On September 9, 2012, SPOT 6 was launched adding to the constellation of Earth- imaging satellites designed to provide 1.5m high-resolution data. The architecture of SPOT 6 is similar to that of the Pleiades satellites, both orbiting at an altitude of 694km. SPOT 6 has an imaging swath of 60kms and is suited for mapping, surveillance and monitoring.
The following is a brief tutorial showing a step by step procedure for pansharpening and orthorectifying SPOT 6 imagery using Geomatica OrthoEngine 2013.
Initial Project Setup
1. Open the Geomatica 2013 OrthoEngine application
2. In OrthoEngine
a) Click File > New
3. Give your project a Filename, Name and Description
a) Select Optical Satellite Modeling as the Math Modeling Method.
b) Select Rational Function (Extract from image) under Options. The Rational Function Method (RFM) has been the most popular geometric correction method in orthorectifying high resolution images. This method uses the RPCs provided with the satellite data to perform orthorectification. At this point Toutin’s Model can also be selected. If you are manually collecting GCP’s using Toutin’s Model, a minimum of 6 GCP’s are required.
c) Click OK
4. Input the appropriate Output projection and GCP projection information for your project
It is always preferable to perform the pan-sharpening process before geometric correction if a pan-sharpened orthorectified image is desired. This method works for most areas with gentle terrain. Performing pan-sharpening after geometric correction often results in small misalignments between the ortho data due to the accuracy of GCPs and DEMs used in the orthorectification process.
5. Click on Utilities > Merge/Pansharp Multispectral Image…
6. Select the Multispectral image in the dataset. Select the DIM_SPOT6_.xml file
a) Select the Panchromatic image. Select the DIM_SPOT6_.xml file
b) Select the output filename and location for the output PIX file
c) Click Pansharp
d) When the pansharp process is complete click Yes when asked to add the scene into the project
About the output
PCI’s Geomatica award winning pansharpening algorithm (Co-developed with UNB) is capable of taking a multispectral image and its coincident/co-registered panchromatic pair and produce outstanding pansharpened results. The output is a beautifully sharp high resolution multispectral image with the resolution of the panchromatic image. The pansharpened process takes a high resolution panchromatic image and a lower resolution multispectral image and produces a high resolution multispectral image (same resolution of panchromatic image) with very sharp edges.
SPOT6 PCI pan-sharpened image (above)
In order to leverage the SPOT 6 images for applications such as GIS, it is necessary to orthorectify the images. A geometric model, ground control points (GCPs) and a digital elevation model (DEM) is required.
7. Select Data Input as the Processing step
a) Click Open a new or existing image
b) Click New Image
c) Navigate to the location of the data. Select the DIM_SPOT6_.xml file if you wish to use the raw imagery. If you pansharpend the imagery as shown in the steps above, the pansharpened PIX file will already be added to the project. Skip to step 8.
d) Select Yes when asked if you want to import the data file to a PIX file for optimized processing
e) Select a file name and location for your output PIX file
f) Select Yes when asked if you want to create overviews now
8. In the OrthoEngine toolbar select GCP/TP Collection as the Processing step
a) Select Collect GCP’s Manually
Note: GCP’s can be collected automatically using collect GCP’s automatically from the GCP/TP Collection Processing step. Automatic tie point collection can also be used without collecting any GCPs.
b) Collect GCP’s for the project using manual entry, from geocoded images, vectors, chip databases, digitizing tablet or a text file.
9. In the OrthoEngine toolbar select Ortho Generation as the Processing step
a) Click Schedule ortho generation
b) Move the Available images to the Images to process window
c) Select an output file name and location for the ortho image
d) Select a DEM file
e) Select a Sampling interval
f) Change the Resampling method to Cubic
g) Click Generate Orthos
10. To view the completed ortho select File > Image View… on the OrthoEngine Toolbar