Dear list,
First, I would like to say thank you to
Gregoire for keeping this list alive.
I'm trying to do "risk assessment", and I
have some questions about risk assessment with Gaussian Simulation:
(1) How to produce a probability
map?
With Gaussian simulation, we can produce
many maps/realisations, e.g., 100. Based on the 100 maps, a probability map
of higher than a threshold can be produced. I wonder how to
produce such a probability map? My understanding is that for each pixel, we just
count how many values out of the 100 are >threshold, and the number is
regarded as the "probability". Am I right? It seems that this is a
time consuming procedure with GIS map algebra. Are there any suggestions for a
quick calculation?
(2) Is a probability map better than a
Kriging interpolated map for the purpose of risk assessment?
(3) Is "PCLASS" function in IDRISI 32
Release 2 better/easier than the probability map from Gaussian
simulation?
From the online help of IDRISI 32 R2,
Section "Kriging and Simulation Notes", it says "If the final goal of
simulated surfaces will be to directly reclassify the surfaces by a threshold
value, and calculate a probability of occurrence for a process based on that
threshold, conditional simulation may be unnecessary. Instead kriging and
variance images may be created and then used together with PCLASS." Any
comments?
(4) How to carry out "PCLASS"?
Following the above question, I have a
problem in doing PCLASS. I cannot input the file name of Kriging variance to the
field of "Value error" of the documentation file. It seems that this
field only accepts a "value", not an "image file name" or anything in text.
Anyone has the experience?
Cheers,
Chaosheng Zhang
=================================================
Dr. Chaosheng Zhang Lecturer in GIS Department of Geography National University of Ireland Galway IRELAND Tel: +353-91-524411 ext. 2375
Fax: +353-91-525700 Email: [EMAIL PROTECTED] [EMAIL PROTECTED] Web: http://www.nuigalway.ie/geography/zhang.html ================================================= |
- Re: AI-GEOSTATS: Risk Assessment with Gaussian Si... Chaosheng Zhang
- Re: AI-GEOSTATS: Risk Assessment with Gaussi... Pierre Goovaerts
- Re: AI-GEOSTATS: Risk Assessment with Ga... Chaosheng Zhang
- Re: AI-GEOSTATS: Risk Assessment with Gaussi... Brian R Gray
- Re: AI-GEOSTATS: Risk Assessment with Ga... Pierre Goovaerts
- RE: AI-GEOSTATS: Risk Assessment with Gaussi... McKenna, Sean A
- AI-GEOSTATS: Risk Assessment with Gaussi... Isobel Clark
- Re: AI-GEOSTATS: Risk Assessment with Ga... Chaosheng Zhang
- RE: AI-GEOSTATS: Risk Assessment with Gaussi... Syed Abdul Rahman Shibli
- Re: AI-GEOSTATS: Risk Assessment with Ga... Chuck Ehlschlaeger