Re: [postgis-users] 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 <
david.westc...@uk.rsagroup.com> 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
>
> 
> 
> *
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[postgis-users] 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


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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