[postgis-users] Simple Line Density

[Karl Zinglersen]

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 <javascript:>> 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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