surface Datum Pressure Barometric and Surface Datum Elevation above See Level

[xiao]

Hi!

i am in the phase of defining the enviroment Setting using existing measurments and came across of this question:

it seems that Ventsim defined a relation between the Surface Datum Pressure Barometric and the Surface Datum Elevation above Sea Level?

We have measured the Barometric Pressure of 100,58 kPa at a hight of  +133,8 Meter. But every time when i change the Pressure to 100,58 kPa the elevation will be ajusted to 62,2 m, which is not correct. (with messured Dry Bulb and Wet Bulb temperature filled in)

How can i fix this Problem?

Thanks in advance.

 

Xiao Yang

 

Edited May 18, 2022 by xiao

[Martin Griffith]

Hi Xiao, 

Thanks for your message. 

The surface elevation above sealevel and the reference barometric pressure are linked, so if you change one, then the other will update. This is hard-coded in Ventsim to represent standard relation between air pressure and elevation. But this can vary locally (and seasonally) as it seems to at your site.

The barometric pressure is the important one. I would advise that you set the correct barometric pressure and then ignore the elevation above sealevel. The elevation above sealevel is only used as a reference in the settings, as a way to calculate the barometric pressure and to calculate the airway elevation above sealevel on the Info tab of the Edit Box. 

So for this problem, set the barometric pressure and ignore the resulting elevation above sealevel. And we will have a think about how to better handle this in the settings. 

 

[Martin Griffith]

What is important is that the Surface Datum of MineGrid setting corresponds to the Z coordinate in your model at which the surface barometric pressure was measured. 

To check this, after you have set up your Heat Simulation, if you check the Barometric Pressure in your model at the elevation you entered for Surface Datum of Minegrid, you should get the Surface Barometric Pressure. Example below: