Re: Gridded depth data

Hi Ian,
On Wednesday, May 15, 2002, at 04:26 PM, ian mayo wrote:

> Hi all,
> I'm currently sub-classing the OpenMap VPF layers to provide coastline
> and
> depth contours in the Debrief maritime analysis application at:
> http://www.debrief.info
>
> My users would like a more detailed dataset, particularly in shallow
> waters
> (as is provided with a gridded dataset).
>
> I have found, and experimented with the ETOPO layer, which gives great
> results (particularly after I switched from the slope-algorithm to just
> plotting colour-coded depths).
>
> Unfortunately, the users would now like higher resolution gridded depth
> data.
>
> So, here are my questions:
>
> - 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?

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.

> - 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.

> - 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.

Regards,

Don

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Don Dietrick, BBN Technologies, dietrick@bbn.com
10 Moulton Street, Cambridge, MA 02138
617-873-3031 [fax]-2794
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