Continuing my small quest with kml files... and bombing you with simple
questions ;-p
are kml files carrying topology information besides coordinates?
I needed to manually correct a kml file which looked very bad after
importing in GRASS (with -c otherwise it was not useful!)
Automatic cleaning is really not useful even after trying to feed with
logical thresholds the various tools.
Cheers,
Nikos
On Tuesday 26 February 2008, Nikos Alexandris wrote:
Continuing my small quest with kml files... and bombing you with simple
questions ;-pare kml files carrying topology information besides coordinates?
I doubt it. As far as I know they are just "simple features".
I needed to manually correct a kml file which looked very bad after
importing in GRASS (with -c otherwise it was not useful!)
i am not surprised that a KML file resulted in a topologically broken file.
These days everyone and their brother are creating KML via all sorts of
methods-- most of which have little notion/concern for
topological-correctness.
Automatic cleaning is really not useful even after trying to feed with
logical thresholds the various tools.
Try opening the file with v.digit and look for oddities.
Cheers,
Nikos
Dylan
--
Dylan Beaudette
Soil Resource Laboratory
http://casoilresource.lawr.ucdavis.edu/
University of California at Davis
530.754.7341
On Thu, 2008-02-28 at 09:15 -0800, Dylan Beaudette wrote:
Thank you for your reply Dylan!
On Tuesday 26 February 2008, Nikos Alexandris wrote:
> Continuing my small quest with kml files... and bombing you with simple
> questions ;-p
>
> are kml files carrying topology information besides coordinates?I doubt it. As far as I know they are just "simple features".
>
> I needed to manually correct a kml file which looked very bad after
> importing in GRASS (with -c otherwise it was not useful!)i am not surprised that a KML file resulted in a topologically broken file.
These days everyone and their brother are creating KML via all sorts of
methods-- most of which have little notion/concern for
topological-correctness.
+1
> Automatic cleaning is really not useful even after trying to feed with
> logical thresholds the various tools.Try opening the file with v.digit and look for oddities.
Had to correct (almost) everything. Tha data are supposed to come from a
GPS measurement session.
All polygons were open after importing in GRASS. Yet there were
centroids inside this virtually closed boundaries. And the strange thing
is that one (call it) centroid was out of the virtual boundaries...
Don't know, maybe my mistake for this last statement about the centroid
falling out.
Cheers!
On Thursday 28 February 2008, Nikos Alexandris wrote:
On Thu, 2008-02-28 at 09:15 -0800, Dylan Beaudette wrote:
Thank you for your reply Dylan!
> On Tuesday 26 February 2008, Nikos Alexandris wrote:
> > Continuing my small quest with kml files... and bombing you with simple
> > questions ;-p
> >
> > are kml files carrying topology information besides coordinates?
>
> I doubt it. As far as I know they are just "simple features".
>
> > I needed to manually correct a kml file which looked very bad after
> > importing in GRASS (with -c otherwise it was not useful!)
>
> i am not surprised that a KML file resulted in a topologically broken
> file. These days everyone and their brother are creating KML via all
> sorts of methods-- most of which have little notion/concern for
> topological-correctness.+1
> > Automatic cleaning is really not useful even after trying to feed with
> > logical thresholds the various tools.
>
> Try opening the file with v.digit and look for oddities.
Hi,
Had to correct (almost) everything. Tha data are supposed to come from a
GPS measurement session.
I would think that the results from such as session be points or lines...
All polygons were open after importing in GRASS. Yet there were
centroids inside this virtually closed boundaries. And the strange thing
is that one (call it) centroid was out of the virtual boundaries...
I wonder where the polygons came from -- could it be that one of the import
steps mistook the geometry in KML file as polygons? Line data that are
interpreted as polygons---especially in the presence of overlapping
features---would definitely cause some craziness.
Don't know, maybe my mistake for this last statement about the centroid
falling out.Cheers!
Have the original data on hand?
Dylan
--
Dylan Beaudette
Soil Resource Laboratory
http://casoilresource.lawr.ucdavis.edu/
University of California at Davis
530.754.7341
On Thu, 2008-02-28 at 09:23 -0800, Dylan Beaudette wrote:
On Thursday 28 February 2008, Nikos Alexandris wrote:
> On Thu, 2008-02-28 at 09:15 -0800, Dylan Beaudette wrote:
>
> Thank you for your reply Dylan!
>
> > On Tuesday 26 February 2008, Nikos Alexandris wrote:
> > > Continuing my small quest with kml files... and bombing you with simple
> > > questions ;-p
> > >
> > > are kml files carrying topology information besides coordinates?
> >
> > I doubt it. As far as I know they are just "simple features".
> >
> > > I needed to manually correct a kml file which looked very bad after
> > > importing in GRASS (with -c otherwise it was not useful!)
> >
> > i am not surprised that a KML file resulted in a topologically broken
> > file. These days everyone and their brother are creating KML via all
> > sorts of methods-- most of which have little notion/concern for
> > topological-correctness.
>
> +1
>
> > > Automatic cleaning is really not useful even after trying to feed with
> > > logical thresholds the various tools.
> >
> > Try opening the file with v.digit and look for oddities.Hi,
> Had to correct (almost) everything. Tha data are supposed to come from a
> GPS measurement session.I would think that the results from such as session be points or lines...
Probably. GPS measurement from a Forest Service office in Greece. I am
not saying it ironically, but not everybody knows how and, even worse,
takes the time to set-up a GPS session properly... and this could be the
case.
> All polygons were open after importing in GRASS. Yet there were
> centroids inside this virtually closed boundaries. And the strange thing
> is that one (call it) centroid was out of the virtual boundaries...I wonder where the polygons came from -- could it be that one of the import
steps mistook the geometry in KML file as polygons? Line data that are
interpreted as polygons---especially in the presence of overlapping
features---would definitely cause some craziness.
Fire, as known, was for Greece a Tragedy this summer. There is a private
initiative from somebody doing a great job: collecting burnt area's and
publishing under GPL in kml formats. It's a great job from all kinds of
aspects (political, social, etc). Of course this is not the place to
extend the discussion about this.
However,
I discovered that importing a kml file of my interest (finally) in GRASS
didn't show me what I expected to see.
> Don't know, maybe my mistake for this last statement about the centroid
> falling out.
>
> Cheers!Have the original data on hand?
One example http://tilaphos.blogspot.com/2008/01/blog-post_30.html
The kml file I am talking about is (for which it is stated that it's
only a rough estimation of burned areas):
http://tilaphos.googlepages.com/Korinthia_estimate_2007.kmz
(there are lot's of kml's.. all of them referering to burned areas)
I am about to prepare a small step-by-step guide on how to import kml's
in GRASS. I got support from the man who run's the blog as well.
I would like to point out some basics about topology, shapefiles and kml
files. Of course I am not the Expert on all but a some remarks I could
provide to improve future GPS sessions.
If you are interested more I can play the translator.
On Thu, 2008-02-28 at 18:36 +0100, Nikos Alexandris wrote:
[...]
One example http://tilaphos.blogspot.com/2008/01/blog-post_30.html
The kml file I am talking about is (for which it is stated that it's
only a rough estimation of burned areas):
http://tilaphos.googlepages.com/Korinthia_estimate_2007.kmz
Sorry,
it's the file above the one I mentioned in my previous mail, that is:
http://tilaphos.googlepages.com/Korinthia_2007.kmz
Just in case...
Greetings!