[R-sig-Geo] best practice for reading large shapefiles?

Vinh Nguyen vinhdizzo at gmail.com
Tue Apr 26 22:33:35 CEST 2016

On Tue, Apr 26, 2016 at 1:12 PM, Roger Bivand <Roger.Bivand at nhh.no> wrote:
> On Tue, 26 Apr 2016, Vinh Nguyen wrote:
>> Would loading the shapefile into postgresql first and then use readOGR
>> to read from postgres be a recommended approach?  That is, would the
>> bottleneck still occur?  Thank you.
> Most likely, as both use the respective OGR drivers. With data this size,
> you'll need a competent platform (probably Linux, say 128GB RAM) as
> everything is in memory. I find it hard to grasp what the point of doing
> this might be - visualization won't work as none of the considerable detail
> certainly in these files will be visible. Can you put the lot into an SQLite
> file and access the attributes as SQL queries? I don't see the analysis or
> statistics here.

- I can't tell from your response whether you are recommending PostGIS
is a recommended approach or not.  Could you clarify?

- I am working on a Windows server with 64gb ram, so not too weak,
especially for some files that are a few gb in size.  Again, not sure
if the job just halted or it's still running, but just rather slow.
I've killed it for now as the memory usage still has not grown after a
few hours.

- Yes, the shapes are quite granular and many in quantity.  The use
case was not to visualize them all at once.  Wanted a master file so
that when I get a data set of interest, I could intersect the two and
then subset the areas of interest (eg, within a state or county).
Then visualize/analyze from there.  The master shapefile was meant to
make it easy (reading in one file) as opposed to deciding which
shapefile to read in depending on the project.

- I just looked back at the 30 PLSS zip files, and they provide shapes
for 3 levels of granularity.  I went with the smallest.  I just
realized that the mid-size one would be sufficient for now, which
results in dbf=138mb and shp=501mb.  Attempting to read this in now (~
30 minutes), which I assume will read in fine after some time.  Will
respond to this thread if this is not the case.

Thanks for responding Roger.

-- Vinh

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