My data is indeed a point cloud from bathymetry data so I can understand the problems you outlined so I will be happy to create 3d output from the multiple slicing method of r.to.rast3. I have only previously set a 2d region which all points lie within but am unsure how to set a 3d region?
I ‘successfully’ ran the v.vol.rst command with my DOC data by specifying the w column as you suggested though it turns out the data is not sufficient in terms of density and it does in fact say points are outside 2d/3d region.
Apologies for all these questions. I am still new to GRASS.
Date: Thu, 21 Aug 2008 12:37:40 +0100
From: benjamin.ducke@oxfordarch.co.uk
To: i.summers@hotmail.co.uk
Subject: Re: [GRASS-user] displaying volumes from xyz vector in nvizIf what you are after is the actual shape of the loch in voxel space:
that is not easy to do with current GRASS tools.
I do not know what your input data looks like, but I assume it is a
point cloud derived from bathymetry data? If so, then what you have
is a cloud of point describing the exterior hull of the loch. In order
to convert this to a voxel object, GRASS would need to be able to first
construct the polygonal hull using these points and then convert that
to a voxel representation. This is not currently possible and would
require someone to put some serious effort into creating a module
with the capability to convert 3D vector polygons to volumetric voxel
representations.I have never heard about the ‘position not in queue’ message. No idea
what is going wrong there.v.vol.rst should work fine if you use the ‘wcolumn=’ option to specify
the name of the attribute you want to interpolate.Have you set the 3D region extents correctly to cover your 3D input
data and produce the number of slices you want?Ben
ian summers wrote:
Hello Ben,
Thank you for your suggestion but when I attempt to run r,to.rast3 I get
the ‘position not in queue’ message again. I ran v.kernel on the
respective slices with st deviation of 5 leaving all other parameters as
they were. Was this correct? Having used the v.info command the layers
are 3D. Essentially what I am trying to achieve is a volume cube of loch
lomond from x, y, z coordinates.I also have dissolved organic carbon data which i was hoping to display
volumetrically within this that has x, y, z, DOC columns. I ran
v.vol.rst but it says w column not supported. my data here is:-INTEGER/cat
INTEGER/Id
DOUBLE PRECISION/X
DOUBLE PRECISION/Y
DOUBLE PRECISION/Z
DOUBLE PRECISION/DOCMy main focus is the volume cube of loch lomond. The DOC would be a bonus.
Ian
Date: Thu, 21 Aug 2008 09:55:07 +0100
From: benjamin.ducke@oxfordarch.co.uk
CC: grass-user@lists.osgeo.org
Subject: Re: [GRASS-user] displaying volumes from xyz vector in nvizTo generate a volumetric model of your point data, you need to use
an algorithm that can interpolate an attribute in 3D space.To start with, you need to make sure that your input points map is
actually a 3D geometry, not just 2D points with X,Y and Z attributes
attached (us v.info to find out).v.to.rast3 simply takes the 3D point positions and creates a single
voxel value at every point location in the input map. Most likely, this
is not what you want and you should look into v.vol.rst instead.The question then is WHAT to interpolate. In your attribute table list
below, I cannot see an attribute that could actually be used for
interpolation. The only thing you have are integer categories.If you want to show point density in 3D: there is currently no GRASS
module to calculate that. So the only thing you can do is calculate
density for 2D slices at different Z ranges separately (use v.select
to query out points for each Z range, then run v.kernel on them) and
stack the resulting 2D raster maps on top of each other to form a voxel
cube using r.to.rast3.Ben
ian summers wrote:
Dear all,
I have a vector point file and have tried to run the program
v.to.rast3
though in the ‘column name’ section I am unsure what to enter? the
column attributes for the data are as follows.INTEGER/cat
INTEGER/Id
DOUBLE PRECISION/X
DOUBLE PRECISION/Y
DOUBLE PRECISION/ZI have tried entering cat, id and z in this box but in the output I
receive the message ‘position not in queue’.I have also tried to create the volume using r.to.rast3 and though it
appears as though a file is created when it comes to display in nviz
only a plain 2D white tile appears. The values in my Z column are
negative as I am modelling a lake. I am unsure whether this holds any
bearing on outcome.Hope someone can help.
Ian Summers
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Benjamin Ducke
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Janus House
Osney Mead
OX2 0ES
Oxford, U.K.Tel: +44 (0)1865 263 800 (switchboard)
Tel: +44 (0)1865 980 758 (direct)
Fax :+44 (0)1865 793 496
benjamin.ducke@oxfordarch.co.uk
Files attached to this email may be in ISO 26300 format (OASIS Open Document Format). If you have difficulty opening them, please visit http://iso26300.info for more information.
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