[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[IDV #EWA-848337]: Method to convert Pressure field to Height Field

> >
> R/Sir
> Thanks a lot again.
> I am afraid, new Unit() may not be applicable for converting pressure to
> altitude. I think we need to go through some coordinate system conversion.
> The one I chose was Standard Atmospheric Coordinate System.
> Well frankly speaking, this is not my original idea. I was just going
> through getInitialSpatialDomain(GeoGrid geogrid) method in
> ucar.unidata.data.grid.GeoGridAdapter class. And I found that this is
> one way to convert pressure to altitude. Am I going wrong somewhere?
> Is this not the right way to convert Pa/hPa or millibar to meters. I
> know little about science. Please correct me if I am wrong. Actually I
> was just thinking that if you had such similar stuff in derived.xml,
> that could be utilized for converting pressure to height.

      I am still not quite sure if going through the coordinate conversion is 
the smart way to do it. There is a formula can be used to define the relation 
between pressure and altitude in the following URL:


This maybe better.

> I will describe you in detail why I need all this stuff. Actually we
> have our wind vector data product in HDF5 as Point Data (Compound Datasets).
> I mean
> Lat/Lon/UComp/VComp/WindSpeed/WindDirection/Pressure
> I created a datasource class that extends PointDataSource and does
> barnes analysis. And generates almost everything as expected.
> In between one query related to this, I was just going through
> ucar.unidata.data.point.PointDataSource class. Why the
> makeDerivedDataChoices method has been over-ridden like this:
> protected void makeDerivedDataChoices(List dataChoices) {}
> Any special reason?

I don't know, I need to check the source code when I back to office after new 
> I just over-ridded this method to generate Wind Vectors (using UComp and
> VComp) by using derived.xml. And I came to know about a few more
> meteorology specific stuff: vorticity, advection, etc.
> Now I was just trying to do some thing like Wind Vectors draped over
> topography. The topography I was trying to generate was by using
> pressure values. That is why I had to write the createHeightField()
> method taking pressure field as input.

> And one more display control, I am planning to build up is 'Wind Vector
> shaded by another parameter'. This another parameter I am planning to
> use is Pressure. The reason is the  scientists dealing with winds here
> use such displays for their analysis.

You can use the formula "Formula > Grids > One value colored by another" to do 

> I am cc'ing this mail to Don Sir too in case he has something to say.
> I am bad in communicating at times. Please do revert back if I am
> ambiguous somewhere.
> regards
> Ghansham

Ticket Details
Ticket ID: EWA-848337
Department: Support IDV
Priority: Normal
Status: Open

NOTE: All email exchanges with Unidata User Support are recorded in the Unidata inquiry tracking system and then made publicly available through the web. If you do not want to have your interactions made available in this way, you must let us know in each email you send to us.