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Spatial accuracy of UAV- derived orthoimagery and topography: Comparing photogrammetric models processed with direct geo-referencing and ground control points / Chris H. Hugenholtz in Geomatica, vol 70 n° 1 (March 2016)  

Public [article]  inGeomatica > vol 70 n° 1 (March 2016) . - pp 21 - 30 Titre : Spatial accuracy of UAV- derived orthoimagery and topography: Comparing photogrammetric models processed with direct geo-referencing and ground control points Type de document : Article/Communication Auteurs : Chris H. Hugenholtz, Auteur ; Owen Brown, Auteur ; Jordan Walker, Auteur ; et al., Auteur Année de publication : 2016 Article en page(s) : pp 21 - 30 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications photogrammétriques [Termes IGN] acquisition de données [Termes IGN] analyse comparative [Termes IGN] capteur aérien [Termes IGN] drone [Termes IGN] géoréférencement direct [Termes IGN] point d'appui [Termes IGN] positionnement cinématique en temps réel [Termes IGN] positionnement inertiel [Termes IGN] positionnement par GNSS [Termes IGN] positionnement par GPS [Termes IGN] qualité des données [Termes IGN] réalité de terrain [Termes IGN] topographie Résumé : (auteur) Mapping with unmanned aerial vehicles (UAVs) typically involves the deployment of ground control points (GCPs) to georeference the images and topographic model. An alternative approach is direct georeferencing, whereby the onboard Global Navigation Satellite System (GNSS) and inertial measurement unit are used without GCPs to locate and orient the data. This study compares the spatial accuracy of these approaches using two nearly identical UAVs. The onboard GNSS is the one difference between them, as one vehicle uses a survey-grade GNSS/RTK receiver (RTK UAV), while the other uses a lower-grade GPS receiver (non-RTK UAV). Field testing was performed at a gravel pit, with all ground measurements and aerial surveying completed on the same day. Three sets of orthoimages and DSMs were produced for comparing spatial accuracies: two sets were created by direct georeferencing images from the RTK UAV and non-RTK UAV and one set was created by using GCPs during the external orientation of the non-RTK UAV images. Spatial accuracy was determined from the horizontal (X,Y) and vertical (Z) residuals and root-mean-square-errors (RMSE) relative to 17 horizontal and 180 vertical check points measured with a GNSS/RTK base station and rover. For the two direct georeferencing datasets, the horizontal and vertical accuracy improved substantially with the survey-grade GNSS/RTK receiver onboard the RTK UAV, effectively reducing the RMSE values in X, Y and Z by 1 to 2 orders of magnitude compared to the lower grade GPS receiver onboard the non-RTK UAV. Importantly, the horizontal accuracy of the RTK UAV data processed via direct georeferencing was equivalent to the horizontal accuracy of the non-RTK UAV data processed with GCPs, but the vertical error of the DSM from the RTK UAV data was 2 to 3 times greater than the DSM from the non-RTK data with GCPs. Overall, results suggest that direct georeferencing with the RTK UAV can achieve horizontal accuracy comparable to that obtained with a network of GCPs, but for topographic measurements requiring the highest achievable accuracy, researchers and practitioners should use GCPs. Numéro de notice : A2016-433 Affiliation des auteurs : non IGN Thématique : IMAGERIE/POSITIONNEMENT Nature : Article DOI : 10.5623/cig2016-102 En ligne : https://doi.org/10.5623/cig2016-102 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=81330 [article]

Applying ASPRS accuracy standards to surveys from small unmanned aircraft systems (UAS) / Ken Whitehead in Photogrammetric Engineering & Remote Sensing, PERS, vol 81 n° 10 (October 2015)  

Public [article]  inPhotogrammetric Engineering & Remote Sensing, PERS > vol 81 n° 10 (October 2015) . - pp 787 - 793 Titre : Applying ASPRS accuracy standards to surveys from small unmanned aircraft systems (UAS) Type de document : Article/Communication Auteurs : Ken Whitehead, Auteur ; Chris H. Hugenholtz, Auteur Année de publication : 2015 Article en page(s) : pp 787 - 793 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications photogrammétriques [Termes IGN] drone [Termes IGN] modèle numérique de surface [Termes IGN] norme de données localisées [Termes IGN] orthoimage [Termes IGN] point d'appui [Termes IGN] précision des données Résumé : (auteur) We present a first assessment of UAS-derived orthoimagery and digital elevation data in the context of newly-released accuracy standards for digital geospatial data developed by the American Society for Photogrammetry and Remote Sensing. We outline results from two case studies using a commercially-available UAS, photogrammetry software, and an array of ground control and check points. Radial horizontal and vertical root-meansquare- errors (RMSE) were calculated as 0.05 m and 0.06 m, respectively, for one site, and 0.08 m and 0.03 m, respectively, for the other. Under the 1990 ASPRS standards, both surveys meet the requirements for Class 1 accuracy at the 1:500 map scale and at the 0.50 m contour interval. Under the newly-developed ASPRS standards, the reported errors fulfill the requirements for both horizontal and vertical mapping at the 10 cm RMSE level. Overall, these results provide initial direction for practitioners considering UAS surveying in the context of accuracy standards Numéro de notice : A2015-989 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article DOI : 10.14358/PERS.81.10.787 En ligne : https://doi.org/10.14358/PERS.81.10.787 Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=80270 [article]