My current topographic vector data file has a column name for the elevation
data, ContourEle. Reading the v.to.rast page there is a use parameter (with
'z' for elevation) and an attribute_column parmater. Because the vector
map's database table does not have a column named 'z', but the one named
'CountourEle' I put both parameters on the command line.
grass told me that I cannot have both, and that using the named elevation
column was not allowed. So I put 'use=z' in the command and the conversion
worked.
How did v.to.rast know that the column named 'ContourEle' was the z value?
Should the manual page explain that the use and attribute_column cannot be
used together for elevation? And, when the attribute_column would be
appropriate?
Regards,
Rich
Sounds like the vector geometry was already 3D, that’s the case when you use use=z. If the vector would be 2D (see v.info) you would have to use the attribute table.
On Wed, May 10, 2023 at 12:14 PM Rich Shepard <rshepard@appl-ecosys.com> wrote:
My current topographic vector data file has a column name for the elevation
data, ContourEle. Reading the v.to.rast page there is a use parameter (with
‘z’ for elevation) and an attribute_column parmater. Because the vector
map’s database table does not have a column named ‘z’, but the one named
‘CountourEle’ I put both parameters on the command line.
grass told me that I cannot have both, and that using the named elevation
column was not allowed. So I put ‘use=z’ in the command and the conversion
worked.
How did v.to.rast know that the column named ‘ContourEle’ was the z value?
Should the manual page explain that the use and attribute_column cannot be
used together for elevation? And, when the attribute_column would be
appropriate?
Regards,
Rich
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On Wed, 10 May 2023, Anna Petrášová wrote:
Sounds like the vector geometry was already 3D, that's the case when you
use use=z. If the vector would be 2D (see v.info) you would have to use the
attribute table.
Anna,
When I used the 2D file, regardless of which parameter I used or both,
v.to.rast told me the file was not 3D. That's why I converted it. When
'use=z' failed I tried 'attribute_column=ContourEle' with the same result.
Now I have the rasterized contour map (image attached) and need to learn how
to use it to create flowlines, flow accumulations, and more. It does not
have the 1'x1' cells each with a color representing the elevation.
Is there an r.* module to interpolate elevations between the contour lines
so I have cells?
This is all new to me so I appreciate all the help I get.
Regards,
Rich
(attachments)
On Wed, 10 May 2023, Rich Shepard wrote:
Is there an r.* module to interpolate elevations between the contour lines
so I have cells?
There are several r.resamp.* modules in the core distribution. Please advise
me which would be most appropriate for my rasterized contour elevation map.
TIA,
Rich
On Wed, 10 May 2023, Rich Shepard wrote:
There are several r.resamp.* modules in the core distribution. Please advise
me which would be most appropriate for my rasterized contour elevation map.
Should I use one of the v.surf.* modules then re-rasterize the resulting
map? If so, please recommend the most appropriate v.surf.* module and
recommended parameters to use.
TIA,
Rich
On Wed, May 10, 2023 at 12:34 PM Rich Shepard <rshepard@appl-ecosys.com> wrote:
On Wed, 10 May 2023, Anna Petrášová wrote:
Sounds like the vector geometry was already 3D, that’s the case when you
use use=z. If the vector would be 2D (see v.info) you would have to use the
attribute table.
Anna,
When I used the 2D file, regardless of which parameter I used or both,
v.to.rast told me the file was not 3D. That’s why I converted it. When
‘use=z’ failed I tried ‘attribute_column=ContourEle’ with the same result.
Now I have the rasterized contour map (image attached) and need to learn how
to use it to create flowlines, flow accumulations, and more. It does not
have the 1’x1’ cells each with a color representing the elevation.
Is there an r.* module to interpolate elevations between the contour lines
so I have cells?
There is r.surf.contour, so that sounds like the tool you need.
This is all new to me so I appreciate all the help I get.
Regards,
Rich_______________________________________________
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On Wed, 10 May 2023, Anna Petrášová wrote:
There is r.surf.contour, so that sounds like the tool you need.
Thank you, Anna. I'll re-do the process.
Best regards,
Rich