These are the eastings, northings, and new elevations to modify an
existing DEM:
2295820|175258|160
2295820|175257|160
2295821|175258|160
2295821|175257|160
When I process these data the output is shifted one meter to the west.
The commands:
v.in.ascii
v.to.rast
r.patch
The output of r.patch is the file 'stuffed' and the eastings are 2295819
and 2295820.
Zooming in on the desired cells (see attached image) shows the correctly
modified cells. To get this result I increased the easting by 1 m. That is,
the data files needs eastings of 2295821 and 2295822 to correctly locate the
four changed elevations.
I ran this sequence of commands three times with the same results.
Rich
(attachments)
On Thu, Mar 23, 2017 at 10:38 PM, Rich Shepard <rshepard@appl-ecosys.com> wrote:
These are the eastings, northings, and new elevations to modify an
existing DEM:
2295820|175258|160
2295820|175257|160
2295821|175258|160
2295821|175257|160
When I process these data the output is shifted one meter to the west.
Please keep in mind that this are (I suppose) cell centers.
Hence you need to impose the computational region to 0.5 * raster
resolution larger in all directions to get the centers right.
ASCII art (needs fixed font):
+---+---+..
| x | x |
+---+---+...
...
HTH,
Markus
On Mon, Mar 27, 2017 at 10:04 PM, Markus Neteler <neteler@osgeo.org> wrote:
On Thu, Mar 23, 2017 at 10:38 PM, Rich Shepard <rshepard@appl-ecosys.com> wrote:
These are the eastings, northings, and new elevations to modify an
existing DEM:
2295820|175258|160
2295820|175257|160
2295821|175258|160
2295821|175257|160
When I process these data the output is shifted one meter to the west.
Please keep in mind that this are (I suppose) cell centers.
Hence you need to impose the computational region to 0.5 * raster
resolution larger in all directions to get the centers right.
See also
https://grass.osgeo.org/grass72/manuals/r.in.xyz.html#import-of-x,y,z-ascii-into-dem
Markus
On Mon, 27 Mar 2017, Markus Neteler wrote:
Please keep in mind that this are (I suppose) cell centers. Hence you need
to impose the computational region to 0.5 * raster resolution larger in
all directions to get the centers right.
Markus,
The cell resolution is 1.0 m so I assumed the center point would land in
the correct cell.
ASCII art (needs fixed font):
... which alpine uses.
Regards,
Rich
On Mon, 27 Mar 2017, Markus Neteler wrote:
well, it lands where you tell it to land... as determined by the current
computational region settings.
Markus,
Perhaps my technique needs improvement. This what I did:
To learn which cells needed to be identified I overlaid the raster DEM
with a point vector file, then zoomed in so I could distinguish individual
cells.
Just to the southwest of the block of 4 cells of interest was a cell with
a slightly higer elevation and a lighter color.
I noted the offsets (rows and columns) from this reference cell to the
cells of interest, then moved the raster DEM to the top of the stack.
Using the 'info' tool on the map display window I clicked on each cell in
turn and recorded the easting and northing coordinates, trucated to the
whole integer (cell dimension is 1 x 1 m).
These coordinate pairs are what I fed to v.in.ascii.
Best regards,
Rich