[postgis-users] How to SELECT one day's scene (Landsat 8 scenes)

[Jackie Nguyen]

Hi Resmi-C,
We have a new cover each 16-day from Landsat 8. But I only want one cover
in result of my query. I had add new column 'date_of_data' to store date of
a raster. And I think range could solve my problem.
Thank you!


On Wed, Mar 19, 2014 at 4:16 PM, Rémi Cura <remi.cura at gmail.com> wrote:

> It is a little bit hard to understand what you mean..
> As a summary :
> _you have lot's of rasters.
> _Each one as a position (and a date associated?).
>
> You need to get a raster based on its position (where st_intersects(..))),
> but it is not sufficient and you would like too also filter by date.
>
> You can do so easily by adding a condition  in the WHERE, like
> AND my_date < .... AND my_date > ...
> (or using time_range
> http://www.postgresql.org/docs/9.2/static/rangetypes.html , if postgres
> version >= 9.2)
>
> Now about making a table per day, it is entirely another question.
> logically wise, you could get the strict equivalent by adding a column on
> your raster table with the day of acquisition (the real date would be
> better).
>
> Now deciding to split or not your big raster table into several smaller is
> more about performance, and should be carefully designed (
> http://www.postgresql.org/docs/9.3/static/ddl-partitioning.html), based
> on row number, index size, your memory size, how the table will grow, what
> kind of usage you make of it, and so on.
>
>
> Cheers,
> Rémi-C
>
>
>
> 2014-03-19 8:28 GMT+01:00 Jackie Nguyen <justaniceguy.nguyen at gmail.com>:
>
>> Hi PostGIS Users,
>>
>> I have a huge dataset of raster in PostGIS. Each scene is divided into
>> tiles (tile-size 500x500). I was trying to SELECT rast FROM landsat8
>> WHERE ST_Intersects(rast, polygon). It runs very slow, because it
>> returns longitudinal scenes of raster. Where I just want one day's scene.
>> But the problem is if I query with fixed date, adjacent scene with
>> different date won't be selected. That's not true.
>> So I think about some solutions:
>>
>>    - Because Landsat 8 re-visiting every 16 days, so I will insert every
>>    16 days into different table. So I can query from raster that cover all the
>>    earth without duplicate.
>>    - I'm not sure about ST_Within(), ST_DWithin() then SELECT rast that
>>    doesn't overlap other >50%
>>
>> What would you do in this situation?
>>
>> --
>> ----
>> Jackie
>>
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>
>
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-- 
----
Jackie
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