A little clarification on the use of the special observation 'wind' may be warranted.
As per the Wind section <http://weewx.com/docs/customizing.htm#Wind> in the Customization Guide WeeWX stores wind data in two distanct forms. Firstly windSpeed, windDir, windGust and windGustDir are stored as scalar values in the archive (provided your station emits them) just as any other observation. There are also corresponding daily summary tables that are used as an optimisation for long period stats such as $month, $year or $alltime if implemented. Again these function as per any other observation. Wind data is also stored in vector form but only in the 'wind' daily summary (ie not in the archive). This allows stats such 'what was the direction of the highest speed wind observed today' or this week, or month or year etc using a single tag. If this special vector form was not used then when you use something like $month.windDir.max (or $month.windGustDir.max) you will likely get 359 or 360 degrees, certainly not the direction of the wind during the 50km/hr gust that occurred yesterday. The upshot of this is that the special observation wind can only be used with the daily summaries. Many are not aware, but the daily summaries can only return data for a midnight-to-midnight, first ever record-to-midnight, midnight-to-last record or first record-to-last record periods. That is the daily summaries only store data as a summary for the day, they can't use part days unless it is the first day or last day of data stored in the database. $month.xxx, $year.xxx almost always use a midnight-to-mdnight boundary or first record or last record boundary. However, other tags such as $span and $trend aggregate over a period that does not fall on the boundaries supported by the daily summaries (well a $span over a delta that is a multiple of 24 hours would at midnight each day but that is not really usable) and in such cases the archive is used. But we don't have the special observation wind in the archive so hence $span($year_delta=5).wind.max will fail everytime except at midnight. So that is why $span.wind fails but $year.wind does not. Likewise as outTemp exists in the archive and the daily summaries, when you try to obtain an outTemp aggregate that does not sit on the boundaries supported by the daily summaries, WeeWX automatically drops back to the archive because outTemp is in the archive (try doing a $span on outTemp over a very long period that is not on a midnight boundary - the query will take some time as the archive is being used not the daily summary). The solution to the $span.wind issue is to use windSpeed, windDir etc or use $alltime. This means that it is not possible to display 'the direction of the highest wind speed seen in the last 36 hours' using a single tag, it will require some messy querying of the archive to find the highest wind speed seen in the last 36 hours and then finding the corresponding wind direction (again from the archive) at that time. Easily doable in a search list extension and could probably be done with some in-line template code but likely more than would be expected of a novice. Hope this goes some way to explaining why things did not work as expected. Gary -- You received this message because you are subscribed to the Google Groups "weewx-user" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
