Applying a formula to more than two Raster Layers

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Applying a formula to more than two Raster Layers

David Westcott

Dear Post GIS Users

 

Is there a way in PostGIS of applying a formula to more than two Raster layers?

 

For example, I want to derive a new Raster Layer calculated as follows:

 

Constant1 x Layer1 x (Layer2 ^ Constant2) + Constant3 x Layer3 x (Layer4 ^ Constant4) + Constant5 x Layer5 x (Layer6 ^ Constant6)

 

Where  Constant1, Constant2, Constant3, Constant4, Constant5 & Constant6 are fixed constants.

                Layer1, Layer2, Layer3, Layer4, Layer5 & Layer6 are already derived Raster Layers.

                The ‘^’ sign represents raised to the power of. (i.e. 3^2 = 9).

 

How would I apply such a formula in PostGIS?

 

Kind Regards

 

David Westcott

 


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Re: Applying a formula to more than two Raster Layers

David Haynes
You can use the map algebra function combined with Common Table expressions.


On Tue, May 9, 2017 at 4:20 AM, David Westcott <[hidden email]> wrote:

Dear Post GIS Users

 

Is there a way in PostGIS of applying a formula to more than two Raster layers?

 

For example, I want to derive a new Raster Layer calculated as follows:

 

Constant1 x Layer1 x (Layer2 ^ Constant2) + Constant3 x Layer3 x (Layer4 ^ Constant4) + Constant5 x Layer5 x (Layer6 ^ Constant6)

 

Where  Constant1, Constant2, Constant3, Constant4, Constant5 & Constant6 are fixed constants.

                Layer1, Layer2, Layer3, Layer4, Layer5 & Layer6 are already derived Raster Layers.

                The ‘^’ sign represents raised to the power of. (i.e. 3^2 = 9).

 

How would I apply such a formula in PostGIS?

 

Kind Regards

 

David Westcott

 


Please consider the environment before printing this email. RSA are proud to be a responsible business - www.rsagroup.com/corporate-responsibility

*********************************************************************************************************************************************************************************
Royal & Sun Alliance Insurance plc (No. 93792). Registered in England & Wales at St. Mark's Court, Chart Way, Horsham, West Sussex, RH12 1XL.

Authorised by the Prudential Regulation Authority and regulated by the Financial Conduct Authority and the Prudential Regulation Authority.
For your protection, telephone calls may be recorded and monitored.
The information in this e-mail is confidential and may be read, copied or used only by the intended recipients. If you have received it in error please contact the
sender immediately by returning the e-mail. Please delete the e-mail and do not disclose any of its contents to anyone.
No responsibility is accepted for loss or damage arising from viruses or changes made to this message after it was sent.
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