Pansharpening in QGIS Using QTB

UPD: also you may 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:

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:

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. 

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.

Here how our model looks like in Model builder:

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

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? 

Unifying Extent and Resolution of Rasters Using Processing Framework in QGIS

My post about modification of extent and resolution of rasters drew quite a bit of attention and I decided to make a small New Year's present to the community and create a QGIS Processing script to automate the process.

The script was designed to be used within Processing module of QGIS. This script will make two or more rasters of your choice to have the same spatial extent and pixel resolution so you will be able to use them simultaneously in raster calculator. No interpolation will be made - new pixels will get predefined value. Here is a simple illustration of what it does:

Modifications to rasters A and B

To use my humble gift simply download this archive and unpack files from 'scripts' folder to your .../.qgis2/processing/scripts folder (or whatever folder you configured in Processing settings). At the next start of QGIS you will find a 'Unify extent and resolution' script in 'Processing Toolbox' in 'Scripts' under 'Raster processing' category:

If you launch it you will see this dialogue:

Main window

Note that 'Help' is available:

Help tab

Lets describe parameters. 'rasters' are rasters that you want to unify. They must have the same CRS. Note that both output rasters will have the same pixel resolution as the first raster in the input.

Raster selection window

'replace No Data values with' will provide value to pixels that will be added to rasters and replace original No Data values with the value provided here. Note that in output rasters this value will not be saved as No Data value, but as a regular one. This is done to ease feature calculations that would include both of this rasters, but I'm open to suggestions and if you think that No Data attribute should be assigned I can add corresponding functionality.

Finally you mast provide a path to the folder where the output rasters will be stored in 'output directory' field. A '_unified' postfix will be added to the derived rasters file names: 'raster_1.tif' -> 'raster_1_unified.tif'

If CRSs of rasters won't match each other (and you will bypass built-in check) or  an invalid pass will be provided a warning message will pop up and the execution will be cancelled:

Example of the warning message

When the execution is finished you will be notified and asked if rasters should be added to TOC:

Happy New Year!

P.S. I would like to thank Australian government for making the code they create an open source. Their kindness saved me a couple of hours.