Hi Simon,

This may not be the best solution but a possible alternative:

I have just recently started working on a problem with similar issues of

coordinate conversion and distortion, although the spatial nature of my

problem is somewhat different from yours. I am unbending a river so that

kriging is done in a domain that follows the course of the river instead

of going over land. I have converted the coordinates (which were already

in meters and on a small scale geographically) by applying a grid

generation scheme. (Gridgen is one software that can be used).

Grid generation is widely used in the field of flow simulation in channels

or around bodies where boundary conditions apply along irregular surfaces

(hydrodynamics, aeronautics etc).

The physical boundary is defined into four segments that correspond to the

four sides of a rectangle. An equal number of grid points are laid out

along each of the pairs of facing boundaries. Various algorithms (Laplace

transforms to linear interpolation, depending on the problem) calculate

grid lines between the extreme grid point pairs. The grid is generated in

the original coordinate system, so each sample has to be assigned to the

nearest grid point within limits of resolution and coordinate precision.

In flow field simulations, the differential equations and boundary

conditions are transformed based on the mathematical relationship between

the two coordinate systems. This is not necessary in this application, as

all grid points to be estimated are calculated before kriging.

Semivarogram calculation, modeling and kriging takes place in the

transformed space and the results need merely be mapped to the original

coordinate points corresponding to the initial grid generation output.

An excellent book on the theory is:

Numerical grid generation : foundations and applications

by Thompson, Joe F. (1985)

Published New York : North-Holland : Elsevier Science Pub. Co.

Gridgen is available from Pointwise for a free 90 day trial period:

www.pointwise.com

--

*To post a message to the list, send it to

ai-geostats@....

*As a general service to list users, please remember to post a summary

of any useful responses to your questions.

*To unsubscribe, send email to

majordomo@... with no subject and

"unsubscribe ai-geostats" in the message body.

DO NOT SEND Subscribe/Unsubscribe requests to the list!