Re: Gridded depth data

Hi Don,

> >
> > - Can anybody advise me on the algorithm for producing new ETOPO
> > datasets in a format suitable for OpenMap? I've found where to
> > download them, but am unsure about how to put them into the OpenMap
> > format.
>
> So you have ETOPO files in higher resolution than 5 minutes, or you've
> found barythmic elevation data?
>

Yes, I've found higher resolution ETOPO data, at a 2 minute resolution.

> The ETOPOLayer can handle 5 minute resolution data, I think you just
> need to put those data files in the etopo directory. If you have higher
> resolution data, then some minor adjustement to the code may be
> necessary to read them.

I need to find the correct format to store them in. The files are
downloadable in a number of resolutions, but inspecting the OpenMap code
suggests that it's reading in the data-files as Java binary data. I also
need to know how the elevations are ordered in the file.

>
> > - Can anybody advice me on any other OpenMap data formats which would
> > display gridded depth data?
>
> Once you have the elevation data, you can use the OMGrid object to
> display it. You just need to use/create an OMGridGenerator to let the
> OMGrid object know how to display the data.
>

I believe I can get hold of DBDB-V gridded depths, which I believe come as
several directories of data organised spatially. I was quietly hoping there
would be an OpenMap library capable of extracting this data to form a layer.

> > - Has anybody else noticed that the 5 minute ETOPO data available as
> > part of the ETOPO download with OpenMap has the data at zero
> > degrees longitude missing? If you switch off the graticule in the
> > OpenMap
> > viewer you will see the black line where the data is missing.
>
> Hey lookit that! That's not a bug, it's a feature.
>
> I'm not sure if that means data is missing, or if it has something to do
> with +- 0. Probably the latter, since in greyscale mode the line is
> just plain grey.
>

Looking in the datafile shows that at all latitudes the value is zero. I
presume it should take a value.

> Regards,
>
> Don
>
>

Thanks for your support so far Don,
Ian

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