[gdal-dev] help using gdal_grid ...

[Andrey Kiselev]

On Thu, Jun 05, 2008 at 09:09:29AM -0400, Paul Spencer wrote:
> Ok, so that's what I tried with about 1.8 million points (I miscounted
> originally) and I never actually succeeded in producing a DEM.  GRASS
> was able to suck in the points and produce a smoothed DEM in about 4
> hours on my mac including my learning curve having never actually used
> GRASS.  It is entirely possible that my scripts are inefficient etc
> but it seems to me that gdal_grid is not really suitable for
> processing large amounts of elevation data at this point in time.
> 
> With all due respect to the developers, I would suggest that the web
> page for gdal_grid give a bit more detail about the potential
> performance problems and some strategies for optimizing gdal_grid.
> 
> It might also be a reasonable enhancement to introduce a mechanism for
> windowing the input data into small buckets based on some grid size -
> for instance, it might be very reasonable to have a 10x10 window and
> pre-process the input points into each spatial area then run the
> analysis on the 10x10 window using the points from that window plus
> the surrounding 8 windows (for instance).  I think this approach would
> (in at least my case) have produced much faster results with no
> difference in the resulting output.

Hi Paul,

The actual problem is that I haven't tried to optimize gdal_grid at all
yet. My purpose on this stage is to get correct results and start
thinking about optimization later (it can be quite a long term, because
gdal_grid in its current state solves my problems very well and I do not
have a pressing need for improvements). Also there is always some
trade-off between performance and flexibility, becasue I need a way to
read data from any OGR source and I need to do that programmatically
using the C API. That is certainly a thing that GRASS can't do for me
;-)

But I am open for any suggestions and criticism, the only problem is
that I can't start to fix it immediately. I can suggest to create a
ticket discribing troubles people have with the gdal_grid, so I will
have it as a permanent notice.

Best regards,
Andrey

-- 
Andrey V. Kiselev
ICQ# 26871517