[GRASSLIST:6168] Re: v.mkgrid problems again...

[Dylan Beaudette]

Radim,

Thank you for the reply... but I don't quite understand how this will affect 
the operation of v.mkgrid. (sorry i am little dense sometimes!)

Will the newer version of GRASS include v.mkgrid that will produce areas?

Thank you very much for looking at this, it is a really nice module!

Oh, and it looks like in my original email, the Mac OS and Linux output from 
v.mkgrid were reversed...!

-- 
Dylan Beaudette
Soils and Biogeochemistry Graduate Group
University of California at Davis
530.754.7341

On Monday 14 March 2005 12:50 am, Radim Blazek wrote:
> The horizontal lines are divided by 3:
> /*
> * For latlon, must draw in shorter sections
> * to make sure that each section of the grid
> * line is less than half way around the globe
> */
>
> and horizontal lines are written in loop:
> x_len = length/3.;
> for () {
>      next_x = x + x_len;
> }
>
> and to get exactly the same value for verticals
> for () {
>      x += x_len;
>      x += x_len;
>      x += x_len;
> }
>
> I guess that compiler can optimize the verticals to
> x += 3*x_len; and the result will be different.
>
> I have changed that for horizontals in HEAD branch to
> x = startx;
> for (j = 0; j < 3; j++)
> {
>     if ( j < 2 )
>        next_x = x + x_len;
>     else
>        next_x = startx + length;
> }
> and verticals
> for () {
>      x += length;
> }
>
> which should always give that same value for grid nodes.
>
>
> Radim
>
> Dylan Beaudette wrote:
> > Hi everyone,
> >
> > last month I was having some trouble with v.mkgrid producing boundaries,
> > centroids, but no areas... after upgrading to GRASS6-beta1 the problem
> > was solved. Now with the latest GRASS 6.0.0 source v.mkgrid is not
> > producing areas. As a comparison, the GRASS6 package for MacOS X
> > produces the correct output.
> >
> > Here is a comparison of the output:
> >
> > MacOS X Package version of GRASS6:
> > ---------------------
> > GRASS 6.0.0 (pinn):~ > v.mkgrid map=g grid=3,3 ; d.vect g
> > Creating vector grid ...
> > Writing out vector rows ...
> > Writing out vector columns ...
> > Creating centroids ...
> > Building topology ...
> > 57 primitives registered
> > Building areas:  100%
> > 0 areas built
> > 0 isles built
> > Attaching islands:
> > Attaching centroids:  100%
> > Topology was built.
> > Number of nodes     :   61
> > Number of primitives:   57
> > Number of points    :   0
> > Number of lines     :   0
> > Number of boundaries:   48
> > Number of centroids :   9
> > Number of areas     :   0
> > Number of isles     :   0
> > Number of incorrect boundaries   :   48
> > Number of centroids outside area :   9
> > ---------------------
> >
> > GRASS 6.0.0 on linux from source code:
> > ---------------------
> > GRASS 6.0.cvs:~ - spearfish57 > v.mkgrid map=g grid=3,3
> > Creating vector grid ...
> > Writing out vector rows ...
> > Writing out vector columns ...
> > Creating centroids ...
> > Building topology ...
> > 57 primitives registered
> > Building areas:  100%
> > 9 areas built
> > 1 isles built
> > Attaching islands:  100%
> > Attaching centroids:  100%
> > Topology was built.
> > Number of nodes     :   49
> > Number of primitives:   57
> > Number of points    :   0
> > Number of lines     :   0
> > Number of boundaries:   48
> > Number of centroids :   9
> > Number of areas     :   9
> > Number of isles     :   1
> > ---------------------
> >
> >
> > Any ideas on why this is happening?
> >
> > Thanks in advance!
> >
> > Dylan