Correlation between Rasters? Raster Validation?

[KathrinSchulte-Braucks]

Hey,

I have several raster files which I'd like to analyze concerning their level of similarity / correlation. What's the best way doing this? Apparently, Geostatistical Analyst only works with Vector Data. So do I have to apply the formula manualy with Map Algebra or is there a predefined tool e.g. for Pearson correlation or cross validation of raster files?

Thanks,

Kathrin

[FrankHanssen]

You could also convert the rasters to points, join the points by location, and run the Ordinary Least Squares tool in Spatial statistics.  Testing the significance of the coefficient in the linear model is the same as testing the correlation.

This seems to be the solution I need! I have modelled land surface clutter (as GRID) and I want to compare the modelled clutter GRID with the radar detected land cluttermap (GRID) from the same area. As I am a newbee to regression analysis I therefore need to clairfy some details.

I have converted both GRID`s to points and joined them using Spatial Join in my model like you described. I need to test the relationships in two ways:

* First: I want to compare the relationship between modeled values and radar detected values in the two datasets. When using OLS is it correct to use the modelled values as "Dependent variables" and the radar detected values as "Explanatory variables"?

* Seccond: I also want to perform a binary test to find the spatial relationship between modelled clutter (1= Present, 0= Non- present) and the radar detected values  (1= Present, 0= Non- present). Can I use OLS also for this purpose or should I use a different tool?

Best regards

Frank Hanssen
GIS- analyst
NINA

[EricKrause]

* First: I want to compare the relationship between modeled values and radar detected values in the two datasets. When using OLS is it correct to use the modelled values as "Dependent variables" and the radar detected values as "Explanatory variables"?

It doesn't matter which you call the dependent and explanatory variables.  The p-value of the coefficient should be the same either way.

* Seccond: I also want to perform a binary test to find the spatial relationship between modelled clutter (1= Present, 0= Non- present) and the radar detected values  (1= Present, 0= Non- present). Can I use OLS also for this purpose or should I use a different tool?

You can use the same tool to get the correlation, but you won't be able to trust the p-value.

We don't have a specific tool for it, but if you need to test the correlation of two binary variables, use the Phi Coefficient of Correlation.  You can probably write a Python script to calculate and test it for you, but it won't be simple.

[SandraMelzner]

I would like to compare as well two rasters. I tried to use Band collection statistics, but I can't open the resulting .asc in Arc Map!

I am quiet "virgin" in the statistical analysis of rasters! It could be that I need another function...??

My problem:
I have two raster with rockfall trajectories of different extent and different energy values. If you overlay these two rasters there are pixels,where eather one of the rasters has values OR there are pixels where both rasters have values, which are differnt from each other (these trajectories look a little bit like flow accumulation outputs)! So far I analized the data in substracting one from the other- differences are shown in different colours!
What kind of analysis could I use instead of this simple aproach?
Thanxxx 🙂

[KathrinSchulte-Braucks]

@ ING2011: Open the resulting file with a text editor.

[PaulLeonard]

Convert Rasters to Points,

Unfortunately this is not a viable option for large grids.

[champikakariyawasam]

I use high resolution 30s global asc raster layers for maxent modeling. I need to remove correlated variables, but none of the tools worked due to memory problems (exceed python limits). can somebody advise me pl? when i used 10m as files it worked well. Can i check the correlated variables using 10m data and select variables and go for my 30s data for modeling? can somebody instruct me pl?