Abstract
Nowadays, Unmanned Aerial Vehicle (UAV) on-board photogrammetry knows a significant growth due to the democratization of using drones in the civilian sector. Also, due to changes in regulations laws governing the rules of inclusion of a UAV in the airspace which become suitable for the development of professional activities. Fields of application of photogrammetry are diverse, for instance: architecture, geology, archaeology, mapping, industrial metrology, etc. Our research concerns the latter area. <i>Vinci-Construction- Terrassement</i> is a private company specialized in public earthworks that uses UAVs for metrology applications. This article deals with maximum accuracy one can achieve with a coupled camera and GPS receiver system for direct-georeferencing of Digital Surface Models (DSMs) without relying on Ground Control Points (GCPs) measurements. This article focuses specially on the lever-arm calibration part. This proposed calibration method is based on two steps: a first step involves the proper calibration for each sensor, i.e. to determine the position of the optical center of the camera and the GPS antenna phase center in a local coordinate system relative to the sensor. A second step concerns a 3<i>d</i> modeling of the UAV with embedded sensors through a photogrammetric acquisition. Processing this acquisition allows to determine the value of the lever-arm offset without using GCPs.
Highlights
In the context of direct-georeferencing of Unmanned Aerial Vehicle (UAV) aerial images using an on-board GPS receiver, lever-arm calibration is an important step in the data processing pipeline to ensure maximum accuracy when generating a Digital Surface Models (DSMs)
Each acquisition provides a lever-arm value with respect to the second calibration methodology 3.2 and allows us at least to control the mechanical stability between the start of the acquisition and its end
Before comparing the values of the lever-arm vector provided by this method and the one obtained by classical in-flight selfcalibration method based on Ground Control Points (GCPs) 3.1, we can compare the calculated values before the UAV take-off and after the UAV landing
Summary
In the context of direct-georeferencing of UAV aerial images using an on-board GPS receiver, lever-arm calibration is an important step in the data processing pipeline to ensure maximum accuracy when generating a DSM. We rely on processing carrier-phase raw embedded GPS data to get the camera position while the photogrammetric image processing based on tie points extraction (Lowe, 2004) provides the camera orientation. The conventional method to calibrate this vector is generally based on external measurements as well as the mechanical stability of the mounting of the sensors on the UAV is required. We propose in the following a study of the impact of leverarm determination on direct-georeferencing accuracy and a different calibration method requiring only photogrammetric measurements without any special mechanical sensors mounting configuration constraint
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
