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Radar Orthorectification Workflow

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The following tutorial demonstrates how to use OrthoEngine to orthorectify Radar data. Note that only certain levels of Radar satellite data can be orthorectified. The Radar Ortho Suite technical specification document lists the supported radar sensors for orthorectification: http://www.pcigeomatics.com/pdf/geomatica/techspecs/2018/Radar-Ortho-Suite.pdf.

Project Setup

Imagery Import

GCP/TP Collection (Optional)

Ortho Production

View Product (Optional)

Project Setup

  1. Open Geomatica OrthoEngine

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  1. From the OrthoEngine toolbar, click File > New
  2. Give your project a Filename, Name, and Description.
  3. Select Radar Satellite Modelling as the Math Modelling Method
  4. Select the appropriate modelling method under Information on each of the model options is listed below and additional information is available from the Geomatica Help: http://www.pcigeomatics.com/geomatica-help/concepts/orthoengine_c/MathModels_Radar_explain.html
    • Toutin’s Model is a rigorous model that compensates for known distortions to calculate the position and orientation of the sensor at the time of image acquisition. It is suitable for use with any optical satellite data, regardless of resolution, such as CARTOSAT, LANDSAT, or SPOT.
    • Radar Specific Model uses the additional parameters in the orbit data to diminish the number of ground control points (GCP) required. The extra parameters maintain the positional accuracy and high levels of detail in the model, but the number of GCPs needed is reduced to few or none. This math model does not use tie points because each scene is computed using the GCPs of that scene only. This model is for use specifically with SAR data, such as ASAR, ALOS PALSAR, COSMO-SKYMED, RADARSAT, and TerraSAR-X/TanDEM-X.
    • Rational Function can be applied to any image data set. If RPCs are unavailable, they can be generated from the points stored in the GCP segment (see RFMODEL). The advantage of using Rational Function (Extract from image) is that you can apply it to images that have been modified, do not contain an orbit segment, or both. This math model is recommended for use with data sets in map orientation, image subsets, or those with no orbital information.

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  1. In the Set Projection window, click
    • While this information can be entered manually, cancelling will ensure that projection information will be read from the first loaded image.

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  1. Click OK

Imagery Import

  1. In the OrthoEngine toolbar, select Ortho Generation as the Processing step
  2. Click Open an image

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  1. From the File Selector window, click Add Image…
  2. Navigate to and select the key file of your sensor
    • The key file depends on the sensor you are using. You can find this information in the Geomatica Help. You can search the help for the sensor that you are using and the Key file name will be listed in the first table (see example below).

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  1. Choose a Calibration Type

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  1. When prompted, choose No to importing to a pix and No to creating overviews
  2. Click Close

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GCP/TP Collection (Optional)

Optionally, you can collect ground control and tie points as per the following tutorial:

https://support.pcigeomatics.com/hc/en-us/articles/209885893-Satellite-Orthorectification-Workflow.

The following section of the Geomatica Help outlines the minimum number of GCPs to collect for each type of OrthoEngine math model: https://www.pcigeomatics.com/geomatica-help/concepts/orthoengine_c/Chapter_55.html. In this example the rational functions (extract from image) is used and as such does not specifically require GCPs to be collected.

Ortho Production

  1. From the OrthoEngine toolbar, select Schedule Ortho Generation

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  1. In the Ortho Image Production window:
    • Select your image in the Available images box and click the arrow to move it to the Images to process box
    • Set a File name for your result in the Ortho Image section
    • Select your DEM in the Ortho Generation Options. This tutorial makes use of “gmted2010.pix” which can be found in the Geomatica installation directory: C:\PCI Geomatics\Geomatica 201X\etc
    • Click OK

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  1. Click Generate Orthos

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View Product (Optional)

You can optionally open and view the final orthorectified radar image in Focus.

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