The series of experimental studies to be described has been carried out in order to determine the feasibility of using corner reflectors as laboratory standards for model cross-section measurements.

Radar plays a major role in safety-critical applications mainly in the automotive industry due to its weather and lighting independence. The progress made in radar hardware technology has made it possible to detect objects more efficiently. Autonomous vehicles need to address a lot of problems encountered in their pathways which need proper detection and identification of obstacles for navigation purposes. Detection and identification of obstacles during navigation help in defining the trajectories for a vehicle so that collision can be avoided. A 77GHz radar system is used in many automotive industrial vehicles for automotive safety. At any given time, there is a possibility of multiple objects being in the vicinity of a vehicle that is not highly reflective which is based on its materialistic properties, such as prams or bicycles as compared to other road vehicles. In the work described in this thesis, we aim at designing, detecting, and identifying simple radar reflectors using copper sheets, which can be placed on such low reflective objects which helps in increasing pedestrian safety aspects. The software aspect of the radar module being used is achieved by using a demo application provided by the radar module manufacturer. This acts as the base structure for the python script which is used for detection and identification of the radar reflectors.

Kubhörnsreflektorer används som måltavlor med kontinuerlig och identifierbar reflekterad signalstyrka vid fjärranalys, bland annat för tekniken ”interferometric synthetic aperture radar” [InSAR]. Kubhörnsreflektorer tillämpas exempelvis för bevakning av sättningar i jordytan och kalibrering av [SAR]-system (”synthetic aperture radar”). Hur starkt en kubhörnsreflektor reflekterar satellitsignaler anges med ”radar cross section” [RCS], som minskar vid deformationer såsom avvikelse från ortogonalitet mellan reflektorplåtar, buktighet och ytoregelbundenheter. Därmed är det viktigt att kunna mäta och analysera sådana deformationer. Studiens syfte var att undersöka hur väl fotobaserad skanning [FBS] och terrester laserskanning [TLS] kan användas för att göra deformationsmätningar på kubhörnsreflektorer. En problematik med kubhörnsreflektorer är att ytorna vanligtvis är reflekterande och texturlösa.  Skanningen genomfördes i fältmiljö och FBS gjordes med en systemkamera. FBS-tekniken som användes i studien är baserad på Structure-from-Motion [SfM], vilket automatiserar bildmatchning och 3D-modellering. TLS utfördes med en Leica C10 på kort avstånd, cirka 2 m, från kubhörnsreflektorerna. Insamlade punktmoln segmenterades till separata punktmoln motsvarande de enskilda reflektorplåtarna och referensplan skapades för dessa. Referensplanen användes för att mäta vinklar mellan reflektorplåtar i alla punktmoln, med uppmätta avvikelser från ortogonalitet på 0–0,8°. Buktighet mättes som avstånd mellan plåtarnas punktmoln och referensplan och varierade mycket mellan de två reflektorernas sidor och mellan TLS och FBS, i ett spann från 0 till 6 mm. Ytoregelbundenheter i form av popnitar med storlek 0,6 mm kunde mätas i FBS-punktmoln. Mätosäkerheten var generellt något lägre för deformationsmätningar utifrån TLS jämfört med FBS i studien. Både TLS och FBS har begränsningar vid skanning av kubhörnsreflektorer på grund av reflektorernas ytegenskaper. För FBS kan dessa problem minskas med åtgärder i fält, såsom extra fokuspunkter och artificiell yttextur. TLS-resultat påverkades av infallsvinkeln mot reflektorplåtarna vid skanningen, eftersom en stor infallsvinkel leder till få returer och för liten infallsvinkel riskerar att leda till returer med hög intensitet (och felaktig position). Uppmätt deformation i studien skulle motsvara som mest en förlust på strax över en fjärdedel av det maximala RCS-värdet för den studerade reflektortypen. Den största RCS-förlusten i den här studien berodde på uppmätt buktighet i bottenplåten, i kontrast med att RCS-värdet enligt tidigare studier anses mer känsligt för avvikelse från ortogonalitet mellan reflektorplåtar. / Corner reflectors are used as targets with a continuous and identifiable reflected signal in remote sensing, commonly used with interferometric synthetic aperture radar [InSAR]. Corner reflectors are applied for monitoring crustal changes and calibrating synthetic aperture radar [SAR]-systems. The strength of the reflected radar signal is measured with radar cross section [RCS]. The RCS decreases if the reflector has deformations, such as deviation from orthogonality of the reflector plates, the plate curvature and surface irregularities. Therefore, it is important to be able to measure and analyse these kinds of deformations. The aim of this study was to examine how well close-range photogrammetry [CRP] and terrestrial laser scanning [TLS] can be used to measure deformations of corner reflectors. A problematic aspect of corner reflectors are their surfaces, that usually are reflective and textureless.  Scanning was conducted in a field environment and CRP was performed with a digital camera. The CRP-technique used in this study is based on Structure-from-Motion [SfM], which automates the image matching and 3D-modeling. TLS was done with a Leica C10 at short range from the corner reflector, about 2 m. The point clouds were segmented into separate point clouds for each reflector plate and reference planes were fitted to them. The reference planes were used to measure angles between reflector plates, with measured deviations from orthogonality between 0-0,8°. Plate curvature was measured as the distance from the point cloud to the reference plane and varied between the reflector sides and between TLS and CRP, in an interval from 0 to 6 mm. Surface irregularities in the shape of pop rivets, 0,6 mm in size, could be measured in the CRP-point clouds. Measurement uncertainties were generally lower in measurements based on TLS compared to CRP. Both TLS and CRP have limitations when scanning corner reflectors, caused by surface properties of the corner reflector. These problems can be reduced for CRP with certain field measures, such as extra focus points and artificial surface texture. The TLS results were affected by the incident angle while scanning, since a large incident angle leads to few return pulses and a too small incident angle may lead to returns with high intensity (and incorrect position). Measured deformation in this study would be equivalent to a reduction of RCS slightly above one fourth of the maximum RCS-value for the studied corner reflector type. In contrast to earlier studies, which say that RCS is most sensitive to lack of orthogonality between the plates, the largest reduction of RCS in this study was caused by the measured plate curvature of the bottom plate.