Pansharpening in QGIS Using QTB

Posted: January 31, 2015 in GIS
Tags: , , , ,
UPD: you may also want to check out my post on Pansharpening Using R.
For a long time I wanted to play with the OrfeoToolBox instruments (and its GUI named Monteverdi) – a set of powerfull tools to process remote-sensing imagery. Finally I got the opportunity – I needed to perform pansharpening of the World-View-2 scene and I decided to make it using OTB modules available via QGIS Processing toolbox.
To make OTB modules available in QGIS you need to install it on your system. Official site provides good instructions on how to do it. When you have OTB installed you need to enable it in QGIS. Go Processing -> Options and configuration -> Providers, activate OTB and provide folder information if needed:

A dialogue to enable OTB modules in QGIS

Pansharpening is made in two steps: 1) resampling of the low resolution raster via Superimpose sensor tool; 2) pansharpening using Pansharpening tool. Alternatively you can do it using one command line (no QGIS or other GUI needed) in your OS’s console:
otbcli_BundleToPerfectSensor -inp pan_image -inxs xs_image -out output_image.
Performing two steps instead of just one is super-boring! Lets create a model that will allow us to perform pansharpening in QGIS in one step (virtually). Go to Processing Toolbox -> Models -> Tools and start creating new model:

Processing toolbox location of 'Create new model tool'

In the model creation window fill the fields of the model name and group name. Then add two rasters as inputs and name them: High_resolution_panchrom_raster and Low_resolution_raster. Now add the module named Superimpose sensor (Orfeo Toolbox -> Geomentry -> Superimpose sensor) and configure it to resample the Low_resolution raster: use High_resolution_panchrom_raster as input in Reference input field and Low_resolution_raster as input in The image to reproject field.

 

Superimpose sensor dialogue window

Add Pansharpening (rsc) (Orfeo Toolbox -> Geomentry -> Superimpose sensor) module to model. Use High_resolution_panchrom_raster as input in the Input PAN Image and output of the Superimpose sensor as the input in the Input XS Image field. Give a name (pansharpened_OTB) for the Output image to let model know that this is the final stage of the processing.

Pansharpening (rsc) dialogue window

Here how our model looks like in Model builder:

Overview of the Pan-sharpening model in model builder

And this is how it looks like when you launch it:

Pan-sharpening model window

Also you can skip model creation process and just download model that I created. You need to paste files from archive’s models folder into your /.qgis2/processing/models directory.
If you will have issues running OTB Pansharpening it is likely that they will be covered in following gis.stackexchange topics: OTB Pansharpening Error: Adapter for adaptPansharpening-bayes not found and What causes OTB pansharpening ERROR: Inputs do not occupy the same physical space?
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