[postgis-users] Simple Line Density

[Karl Zinglersen]

A very good idea, I've forgot it in this installation. Thanks

Karl

Den onsdag den 27. november 2013 13.49.08 UTC-3 skrev Rémi Cura:
>
> Maybe you should tweak your postgres conf file ,
> default conf is very savy
> http://www.postgresql.org/docs/9.3/static/runtime-config.html
>
> Cheers,
> Rémi-C
>
>
>
>
> 2013/11/27 Karl Zinglersen <karl.zi... at gmail.com <javascript:>>
>
>> Hi,
>> I am dealing with the same types of data and issues as Jeff.
>> My procedure for data clean up is: 
>> 1) CSV files into PostGIS as points
>> 1.1) ST_TRANSFORM to projected spatial reference (here EPSG:32621 / UTM 
>> zone 21 N WGS84)
>> 2) ST_MAKELINE to "sub"-lines via PARTITION BY
>> 3) Create a gridded polygon layer in same srid
>> 4) Run equivalent to select cell_id, line_id from cells, lines where 
>> intersects(lines.geom, cells.geom 
>> - but my postgis runs out of memory after a while. And I am sorry to say 
>> Spatial Analyst doesn't.
>> Is there more memory cheap way to do it in PostGIS (e.g. via the raster 
>> functions - although I haven't found i yet).
>>
>> Karl
>>
>> Den onsdag den 26. december 2012 09.58.43 UTC-3 skrev Jeff Adams - NOAA 
>> Affiliate:
>>>
>>> Hi Brent,
>>>
>>> Thanks for the response. I don't think your original response made it 
>>> into my inbox via the list, but now I see it on the website thread. That 
>>> seems like it might be a viable alternative, I just worry about those 
>>> vessel tracks that would be clearly outside of a particular grid cell, but 
>>> whose buffer would bleed over. How did you handle this type of situation?
>>>
>>> Jeff
>>>
>>> On Mon, Dec 24, 2012 at 7:22 PM, <pcr... at pcreso.com> wrote:
>>>
>>>> Jeff,
>>>>
>>>> Did you see my reply using vessel tracklines as vectors & a grid in 
>>>> Postgis to do exactly what you describe?
>>>>
>>>> Given we were looking at benthic impact, we buffered the tracklines to 
>>>> create polygons representing the swept area of the deployed fishing gear. 
>>>> These were clipped by the cells, & we could generate statistics suca as the 
>>>> cumulative swept area of all tracks with each cell, number of times each 
>>>> cell was crossed, & given the tracklines have a timestamp associated with 
>>>> them, we could also look at the temporal pattern of tracks crossing cells, 
>>>> for things like seasonal impacts & variation between seasons. 
>>>>
>>>> Cheers,
>>>>
>>>>   Brent Wood
>>>>
>>>
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