[R-sig-Geo] raster package and tiling schemes

[Michael Sumner]

On Fri, 22 Jan 2016 at 20:13 Tomislav Hengl <hengl at spatial-analyst.net>
wrote:

>
> If this can be of any help, I spend a lot of time tiling and working
> with large rasters in R (usually a combination of R, raster and sp
> packages + GDAL utils and SAGA GIS) so eventually I have made my own
> tiling functions:
>
> http://gsif.r-forge.r-project.org/tile.html
>
> The source code is at:
>
> https://github.com/cran/GSIF/blob/master/R/tile.R
>
> Here is an example of how to combine all these things to plot large
> rasters in parallel (still experimental, but you will get the idea):
>
> http://plotkml.r-forge.r-project.org/plotKML.GDALobj.html
> https://github.com/cran/plotKML/blob/master/R/plotKML.GDALobj.R



Great, that looks good Tom.

Cheers, Mike.



>
>
> T. (Tom) Hengl
> Researcher @ ISRIC - World Soil Information
> Team member Africa Soil Information Services http://africasoils.net
> Url: http://www.wageningenur.nl/en/Persons/dr.-T-Tom-Hengl.htm
> Network: http://profiles.google.com/tom.hengl
> Publications: http://scholar.google.com/citations?user=2oYU7S8AAAAJ
>
>
> On 21-1-2016 15:02, Michael Sumner wrote:
> > On Thu, 21 Jan 2016 at 04:00 Alex Mandel <tech_dev at wildintellect.com>
> wrote:
> >
> >> On 01/19/2016 09:22 PM, Michael Sumner wrote:
> >>> Hi there, does raster or any related package have any built-in  schemes
> >>> that allow for easy management of tiles?
> >>>
> >>> Raster itself provides a very powerful platform for building such a
> >> scheme,
> >>> since we can reasonably easily reclassify analogous RasterLayers at
> >>> different resolutions, and map cell values from one raster to another -
> >>> being careful with tile overlaps and alignment of course.
> >>>
> >>> Anyone working on such a thing already, or got any grand plans?
> >>>
> >>> I know rgdal and friends provide access to the GDAL tools in various
> >> ways,
> >>> but I want something in R only.
> >>>
> >>> Cheers, Mike
> >>>
> >>
> >> What's the goal of tiling? And when you say tiles do you mean multiple
> >> zoom levels like web tiles, or more a raster catalog like a VRT of
> >> multiple rasters next to each other?
> >>
> >> If you mean zoom levels, things like pyramids in tiffs are local
> >> equivalent but that's only for viewing data, not really useful for
> >> analysis.
> >>
> >> If you mean things that are adjacent to each other, I would assume that
> >> if they aren't all the same resolution/scale then you need to go to the
> >> lowest common denominator and resample everything to that to get a
> >> seamless data set. In this case the Raster merge and mosaic functions.
> >> Though if you want to keep the files in pieces, save them all out into
> >> the same resolution/scale, clipped to no longer have overlap, and
> >> gdal_buildvrt.
> >>
> >> Or am I missing the point?
> >>
> >>
> > Thanks Alex, these are good questions. I just want to be able to do it
> > arbitrarily for lots of reasons, but right now I want to tile up some
> > global data sets and allow my code to access them from a website at
> > different resolutions.
> >
> > Basic stuff. Stuff that should be basic and on hand. The machinery behind
> > raster::getData is probably a good place to start, to augment the SRTM
> with
> > non-land areas.
> >
> > I'll get to it, but keen to hear of alternatives. (It's kind of amazing
> > that there's still no comprehensive global source for
> bathymetry/topography
> > data as a service.)
> >
> > Cheers, Mike
> >
> >
> > -Alex
>
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-- 
Dr. Michael Sumner
Software and Database Engineer
Australian Antarctic Division
203 Channel Highway
Kingston Tasmania 7050 Australia

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