wind direction from VP2

[Franklin]

I have used WsWin for some years now, until recently with a Huger weather station. But now I have changed to a Davis VP2, with Weather Envoy and USB data logger.

Everything works fine, and WsWin does its job as well as before. But I have noticed a strange thing in the format of the wind direction.

When my computer is on, and WsWin is running and downloading from the wireless inbterface every minute, the wind direction is registered in degrees and with a resolution of one degree.
But after a break (when computer or WsWin have been closed for some time) WsWin downloads the data from the datalogger and all wind directions registered at that time (i.e. for the duration of the break) are displayed with a resolution of 22.5 degrees 9in 16 directions) only.

This looks very strange in my graphs...

Is there a way to have the datalogger archive the direction in degrees too, rather than in 16 values only?

Thanks for your help, and gtx from Utrecht - Holland

[chris]

Hi Franklin,

I´m afraid the DAVIS datalogger only archives wind direction in 22.5 degrees resolution. You won´t find a 1 degree resolution in the WeatherLink database files either.

I think the logger memory only uses 1 digit in HEX format for storing wind direction, DAVIS obviously wants to save memory

Regards,
Christian

[Franklin]

Thanks for your quick answer, Christian. I was already afraid that it might be something like that... the alternative would be to have WsWin also graph with 22.5 degree intervals during the real time downloads....

I must try and see to find something to do that!

Gtx, Franklin

[chris]

Hi Franklin,

you might consider using the file watching mode. Assuming an archive interval of 1 minute every minute WsWin imports data from Weatherlink (just as it does when you start the program and it imports all missing data from the logger) so it is almost real time on your screen (in fact, the values are about 1 minute old). In this case wind direction ist imported from the logger in 22.5 degrees resolution.

There are also small differences in the average wind speed values (in real time mode the average ist calculated "in running" and exact to a tenth of kph whereas in file watching mode the value is imported from the logger where it is rounded to whole numbers in mph - the memory saving issue again! - so you only will find values of 1.6kph, 3.2, 4.8 and so on)

Regards,
Christian

[Franklin]

Thanks for your explanation, Christian.

I have been using file watching when I started using my VP2. But the Weatherlink program was very costly in terms of computing time and processor load! It did slow down other tasks I am using the machine for...

Another disadvantage was that I couldn't use the display, mini-display and instrument windows (or the display bar) to show the real time values.

I think that I can live with it as it is. After all I do need those real time values only when my computer is connected to the data logger - not after a pause when I have been out of the house. The graphs and tables show a little weird, that's all...

Gtx from Holland, Franklin.

[Franklin]

Hallo again, Christian (and others!)

I have looked more closely to how the wind data behave themselves.
You are right that the speed data are written in the data logger in multiples of 1 mph (or 1.6 km/h), just like the direction is done in 22.5 deg increments.

But the WsWin presentation in display / display / min-max bars is different for both parameters.

When in recording mode the wind direction is written into the display bar in the high 1 degree resolution indeed, but the wind speed is written there in the low 1 mph resolution. The latter would not be expected... unless VP2 has no higher resolution speed data at all.

In the graphs and in the one-minute readings which show in my min-max bar the speed is calculated with higher resolution. Awkwardly the direction (when written beside the speed) is in compass rose notation there (i.e. in lower resolution).

It seems that WsWin in recording mode takes real time VP2 values for direction, but data logger values for speed (or as stated above, perhaps VP2 has no higher resolution for real time for wind speed than the data logger values).
I suspect the latter being true, but in that case I wonder how WsWin calculates the speed value showing in the bottom line of the min-max bar.... perhaps from calculated wind run data during the one minute recording interval? It seems not very consistent, for in that case the graphs could be in higher resolution too...

It is very difficult to find out where all data presented in WsWin actually come from, and why a specific resolution has been chosen.

Another example: the air pressure is shown in tenths of a hPa in the display bar, but in the (mini)display the decimal fractions have disappeared.... why?

All comments welcome, of course.

Gtx from a blazing hot Utrecht - NL (31.3 deg C at 12:30 MEST)

[chris]

Hi Franklin,

the VP2 wind speed resolution is only 1 mph indeed (and I am not very happy with it either, the console only shows values of 2,3,5,6,8,10 etc. kph
due to rounding), but in recording mode WsWin calculates the 1-minute average by using all 23 or 24 wind samples per minute that are sent from the station. In file watching mode WsWin displays the value from the logger which is - due to saving of memory - rounded to 1 mph.

Regarding the barometric pressure in the (mini)display it seems there is no way of showing tenths - maybe Werner can correct me and point me in the right direction.

Greetings from Northern Austria (800m above sea level - therefore
quite pleasant: 27,3°C at 12 UTC)
Christian

[Werner]

@Franklin,

WsWin shows what available.
At barometric pressure in minidisplay it show value to 999.9 with decimals signs from 1000 hPa only without that.
Why? There is no place.

You will remark the same in the diagram - for example at rain ...

Werner