... | ... | @@ -229,7 +229,7 @@ There are three methods for positioning reference points: |
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- Click on the pixel in the image to locate the Ground Reference Point (GRP); the image coordinates **_I_** and **_J_** will then be populated.
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> :thumbsup: You can zoom in for better visibility of a point. You can also delete or reorder reference points, as well as modify, copy, or paste the coordinates of reference points in the input table.
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Repeat this operation for all reference points (at least 4 for 2D orthorectification (ideal: 15-30 points); at least 6 for 3D orthorectification (ideal: 20-40 points); see [In-depth explanations](#principle-of-orthorectification) for more details).
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Repeat this operation for all reference points (at least 4 for 2D orthorectification (ideal: 15-30 points); at least 6 for 3D orthorectification (ideal: 20-40 points); see [In-depth Explanations of Principle of Orthorectification](#principle-of-orthorectification) for more details).
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The **_End Entry_** button finalizes the operation and creates a file in the project directory: **_outputs.dir\\GRP.dat_**.
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... | ... | @@ -258,7 +258,7 @@ The corresponding real-world coordinates (X and Y) are automatically calculated |
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## Verification of GRPs
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The **_Orthorectification 🡪 Orthorectification 🡪 Verify Reference Points_** menu allows you to check the quality of the match between terrain and image coordinates of the GRPs. The orthorectification matrix (see [Principles of Orthorectification](#approfondissements)) is calculated, and the terrain position (X; Y; Z) of the reference points is determined from their image coordinates (I and J).
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The **_Orthorectification 🡪 Orthorectification 🡪 Verify Reference Points_** menu allows you to check the quality of the match between terrain and image coordinates of the GRPs. The orthorectification matrix (see [In-depth explanations of Principles of Orthorectification](#principle-of-orthorectification)) is calculated, and the terrain position (X; Y; Z) of the reference points is determined from their image coordinates (I and J).
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Then, the real terrain coordinates are compared with the calculated terrain coordinates. The distance between these real and calculated coordinates, called **_Offsets_**, is shown in a table and as a graph.
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![image51](uploads/53e406f79b41496b15bd433cfcaf2cfb/image51.png)
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... | ... | @@ -278,7 +278,7 @@ There are two ways to set the transformation parameters: |
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The **_Orthorectification 🡪 Orthorectification 🡪 Transformation Parameters 🡪 Define_** menu opens the **_Transformation Parameters_** management window.
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- Define the study area with a rectangle, specifying the corner positions in the real-world coordinates (**_Xmin, Xmax, Ymin, Ymax_**). This frame limits orthorectification to the area of interest, thus reducing computation time.
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- **_Resolution_**, in meters per pixel, represents the size of one pixel in the orthorectified image. Adjust the resolution to keep tracer details visible in the orthoimage without producing excessively large orthoimages (the orthoimage should be about the same size as the raw image). The button ![image53](uploads/67c708dadea4320b35173c0f5155cc72/image53.png) automatically fills in the fields **_Xmin, Xmax, Ymin, Ymax, and Resolution._**
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- Finally, specify the **_Water Level_** in real-world coordinates. The orthoimage will only be valid at this level (see [the principles of orthoimage creation](#cr%C3%A9ation-des-orthoimages)).
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- Finally, specify the **_Water Level_** in real-world coordinates. The orthoimage will only be valid at this level (see [In-depth explanations of Principle of orthorectification](#principle-of-orthorectification)).
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Clicking **_Apply_** produces an orthorectified image. Adjust the parameters as needed, then **_Validate._** Transformation parameters are stored in the file **_outputs.dir\\img_ref.dat_**.
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