors == | == Where should I position the wind sensors == | ||
In the UK, the standard climatological measuring height is 10 metres. Advice varies on whether you should apply a correction factor for any lower height. Cumulus allows you to apply such a factor to either just wind speed, or wind speed and gust speed, by using the Calibration screen within the configuation menu. In the Cumulus Help it recommends that you also adjust wind chill - in practice this means ask Cumulus to ''calculate wind chill'' by selecting this in the settings frame on the '''station settings screen accessed from configuration menu''' (i.e. ignore any wind chill output by your weather station). | |||
If you are mounting near a building of height 'h' above ground level, ideally the wind sensor should be at a height of '1.5 times h' above ground level. | |||
If you are positioning away from a building or tree (or other object) of height 'h' (or the mean height of several objects is 'h'), then the distance away depends on which standard you are trying to meet, and can vary between 1.5 and 3 times 'h'. | If you are positioning away from a building or tree (or other object) of height 'h' (or the mean height of several objects is 'h'), then the distance away depends on which standard you are trying to meet, and can vary between 1.5 and 3 times 'h'. | ||
== Where should I position the rain sensor == | == Where should I position the rain sensor == | ||
The WMO says the rain gauge should at a distance away of 2 times the height of each nearby object (buildings, trees, walls, solid fences etc.) and just high enough off ground level to avoid possibility of splashing. You can experiment, but for amateurs, no more than a metre off the ground (or roof if mounted above it) and at least a metre from any chimney, wall or solid fence whose height exceeds that of the sensor seems good enough for most gauges. | |||
See [[Rain measurement]] or your local offical organisation. | See [[Rain measurement]] or your local offical organisation. | ||
== How do I protect my rain gauge against spiders or other natural problems == | |||
There is a lot of discussion on the [http://sandaysoft.com/forum/viewforum.php?f=16 Homebuilt forum]. In terms of siting, it is important to position your rain gauge where you can safely get to it. | |||
== How do I get good temperature and humidity measurements == | == How do I get good temperature and humidity measurements == | ||
The international standard states ambient air temperature/humidity is measured at 1.25 metres above ground level, above soil or grass not paving, protected from direct sun radiation (and direct rain), unless you are measuring soil or ground temperatures. The height is important for derived values as an air frost is defined as a temperature below the freezing point for water at this height, and the count of these is a standard reporting requirement in some countries. | |||
If you are using a ''Fine Offset sensor'', the thin depth of the thermonmeter/hygrometer (transmitter) should face where your console (receiver) is, for maximum transmission strength/distance, with the wide face at right angles to the transmission route. (Although if you use a model requiring a radio time signal, you will probably be trying to optimise that instead). | |||
== Pressure == | == Pressure == | ||
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== Solar == | == Solar == | ||
One would expect solar sensors should be positioned for maximum unshaded exposure to sunlight throughout the year, but again the forum contains advice for specific makes. | |||