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Occasional Contributor
Posts: 10
Registered: ‎03-29-2016

Spatial Recipe-Correlation

Hi,

 

I am trying to creat a spatial model for drought monitoring using Land Surface Temperature(LST) model and NDVI. However I am unable to create a correlation between LST and NDVI using spatial modeler. Any idea on how to correlate the two output.

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Technical Evangelist
Posts: 662
Registered: ‎02-02-2016

Re: Spatial Recipe-Correlation

Can you attach your spatial model?

 

Thanks,

 

Stephen Bent

Hexagon Geospatial Support

 

Highlighted
Occasional Contributor
Posts: 10
Registered: ‎03-29-2016

Re: Spatial Recipe-Correlation

Find attached the model. I am interested in  a model for estimating and predicting drought but I am unable to Correlate LST and NDVI.

Highlighted
Occasional Contributor
Posts: 10
Registered: ‎03-29-2016

Re: Spatial Recipe-Correlation

Any Ideas

Highlighted
Technical Evangelist
Posts: 662
Registered: ‎02-02-2016

Re: Spatial Recipe-Correlation

You could use the Correlation operator at the end of your model. This operator will return a correlation matrix of the layers in the input raster. You will need to stack the temperature raster and the NDVI raster together first as illustrated in the example below.

 

correlation_sm.jpg


Regards,

 

Stephen Bent
Hexagon Geospatial Support

Highlighted
Occasional Contributor
Posts: 10
Registered: ‎03-29-2016

Re: Spatial Recipe-Correlation

THank you for your input Stephen,

 

Can the model be modified to generate a spatial matrix raster output.

 

Regads

 

Silas

Highlighted
Technical Evangelist
Posts: 662
Registered: ‎02-02-2016

Re: Spatial Recipe-Correlation

Can you elaborate on what a spatial matrix raster output should look like?

 

Regards,

 

Stephen Bent

Hexagon Geospatial Support

 

Highlighted
Occasional Contributor
Posts: 10
Registered: ‎03-29-2016

Re: Spatial Recipe-Correlation

Hi Stephen,

 

I  modified the model as proposed and run. The output was a an MTX file but what i had in mind as the output is a raster image showing areas having positive or negative correlation of the two variables. Find attached the modified model.

 

Regards

 

Silas

 

Highlighted
Occasional Contributor
Posts: 10
Registered: ‎03-29-2016

Re: Spatial Recipe-Correlation

Hi,

 

Any ideas?

 

 

Highlighted
Technical Evangelist
Posts: 662
Registered: ‎02-02-2016

Re: Spatial Recipe-Correlation

It may be possible to output a raster image showing areas of positive or negative correlation, but it won’t be easy. How would the different areas showing positive or negative correlation be defined? I suppose you could perform an unsupervised classification or image segmentation to define the regions. You would need to separate each class or segment into its own raster object to calculate the correlation between NDVI and temperature for that area. Then you would have to write the resulting correlation value to the pixels for each raster object that represents a class or segment and finally piece all of the individual raster objects back together again.

 

Regards,

 

Stephen