Importing DCP dataset

[thopri]

Hi,

I am trying to import a DCP dataset into vapor but am getting an error message as follows

The ncdump of the dataset is as follows.

netcdf particles_dcp_static {
dimensions:
        P = 8640 ;
        T = 1 ;
variables:
        double T(T) ;
                T:units = "seconds" ;
        float Position_x(T, P) ;
                Position_x:units = "degrees_east" ;
        float Position_y(T, P) ;
                Position_y:units = "degrees_north" ;
        float Position_z(T, P) ;
                Position_z:units = "meter" ;
        float temperature(T, P) ;
                temperature:units = "Celsius" ;

// global attributes:
                :Conventions = "CF-1.8" ;
                :title = "Non-time-varying Particle Data" ;
                :institution = "Example Institution" ;
                :source = "Synthetic data for demonstration" ;
}

I can import (in an empty session) when the x y z variables are in one “axis” dimension but I then have issues with x/y being in decimal degrees and z being in meters. z is stretched far out (or x/y are really compressed) as vapor assumes the units are the same.

As an aside, I am also trying to add this dataset to an already imported netcdf-cf dataset (GEBCO bathymetry). As part of opening the bathy vapor seems to convert the lat and long values to metres. I cannot get this to happen to the particle netcdf. I am hoping that the units being applied will correct this.

I have also tried importing without a time dimension and also with a single timestep of 0 seconds (which you see here) this has had no effect.

[pearse]

Hi, and sorry for not responding sooner. Our team talked about this and we came to the conclusion that it would be a pretty large effort to support units in the DCP reader. Currently, the best path forward would be to modify your coordinate data from lat/lon to meters from the equator/prime-meridian intersection.

Let me know if you need any help. We’ve noted unit support as a potential feature.

-Scott

[thopri]

Hi,

Thanks for the clarification I have converted the decimal degrees into metres and the particle dataset now plots as I would expect. My next problem is that I want to overlay it with a bathymetry dataset. This imports and opens in Vapor fine but as part of that process, vapor generates a latx and lony coordinates which are metres. I initally thought they would be referenced to the equator and prime meridian as you mentioned but the screenshot below shows that not to be the case.

It seems that is uses the centre of the dataset as an origin point? I guess I can convert these into the same metre units as my particles but was hoping I wouldn’t have to do that?

[pearse]

Thanks for the clarification I have converted the decimal degrees into metres and the particle dataset now plots as I would expect.

Great, glad to hear it!

This imports and opens in Vapor fine but as part of that process, vapor generates a latx and lony coordinates which are metres. I initally thought they would be referenced to the equator and prime meridian as you mentioned but the screenshot below shows that not to be the case.

Sorry about this, I was wrong and this can vary depending on the projection of your dataset. For mercator, the origin does reside at the Null Island intersection point but this is not always the case.

It seems that is uses the centre of the dataset as an origin point? I guess I can convert these into the same metre units as my particles but was hoping I wouldn’t have to do that?

That’s one approach. If the bathymetry and particles are not too misaligned, you could also translate one of them to match the other. This can be done in the Geometry tab of a given renderer (screenshot below).