... | ... | @@ -74,12 +74,13 @@ Two methods are available to define the parameters for calculating the displacem |
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![image62](uploads/57544052faaab716bf75176190b35f78/image62.png)
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- The **_size of the interrogation area_** (IA for Interrogation Area), in meters or pixels (linked units), see the page on [Principles of velocity measurement](#principes) for more details.
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- The **_size of the interrogation area_** (IA for Interrogation Area), in meters or pixels (linked units).
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> :warning: This area should be large enough to encompass tracers but small enough to represent the flow (velocity gradients in an IA should be negligible). As good practice, the IA size should match the tracer size and the characteristic scale of the measured flow, while remaining small enough to allow for reasonable calculation time. A size of about 30-50 pixels is recommended (the size must be an even number).
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The **_Apply_** button allows for a graphical visualization of the IA size on an orthorectified image. The user can choose the center position of the window by entering its coordinates in **_Center Position_** or by clicking on a pixel in the image after activating the **_Position_** button.
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- The size of the search area (SA for Searching Area) in meters or pixels (linked units), see the page on [Principles of velocity measurement](#principes) for more details.
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- The size of the search area (SA for Searching Area) in meters or pixels (linked units)
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> :thumbsup: The search area is a rectangle defined around the center of the interrogation area. It corresponds to the zone where patterns are searched for on successive images. When the flow has a preferred direction, the search area can be elongated in that direction.
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The SA is defined by 4 parameters: Sim, Sip, Sjm, and Sjp. The **_Apply_** button provides a graphical visualization of the SA size on an orthorectified image.
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... | ... | @@ -96,7 +97,7 @@ The SA is defined by 4 parameters: Sim, Sip, Sjm, and Sjp. The **_Apply_** butto |
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# :round_pushpin: Calculation Grid
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The calculation grid represents all the points for which a velocity will be calculated. For more details, see the [Principles of velocity measurement](#principes) page. Two methods are available for defining the calculation grid:
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The calculation grid represents all the points for which a velocity will be calculated. Two methods are available for defining the calculation grid:
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- The **_Analyse LSPIV_** 🡪 **_Grid Points 🡪 Define_** menu opens the interface for defining the **_Grid Contour_** for tracer displacements.
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- The grid contour is a quadrilateral defined by its four corners through clicks on the orthoimage.
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... | ... | @@ -113,7 +114,7 @@ The calculation grid is stored in the **_outputs.dir\\grid.dat_** file, and the |
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# :stopwatch: Tracer Displacement Computation
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The **_Analyse LSPIV🡪 Calculate Instantaneous Results_** menu starts the statistical analysis of tracer displacements for all image pairs in the sequence. For more details, see the [Principles of velocity measurement](#principes) page.
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The **_Analyse LSPIV🡪 Calculate Instantaneous Results_** menu starts the statistical analysis of tracer displacements for all image pairs in the sequence.
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An "instantaneous" velocity field (at the time interval between two images) is obtained for all consecutive image pairs. Thus, for N selected images, N-1 velocity fields are obtained, stored in the **_vel_raw_** folder.
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... | ... | @@ -121,7 +122,7 @@ The **_Raw Results (B)_** layer group is created. |
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![image68](uploads/7bf272478da0fd36ef09786e820a0067/image68.png)
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It allows visualizing the velocities calculated for image pairs in the form of a vector field (**_Velocities B_**), streamlines (**_Particles B_**, [see how to calculate them here](#_Calcul_des_lignes)), or contour plots (**_Isosurfaces B_**). More details on [visualizing and configuring velocity layers here](#r%C3%A9f%C3%A9rences-bibliographiques). The graphical interface allows linking the visualization of images and calculated velocities via the **_Link/Unlink Images and Velocities_** button.
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It allows visualizing the velocities calculated for image pairs in the form of a vector field (**_Velocities B_**), streamlines (**_Particles B_**), or contour plots (**_Isosurfaces B_**). More details on [visualizing and configuring velocity layers here](#r%C3%A9f%C3%A9rences-bibliographiques). The graphical interface allows linking the visualization of images and calculated velocities via the **_Link/Unlink Images and Velocities_** button.
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![image69](uploads/e35652b2f4fc8d57e9a200320b09d1e1/image69.png)
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