I've got a vector track for a vehicle. How do I convert it into a
raster of coverage assuming a given perpendicular spread?
I know that s.to.rast can be used to create a raster where each site
is expanded into multiple cells. But that is only useful if one assumes
a circular(?) coverage at each point.
Also, in the case of chemical application, the rate of application
depends on the speed of the vehicle ... and even the rotation caused
by turning.
Are there programs in GRASS that handle this?
--
James Cameron mailto:quozl@us.netrek.org http://quozl.netrek.org/
On Tue, May 30, 2000 at 11:16:49AM +1000, James Cameron wrote:
I've got a vector track for a vehicle. How do I convert it into a
raster of coverage assuming a given perpendicular spread?
I know that s.to.rast can be used to create a raster where each site
is expanded into multiple cells. But that is only useful if one assumes
a circular(?) coverage at each point.
What about v.to.rast? That is, you have a vector line (don't build
areas!), you convert it to a raster with v.to.rast and then you make the
raster grow to match the application spread.
Also, in the case of chemical application, the rate of application
depends on the speed of the vehicle ... and even the rotation caused
by turning.
Hmm, more difficult. I see where the application would be greater on the
inside of a curve than the outside, and would be dependent on the angle
of the curve (overlap). Perhaps this is a job for mapcalc? Is the vector
track over regular units in time, or is it continuous with a speed
element?
Are there programs in GRASS that handle this?
I don't know, think you'll need to roll your own. Perhaps by using a
series of additive matrix filters on the original points. I suppose
they'd have to be applied in order of the track so that the direction of
the vehicle can be accounted for. Sorry, for the non-answer.
Interesting problem 
Please post the solution when you find it.
--
¶ One·should·only·use·the·ASCII·characterset·when·compos
» ing·email·messages.
On Mon, May 29, 2000 at 07:50:26PM -0700, Eric G . Miller wrote:
What about v.to.rast? That is, you have a vector line (don't build
areas!), you convert it to a raster with v.to.rast and then you make the
raster grow to match the application spread.
Yes, I see. r.grow is the one to use.
Hmm, more difficult. I see where the application would be greater on the
inside of a curve than the outside, and would be dependent on the angle
of the curve (overlap). Perhaps this is a job for mapcalc? Is the vector
track over regular units in time, or is it continuous with a speed
element?
Over regular units in time, I think. The GPS gives me an x/y location
every second. From that it (or I) can calculate the speed.
To make a linear spread, I could r.mapcalc "add" the original map to
the r.grow output. Then do it again a few times.
--
James Cameron mailto:quozl@us.netrek.org http://quozl.netrek.org/