[SciPy-User] MODIS data and true-color plotting

Charles R Harris charlesr.harris@gmail....
Sun Nov 13 18:53:39 CST 2011


On Sun, Nov 13, 2011 at 5:39 PM, Charles R Harris <charlesr.harris@gmail.com
> wrote:

>
>
> On Sun, Nov 13, 2011 at 5:20 PM, Gökhan Sever <gokhansever@gmail.com>wrote:
>
>>
>>
>> On Sun, Nov 13, 2011 at 4:39 PM, Charles R Harris <
>> charlesr.harris@gmail.com> wrote:
>>
>>>
>>>> I'll take a look, I think I still have both the geolocation file and
>>> the data file somewhere, but they are rather large so it might be easier if
>>> you just download the files from the NASA sight once I can recall exactly
>>> where that was. You need both for the level 2 products in order to
>>> disentangle the overlapping push broom swaths and the viewing geometry and
>>> interpolate the result for the projection. It's a non trivial problem that
>>> I left to the swath tool. Some of the other tools are supposed to be able
>>> to do that also, but the documentation wasn't good enough that I wanted to
>>> pursue that line. Also, installing the swath tool on linux leaves some
>>> needed info in the .bash_profile file that you might want to move to
>>> .bashrc, I don't know how things work on windows. I think the higher level
>>> data products are easier to deal with.
>>>
>>> I wasn't overjoyed with the state of the NASA public software ;)
>>>
>>> Chuck
>>>
>>
>> Thanks. One thing that is still not clear in my mind is the use of ms2gt
>> or any other swath 2 grid converters (java tools for your example): are
>> these mandatory tools to handle MODIS data? I understand that ms2gt does
>> map projection specialized for MODIS data. So far so good. But what does it
>> mean to plot already projected data in Basemap? What is the solution to
>> this problem? Somehow the IDL True Color tutorial that I provided
>> originally gives me guidance to construct the RGB array, but from that
>> point onward I am not sure how to plot that data in basemap with/without
>> using ms2gt. Any pointers for this map plotting?
>>
>
> You need to use the same projection as basemap and I don't know what that
> is or what ancillary data is needed, matplotlib might be a better list for
> that. There are a ton of available projections in the swath tool, except
> the orthographic one that I wanted ;) The ms2gt tool is new to me, looks
> like it might be quite useful and easier to use than swath2grid.
>
>
I should mention that if you just plot the raw data you will see double in
spots. You need software that deals with the overlapping whisk broom swaths
and puts them on the map. There are many available projections for the
output of that process, so the final product isn't modis specific. There
are also file formats that are standard, geotiff for example, that other
software can use. So that might be a better output file type for you to use
than the h5 file format I was using. The GDAL software suite might have
something for that, it may even be possible to use it for the swath
conversion, but if so it is a secret known only to the developers ;)

Chuck
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