[mapserver-dev] Call for vote on RFC 78

[Brent Fraser]

Steve,

   Thanks for the tip!  I think that would do the trick...

Best Regards,
Brent Fraser


On 11/17/2011 11:36 AM, Stephen Woodbridge wrote:
> Brent,
>
> I think you can create a gdal VRT thingy that allows GDAL to present 
> the two files as a single dual band image. This would keep the code 
> simpler in mapserver.
>
> Maybe Daniel or Frank can verify this assumption.
>
> Thanks,
>   -Steve W
>
> On 11/17/2011 10:21 AM, Brent Fraser wrote:
>> Daniel,
>>
>> Makes sense. As Steve W. points out, it could be done on angles by
>> averaging the components so you may want to at least keep it in mind for
>> a future enhancement when doing the implementation.
>>
>> Looking at the FTP site I listed, I see that the U/V components are
>> available for wind, but in separate files: nww3.UGRD.grb, nww3.VGRD.grb
>> (with 61 bands per file, one band per 3 hr forecast) . Would it be
>> possible to adjust the DATA object to allow for such a situation?
>> Something like:
>>
>> DATA nww3.UGRD.grb:1, nww3.VGRD.grb:1
>>
>> with the ":1" indicating the band to use.
>>
>> Best Regards,
>> Brent Fraser
>>
>>
>> On 11/16/2011 10:43 PM, Daniel Morissette wrote:
>>> On 11-11-16 11:58 PM, Brent Fraser wrote:
>>>> Alan,
>>>>
>>>> Any plans to allow for raster files containing direction values
>>>> (http://polar.ncep.noaa.gov/waves_old/products.html#grib, esp Mean 
>>>> Wave
>>>> Dir) instead of calculating it from components? Note: sample data
>>>> available at ftp://polar.ncep.noaa.gov/pub/waves, e.g. nww3.WVDIR.grb
>>>> (wave direction)
>>>>
>>>
>>> Brent,
>>>
>>> The approach of using u and v bands allows for resampling, which is
>>> essential to the approach of rendering vector fields at various
>>> scales, and I don't think is possible with a raster of direction
>>> (angle) values.
>>>
>>> i.e. as you zoom in and out, with u and v raster bands, you can
>>> average the u and v pixel values independently over an area and the
>>> average u and average v give you an accurate average vector for the
>>> area. However, I could be wrong, but I don't think you can resample
>>> and average the direction (angle) values over a block of pixels to get
>>> the same result.
>>>
>>> It's late here, so maybe you can prove me wrong.
>>>
>>
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>
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