Agisoft Metashape supports the processing of thermal images in TIFF format. When shooting thermal images, it is very important to maintain overlap between images, preferably 80-90% due to low image resolution. It is also important to specify the parameters for the sensor (focal length, pixel size) in the Camera calibration dialog window.

To obtain absolute temperature values, you should use images of a single-channel TIFF file in floating-point format, providing that it is possible to apply the single formula to all the images that will convert those floating-point values to the temperature values. 


The data from the following article - "UAV-based Multispectral & Thermal dataset for exploring the diurnal variability, radiometric & geometric accuracy for precision agriculture" was used as a dataset for the tutorial. 


Metashape supports processing of thermal data from AscTec (ARA format), WIRIS (TIFF format) cameras and cameras saving data in R-JPEG (FLIR data) format.

For other therma images if you are interested in temperature values extraction from the orthomosaic, you need to pre-process the images in the external application that will transform Radiometric JPEGs into single-band TIFF files with the floating-point values, where each value either represent temperature value directly or can be re-calculated to the temperature using analytical formula - same for all the images in the set.


Sections in the article:


To load thermal images


1. Add thermal images to the project using Add Folder... command from the Workflow menu. 


2. In the Add Folder dialog box browse to the parent folder containing subfolders with images. Then click Select Folder button. 


3. Click the OK button to close the dialog. EXIF GPS tags will be automatically loaded.



Align Photos


For thermal data, before starting the alignment process we recommend specifying the sensor parameters according to the camera/sensor specifications in the Camera Calibration dialog window. Select Camera Calibration command from the Tools menu:



After specifying the camera parameters, we recommend fixing the focal length in the Camera Calibration dialog:



The photo-alignment processing step includes feature point detection, image matching, aerial triangulation, and bungle adjustment procedures. 


1. Select Workflow > Align Photos.


2. Set the parameters in the Align Photos dialog window:




Due to the low quality of thermal images, we recommend using Accuracy - High or even Highest.

If images have coordinate data information loaded to the Reference pane, we recommend using the Reference preselection (Source option).


The results of this processing step comprise estimated external (camera position + orientation) and internal parameters and tie point cloud as a visualization of triangulation for matched feature points procedure. Results of the processing step displayed in the Model view:


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 tie point cloud, depth maps or a mesh. DEM is calculated for the part of the model within the bounding box. We used depth maps for building DEM.


1. Select the Build DEM... command from the Workflow menu.


2. In the Build DEM dialog box set parameters. 



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


Build Orthomosaic 


1. Select the Build Orthomosaic... command from the Workflow menu.


2. Set parameters in the Orthomosaic dialog window.  




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




If you are interested in temperature values extraction from the orthomosaic generated from R-JPEG not for FLIR based cameras, you need to pre-process the images in the external application that will transform Radiometric JPEGs into single-band TIFF files with the floating-point values, where each value either represent temperature value directly or can be re-calculated to the temperature using analytical formula - same for all the images in the set.


Raster calculator


To extract the absolute temperature values from the thermal orthomosaic it is necessary to define the formula that would transform raw values to the temperature values via Raster Calculator dialog window. Select Set Raster Transform command in the Tools menu. Add the formula in the Transform tab (formula may depend on the thermal device used):



To create the false color representation for thermal data:  


1. Select or create Palette for images in Raster Calculator dialog. 



2. Click Apply button. 


3. Click OK button to close the dialog. 


Then review the orthomosaic in False color representation.