The processing procedure of merging RGB and thermal images described in this article, allows to use the higher resolution RGB images to compute a detailed 3D model, and to project the thermal texture on top of it: it uses RGB images to create the Point Cloud, then the Mesh Geometry will be created from this RGB point cloud and the texturing will be done using the thermal imagery. In order to perform this merging, both datasets indeed require geolocation.
However, please note that the data used for Point Cloud generation and thus DSM and Orthomosaic production are the RGB images. Therefore the obtained orthomosaic will be calculated from RGB images.
Moreover, please note that in a classic thermal project it is not recommended to use the orthomosaic outputs from thermal imageries, they are color balanced, do not represent the true pixel value and can generate artifacts. We instead advise users to use the Index Calculator in a separate project in order to visualize thermal maps, more information here.