Hi everybody I'm writing a diploma thesis about error propagation in digital terrain models and I want to use monte carlo methods to simulate elevation errors in the data points and their effect on various gis operations.
My data are irregularly distributed points (not grid data!) which I triangulated using java as programming language. I found lots of suggestions in literature how to simulate autocorrelated error fields (Heuvelink, Ehlschlaeger, Goodchild, Wechsler, Haining/Griffith/Bennet) but as far as I was able to understand them the only practicable two (for my task) where: 1) Generating uncorrelated random field and swapping until a predefined level of autocorrelation (Moran's I) is reached. (Goodchild, 1980) 2) Same as 1) but prior to swapping the random numbers have to pass a series of statistical tests like a test for multivariate-normality. (Haining, Griffith, Bennet, 1983) Am I right saying that I need measured errors at some points if i want to apply interpolation techniques to simulate an autocorrelated error field? (Ehlschlaeger (1994) used a formula depending on the spatial autocorrelative effect) I'm asking that, because the only thing I have is the RMSE which is 0.4 m. I haven't got the points from which this error was empirically derived. But I could randomly set a few start points and derive all other points from them. So my first question is: What technique shall I apply to simulate an autocorrelated random error field? My second set of questions is: How can I determine suitable parameters for the error fields autocorrelation? What is the minimum distance of spatial independence? How should I determine a suitable distance decay exponent if I haven't got any sample error points to estimate a variogram from? I hope my questions are not too stupid and thanks for any help! Marcel -- * To post a message to the list, send it to [EMAIL PROTECTED] * As a general service to the users, please remember to post a summary of any useful responses to your questions. * To unsubscribe, send an email to [EMAIL PROTECTED] with no subject and "unsubscribe ai-geostats" followed by "end" on the next line in the message body. DO NOT SEND Subscribe/Unsubscribe requests to the list * Support to the list is provided at http://www.ai-geostats.org
