[mapserver-dev] Call for vote on RFC 78

[Daniel Morissette]

Yup. I confirm that as Steve pointed out, a VRT would be the way to go 
in this case.


On 11-11-17 05:35 PM, Brent Fraser wrote:
> 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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>
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-- 
Daniel Morissette
http://www.mapgears.com/
Provider of Professional MapServer Support since 2000