Fast and accurate point surveying using the PIX4Dcatch mobile app

Abstract. The digitalization of the architecture, construction and subsurface utility engineering sectors demands efficient, accurate and flexible 3D point surveying methods. Established ones based on Global Navigation Satellite System (GNSS) rovers or total stations suffer from significant limitations, such as requiring open-sky visibility, high costs and complex setups. This paper introduces a novel method for georeferencing 3D points using the PIX4Dcatch mobile application coupled with an external Real-Time Kinematic (RTK) GNSS receiver. The method enables to survey a point of interest by just aiming the smartphone and tapping on the screen during a capture. A lightweight, modified Bundle Adjustment algorithm runs on the device, delivering accurate 3D coordinates in seconds without any post-processing. We evaluated the method by surveying several known cadaster points for hundreds of times across diverse field conditions, achieving a mean planimetry error norm of approximately 3 cm and 97% of errors below 10 cm. Similar statistics are achieved with single-point measurements using an RTK rover. Although not intended to replace millimeter-precision instruments, the accuracy profile of our method is perfectly suited for many applications, such as subsurface utility mapping, which often have decimeter-level regulatory requirements. Given its high efficiency, low cost and ease of use, we believe that our method has the potential to transform as-built documentation workflows in diverse engineering sectors.