6X - How to Process Data from 6X in Metashape

6X - How to Process Data from 6X in Metashape

Note: This stitching process can be used for all variants of the 6X, including the 6X Thermal.

When using a reflectance panel, raw images should first be run through the radiometric corrections script
Corrections Script Instructions 

The following steps describe how to process data from Sentera 6X multispectral sensor. Described here are the main steps and the general recommendations for processing in   Agisoft Metashape Professional .

Add Photos

1.      To add photos, select Add Folder from the Workflow menu.

2.      Select the folder containing the individual band folders. The images are grouped into folders of the corresponding channel.

Note:

  •  Photos must be added as a multi-camera system to produce a multispectral mosaic.
  •  The number of images per band folder must be the same. Otherwise, all of the bands will not be added to the chunk.

Note: Sentera recommends processing RGB images separately, without using them in the multicamera method.

Camera Calibration Settings

Photogrammetric calibration of cameras is performed to determine the values of the interior orientation of the cameras, including the parameters of distortion of the camera lens.

1.      To open the Camera Calibration dialog window, select Tools > Camera Calibration.

2.      By default, NIR is selected as the master band. The NIR images have the highest chance of becoming oversaturated in poor lighting conditions without a sun sensor, so change the master band to Green by right-clicking the green band and clicking Set as Master.


3.      By default, the layer index for each band is set to NIR: 0, Blue: 1, Green: 2, Red: 3, RedEdge: 4. Set the layer index accordingly. This can be chosen differently by the user since some users may rather have the bands ordered Blue, Green, Red, RedEdge, NIR. Open the Bands tab on the Camera Calibration dialog window and specify Layer Index to change layer order.


4.      Metashape can perform automatic calibration during the align photos step. If very precise calibration data is available, click Select next to the Fixed Parameters: Item.

5.      In the Fixed parameters dialog box, choose the calibration parameters that are to be fixed and click OK. The initial values for the chosen parameters will not be changed during the Align Photos or Optimize Cameras operations.


Align Photos

Align photos and model/mesh generation is the same as the process for any other sensor and can be changed by the user depending on their needs.

1.      Select Align Photos from the Workflow menu.


Note: It is advisable to use the Reference Preselection - Source if there are coordinates of the photographing centers.

The result of the align photos operation will be shown in the Model View as the estimated camera locations and tie point cloud, representing the matching points between the images.


Build DEM

A DEM represents a surface model as a regular grid of height values. DEM can be rasterized from a dense point cloud, a sparse point cloud, depth maps, or a mesh. It is possible to build a Dense cloud before starting build DEM.

Note:

  • To build a dense point cloud (if performing terrain classification later), first build a cloud with the following parameters: Medium quality, Mild filtering. Then use the classified point cloud to build a DEM.
  • DEM is calculated for the part of the model within the bounding box.

1.      Select Build DEM from the Workflow menu.

2.      In the Build DEM dialog box, set parameters.


1.      Click OK. The progress dialog box will appear displaying the current processing status. To cancel the processing, click Cancel.



Orthomosaic Generation

1.      Select Build Orthomosaic from the Workflow menu.

2.      Set parameters in the Orthomosaic dialog box.


3.      Click OK. The progress dialog box will appear displaying the current processing status. To cancel the processing, click Cancel.


Note: Metashape enables the calculation of NDVI and other vegetation indices based on the multispectral imagery input. The vegetation index formula can be set by the user, thus allowing for great flexibility in data analysis. Use the Set Raster Transform option from the Tools menu to open Raster Calculator dialog box. From the Transform tab, specify the index values t to calculate from the source data.




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