Merging and pansharpening multispectral channels

In the Merge/Pansharp Multispectral Images window, you can do the following:

Merge separate multispectral images files into a single file.
Pansharpen images by using multispectral and panchromatic files.

Typically, panchromatic (PAN) and multispectral (MS) images are processed separately before pansharpening to ensure that both data sets are aligned with each other. These image-processing steps include reading the data, collecting the ground control points (GCP) and orthorectifying the data with a digital elevation model (DEM). If the image-processing steps are performed separately on each image type, a misalignment may occur between the PAN and MS images because of the location and distribution of the GCPs.

With many data products, such as Worldview/Quickbird Ortho-Ready Standard data, SPOT, and Pleaiades, the PAN and MS images are resampled exactly on top of each other. Therefore, it is possible to perform pansharpening of the data, first for gentle terrain, before further processing. You need only perform GCP collection and orthorectification once on the pansharpened image. For data which has small misalignment between the PAN and MS images, it is possible to use Adjustment before pansharpening option before pansharpening to correct the misalignment.

Many high-resolution satellite data products, such as IKONOS and QuickBird, are distributed in one rapid positioning capability (RPC) file, and the four channels (blue, green, red, and NIR) in separate files.

Instead of importing and correcting these files separately in OrthoEngine, you can use Merge/Pansharp Multispectral Image to merge separate MS images into one file, or perform pansharpening by using the PAN and MS image files. The resulting file automatically imports the RPC, and can then be added to your project.

Note: The RPC file is a text file that provides the coefficients to define the rational functions math model for the scene.

To merge and pansharpen multispectral channels

In OrthoEngine, start an Optical Satellite Modeling project with the option Rational Function (Extract from image).
In the OrthoEngine window, on the Tools menu, click Merge/Pansharp Multispectral Image.
The Merge/Pansharp Multispectral Images window appears.
In the Multispectral image 1 through Multispectral image 4 boxes, as applicable, type the path and file name of each image or, to select a file, click Browse.
The order of the boxes determines the channel order in the output file. That is, the file entered in Multispectral image 1 becomes channel 1 in the output. If the MS data is distributed in a single file, you need only specify the file name in the Multispectral image 1 box.
To perform pansharpening, in the Panchromatic image box, type the path and file name of the PAN image or, to select a folder, click Browse.
In the Output filename box, type the path and file name for your merged/pansharpened file or, to select a folder, click Browse.
Do one of the following, as applicable:
- To pansharpen the files:
  1. To refine the output imagery, select the Enhanced pansharpening check box.
  2. Some multispectral and panchromatic images have small misalignment between each other. To correct the misalignment before pansharpening, select the Alignment before pansharpening check box. The user can choose either polynomial or supermatch method to correct the misalignment.
  3. In the Resampling list, click the resampling method to use to determine the output pixel values: Cubic or Bilinear.
    Tip: If you intend to use the output to perform additional analysis, such as classification, select Bilinear. Doing so keeps the output values closer to the original MS pixel values.
  4. click Pansharp
  A progress window appears, indicating the pansharpening of the data and creation of the output file.
- To merge MS files, click Merge.
  A single multichannel file is created and the RPC file is imported automatically.