I am currently trying to get a 3D kriging to run using the KT3D program

from GSLIB. I have managed to run a 2D version of this with no problems,

but I just can't seem to work out the 3D implementation. My data is a

set of time vectors from 113 weather stations across central Oregon.

I have successfully run space-only 2D runs, using Monthly or Annual

averages for each of the stations. Details of the 2D run can be seen on

my website:

http://www.geos.ed.ac.uk/homes/s0198247/Geostats.html

Please forgive anything which is apocriphal/stupid on this page

(feedback very welcome).

The variogram was developed in space by taking the average of the

spatial variograms for each monthly averaged dataset (average of 48

variograms), as calculated by GeoR, and incorporating an elevation

trend. The temporal variogram was calculated from the "flattened" and

averaged data (altitude trend removed). I have managed to derive an

anisotropic variogram which will describe the spatiotemporal variation,

using the techniques suggested in the GSLIB manual - zonal anisotropy is

handled by setting some structures very long or short ranges to mask

their effects in certain directions. However, I think perhaps it is this

which is causing my problem: When I come to run a 3D implementation,

most of my grid is no-data (-999). The debug file says something like

singular matrix for these points? Should I try to model the variogram as

a seperable space-time system rather than a single 3D ellipsoid? Any

help with this would be hugely appreciated.

Here are some relevant bits of my parameter file, for those who are

interested:

Grid Definition:

98 562.6186 1.0 -nx,xmn,xsiz

86 4903.722 1.0 -ny,ymn,ysiz

1827 1.0 1.0 -nz,zmn,zsiz

My coordinate system is spatial in the x and y directions (UTM zone 10,

measured in km), but temporal in the vertical (z) direction. The time

step is measured in days. My grid is therefore 98 x 86 = 8,428 square

kilometres, by 1827 days = 15,397,956 grid squares.

Search ellipsoid:

250.0 250.0 30.0 -maximum search radii

0.0 0.0 0.0 -angles for search ellipsoid

Am I right in thinking this means x_radius = 250 km, y_radius = 250 km,

z_radius = 30 days?

Variogram:

3 0.0 -nst, nugget effect

1 5.5 0.0 0.0 0.0 -it,cc,ang1,ang2,ang3

3000.0 3000.0 5.8 -a_hmax, a_hmin, a_vert

1 2.2 0.0 0.0 0.0 -it,cc,ang1,ang2,ang3

0.001 0.001 10000.0 -a_hmax, a_hmin, a_vert

2 1.0 0.0 0.0 0.0 -it,cc,ang1,ang2,ang3

68.0 68.0 16.8 -a_hmax, a_hmin, a_vert

Here I have no nugget effect, as the temporal variogram doesn't display

a nugget effect. I attempt to impose an anisotropic nugget effect with

the vary short scale structure. The teporal variogram has a much higher

sill than the spatial variogram, so I impose this using very long ranges

on the first spherical structure for the spatial dimensions. Is this

appropriate? Should I specify these in order of max to min range, and

use rotations (eg for the second structure ang2 = 90, and ranges 10000,

0.001, 0.001)?

Many thanks

Luke Spadavecchia