Douterloigne, Koen

Gautama, Sidharta

Philips, Wilfried

English

Ghent University Academic Bibliography

Evaluating and improving the accuracy of 3Dmodels from UAS imageryKoen DouterloigneSupervisor(s): Sidharta Gautama, Wilfried PhilipsI. INTRODUCTIONAerial images taken by an Unmanned Air-craft System (UAS) are used to generate largegeoreferenced overviews of a terrain. In ad-dition, structure from motion algorithms haveenabled the creation of three dimensional (3D)digital terrain models of this terrain [1]. As ap-plications using these 3D models become moredemanding, the accuracy requirements grow. Inour work we evaluate the real world accuracy ofstate of the art 3D reconstruction methods andpropose a system to improve the results.II. MEASURING THE ACCURACYAfter creating a 3D model using the methodsfrom [1] and [2] we measure the correctness ofthe resulting 3D points by comparing them withground truth. This ground truth is acquired byplacing cross shaped markers on the terrain andmeasuring their position using surveyor equip-ment. Evaluating the model like this we ob-tain an error of up to 5 meter in all directions,mainly caused by the low quality GPS onboardthe UAS.III. IMPROVING THE ACCURACYWe improve the global accuracy by includ-ing some of the ground truth into the compu-tations. Our experiments show that a very lim-—————————————————–We like to acknowledge the support under theSTEREO II programme of the Belgian Science Pol-icy. The research has been performed as part ofthe RIMS project ”Reliable Image Management Sys-tems” in cooperation with VITO (Flemish Institutefor Technological Research) and IncGEO (Incubatorfor Geoinformation).ited amount of points suffices to achieve muchbetter results. This is shown in figure 1, wheremarkers 4, 7, 12 and 14 were used as groundtruth. The computed position of the other mark-ers is now within 20 centimeter of their actualposition. This is close to the error produced bythe surveyor equipment, of about 10 cm.-0.5-0.4-0.3-0.2-0.100.10.20.30.40.52 3 4 5 6 7 8 9 10 11 12 13 14 15∆x∆y∆zFigure 1. The difference in meter between measuredand computed marker positions.IV. CONCLUSIONSWe have shown that by including a limitedamount of ground control points in the 3D re-construction of a terrain, an accuracy of 10 to20 cm in all directions can be achieved. Thisimplies that ground based surveying is still re-quired, but only at a fraction of the time andcost when no UAS would be used.REFERENCES[1] M.I.A. Lourakis and A.A. Argyros, “SBA: ASoftware Package for Generic Sparse Bundle Ad-justment,” ACM Trans. Math. Software, vol. 36,no. 1, pp. 1–30, 2009.[2] Y. Furukawa and J. Ponce, “Accurate, Dense, andRobust Multiview Stereopsis,” IEEE Trans. Pat-tern Anal. Mach. Intell., vol. 32, no. 8, pp. 1362–1376, 2010.

Evaluating and improving the accuracy of 3D models from UAS imagery

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Evaluating and improving the accuracy of 3D models from UAS imagery

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Ghent University Academic Bibliography