Dear all,
I am interested in extracting the longest -1,000 meter contour from a
bathymetric DEM and to save it in a text file as points.
By doing:
r.contour in=my_dem out=contour levels=-1000
v.to.points in=contour out=contour_points dmax=my_resolution
v.out.ascii in=contour_points out=contour_points.txt fs=" " dp=4
... I get a text file with the contour points, however, it includes many
different isolated contours, all with the same category (1).
Since I need only the longest, I believe I need to separate the different
contours, maybe assigning different categories somehow, then maybe updating
the database with v.to.db using option=length and then v.db.select the
longest contour.
But I am not very used to working with vectors, so I don't know if that's
the correct approach (nor how to accomplish it), so I would appreciate very
much any help.
Many thanks.
Marcello.
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Also, even when I zoom in to extract only one contour, the exported points
are not always in order in the file, in a way that when I use it to plot in
another program as a line, it connects the points in a wrong way.
How can I export contours in an amenable way to use in other programs, such
as Matlab, for instance?
Thanks in advance.
Marcello.
Marcello Gorini wrote:
Dear all,
I am interested in extracting the longest -1,000 meter contour from a
bathymetric DEM and to save it in a text file as points.
By doing:
r.contour in=my_dem out=contour levels=-1000
v.to.points in=contour out=contour_points dmax=my_resolution
v.out.ascii in=contour_points out=contour_points.txt fs=" " dp=4
... I get a text file with the contour points, however, it includes many
different isolated contours, all with the same category (1).
Since I need only the longest, I believe I need to separate the different
contours, maybe assigning different categories somehow, then maybe
updating the database with v.to.db using option=length and then
v.db.select the longest contour.
But I am not very used to working with vectors, so I don't know if that's
the correct approach (nor how to accomplish it), so I would appreciate
very much any help.
Many thanks.
Marcello.
--
View this message in context: http://osgeo-org.1803224.n2.nabble.com/How-to-extract-one-single-contour-tp6639491p6641376.html
Sent from the Grass - Users mailing list archive at Nabble.com.