Luminosity or Illuminance?

[Steeple Ian]

In the current WeeWX repository.

I am looking at wview_extended.py in the /scr/schemas folder. On line 77: -

('luminosity' ,     'REAL'),

Am I correct in thinking that this may be incorrect and should actually be 'illuminance'?

Thanks,

Ian

[vince]

Perhaps. It's interesting that the weewx docs have an example of renaming 'luminosity' to 'illuminance' (link) and mention if for one model of fousb only.

• https://en.wikipedia.org/wiki/Luminosity - energy per unit of time (W)
• https://en.wikipedia.org/wiki/Solar_irradiance  - energy per unit of area (W/m2)
• https://en.wikipedia.org/wiki/Illuminance (aka brightness) in lux - https://en.wikipedia.org/wiki/Lux

FWIW as an example - a WeatherFlow station emits 'solar_radiation' and 'illuminance' readings from the hardware. They report them as W/m2 and lux respectively.  Weewx group_radiation uses W/m2 for 'radiation' and 'maxSolarRad' and group_illuminance uses lux for 'illuminance' if that helps any.

There was a long discussion in jan-2019 (wow) in the WF dev forum about the differences.  That particular gear derives radiation from the brightness and uv sensors in the hardware.  Guess every vendor does it their own way.

I think you talked my 'perhaps' above into a 'probably yes'.

[gjr80]

The illuminance/luminosity issue has come up several times over the past 4-5 years. I'm aware of issues #613 and #685 and this weewx-user thread, there may well be others. From memory, I recall the following from a chat that Tom and I had some years ago:

- we agreed that the wview_extended field luminosity should be re-named or a new field added and whatever fields we end up with should be assigned a WeeWX unit group by default

- we could not come up with a solution that would not impact existing users that utilise a 'light' related field (I do not include 'radiation' or 'maxSolarRad' to be a 'light' related field)

- we agreed to leave things as they are until a solution was developed

Unfortunately the record of that chat has long disappeared into the ether.

At present the wview_extended schema includes a field named 'luminosity' but no field 'illuminance'. WeeWX assigns the field 'illuminance' to the unit group 'group_illuminance' (which only supports the unit Lux), WeeWX does not (by default) assign the field 'luminosity' to any unit group. This disconnect/omission provides a degree of protection in preventing illuminance data being unwittingly stored in the luminosity field as any such arrangement would require the user to make deliberate schema/unit group assignment/field mapping changes.

Not a solution but a little history as to why we find ourselves in the position we are now.

Gary

[steepleian]

Thanks Gary and Vince for your feedback. I did actually find some strands of your conversations which piqued my interest. I kind of thought there might have been an unresolved dilemma in there somewhere and now you have confirmed that. It’s given me some food for thought.

Thank you

Ian

https://claydonsweather.org.uk

On 23 Nov 2024, at 02:00, gjr80 <gjrod...@gmail.com> wrote:

The illuminance/luminosity issue has come up several times over the past 4-5 years. I'm aware of issues #613 and #685 and this weewx-user thread, there may well be others. From memory, I recall the following from a chat that Tom and I had some years ago:

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