[GRASS-user] Surface

[Raphael Saldanha]

Hi!

I have a shapefile loaded in grass, as a 3D Vector:

+----------------------------------------------------------------------------+
 | Layer:           pontos2 at PERMANENT
|
 | Mapset:
PERMANENT                                                 |
 | Location:
altimetria_Porcos                                         |
 | Database:        C:/GRASS GIS DataBase                             |
 |
Title:                                                                     |
 | Map scale:
1:1                                                       |
 | Map format:
native                                                    |
 | Name of creator:
plangeo                                                   |
 |
Organization:                                                              |
 | Source date:     Wed Sep 10 10:31:28
2008                                  |
 |----------------------------------------------------------------------------|
 |   Type of Map:  vector (level:
2)                                          |
 |
|
 |   Number of points:       6913            Number of areas:
0          |
 |   Number of lines:        0               Number of islands:
0          |
 |   Number of boundaries:   0               Number of faces:
0          |
 |   Number of centroids:    0               Number of kernels:
0          |
 |
|
 |   Map is 3D:
1                                                |
 |   Number of dblinks:
1                                                |
 |
|
 |         Projection: Universe Transverse Mercator (zone
0)                  |
 |               N:       7834144.073    S:
7833041.84504481                 |
 |               E:   441953.15895164    W:
440981.71795164                 |
 |               B:                 0    T:
732.748                 |
 |
|
 |   Digitization threshold:
0                                                |
 |
Comments:                                                                |
 |
|
 +----------------------------------------------------------------------------+

And a column, named "Elevation":

column:Elevation
description:
type:DOUBLE PRECISION
len:20
scale:6
precision:18
default:
nullok:yes
select:yes
update:yes

I need to create countour... so, I think, I must interpolate a surface from
this points making something like a DEM, and after, interpolate the
contours... Is this correct?

Now, I'm trying to interpolate a suface with IDW (very slow...)

v.surf.idw input=pontos2 at PERMANENT output=teste npoints=12 layer=1
column=elevation --overwrite

Another question: what is the precision of this surface? What contour
interval can I generate?

Regards,

Raphael Saldanha
BRAZIL
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