Ground penetrating radar was presumably used as LiDaR is for surface mapping, but the coloration would seemingly indicate LiDaR was used in conjunction with GPR, as described here. I'm just speculating bit it seems apparent to me that both technologies were used in unison as the 3D mapping is specific to LiDaR.
"GPR allows for a fast and non-invasive surveying of structures and anomalies of the sub surface, by using electromagnetic radiation in the microwave range. The active remote sensing technique LiDAR (Light Detection and Ranging, also known as Laser Scanning), measures the runtime of discrete light pulses in order to map objects and structures on the surface of the earth... A standard GPR-processing-workflow does not allow for a 3-dimensional visualisation of the results and complicates the detection of archaeological structures. Unlike, LiDAR which does allow for a 3-dimensional visualisation. A fusion of both techniques, by using Python scripts and the software packages REFLEXW - Sandmeier Scientific Software and LASTools - rapidlasso, applies the advantages and specialities of LiDAR and GPR, and allows to get a high-resolution 3-dimensional pointcloud."
A Fusion of GPR- and LiDAR-Data for Surveying and Visualisation of Archaeological Structures - a case example of an archaeological site in Strettweg, District of Murtal, Austria - NASA/ADS