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Using UAVs for map creation and updating: A case study in Rwanda / Mila Koeva in Survey review, vol 50 n° 361 (July 2018)  

Public [article]  inSurvey review > vol 50 n° 361 (July 2018) . - pp 312 - 325 Titre : Using UAVs for map creation and updating: A case study in Rwanda Type de document : Article/Communication Auteurs : Mila Koeva, Auteur ; M. Muneza, Auteur ; Caroline M. Gevaert, Auteur ; Markus Gerke, Auteur ; Francesco Nex, Auteur Année de publication : 2018 Article en page(s) : pp 312 - 325 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Photogrammétrie numérique [Termes IGN] image captée par drone [Termes IGN] orthophotoplan numérique [Termes IGN] précision centimétrique [Termes IGN] Rwanda [Termes IGN] scène urbaine [Termes IGN] zone urbaine Résumé : (Auteur) Aerial or satellite images are conventionally used for geospatial data collection. However, unmanned aerial vehicles (UAVs) are emerging as a suitable technology for providing very high spatial and temporal resolution data at a low cost. This paper aims to show the potential of using UAVs for map creation and updating. The whole workflow is introduced in the paper, using a case study in Rwanda, where 954 images were collected with a DJI Phantom 2 Vision Plus quadcopter. An orthophoto covering 0.095 km2 with a spatial resolution of 3.3 cm was produced and used to extract features with a sub-decimetre accuracy. Quantitative and qualitative control of the UAV data products were performed, indicating that the obtained accuracies comply to international standards. Moreover, possible problems and further perspectives were also discussed. The results demonstrate that UAVs provide promising opportunities to create high-resolution and highly accurate orthophotos, thus facilitating map creation and updating. Numéro de notice : A2018-442 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1080/00396265.2016.1268756 Date de publication en ligne : 30/12/2016 En ligne : https://doi.org/10.1080/00396265.2016.1268756 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=91014 [article]

Real-time relative mobile target positioning using GPS-assisted stereo videogrammetry / Bahadir Ergun in Survey review, vol 50 n° 361 (July 2018)  

Public [article]  inSurvey review > vol 50 n° 361 (July 2018) . - pp 326 - 335 Titre : Real-time relative mobile target positioning using GPS-assisted stereo videogrammetry Type de document : Article/Communication Auteurs : Bahadir Ergun, Auteur ; Irfan Sayim, Auteur ; Cumhur Sahin, Auteur ; N. Tok, Auteur Année de publication : 2018 Article en page(s) : pp 326 - 335 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image [Termes IGN] détection de cible [Termes IGN] image vidéo [Termes IGN] photogrammétrie métrologique [Termes IGN] Vidéogrammétrie Résumé : (Auteur) Positioning of a GPS-equipped (Global Positioning System) moving target was determined by stereo-videogrammetry from two images of cameras where they were placed on another GPS-equipped moving platform. The computed position outputs of target were compared with the relative positions obtained from two GPS receivers. The target, a small square-like pattern, was tracked from a certain distance depending on the base distance between the cameras. The video files were created from acquired images data. These video files were used in real-time computation to get the target image position for every film frame. First, the location of target was computed within video film frames. Since the target cannot be searched on the whole picture, maximum pixel length, which the target can travel on the consecutive film frames was considered as offset. Therefore, the search was made over a small area rather than whole picture. That was improved the performance of positioning. Finally, videogrammetrically computed coordinates for all epochs were compared with GPS-based relative distances to justify performance of relative target positioning results. Numéro de notice : A2018-443 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1080/00396265.2016.1267303 Date de publication en ligne : 27/12/2016 En ligne : https://doi.org/10.1080/00396265.2016.1267303 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=91015 [article]

The impact of solid Earth-tide model error on tropospheric zenith delay estimates and GPS coordinate time series / Fei Li in Survey review, vol 50 n° 361 (July 2018)  

Public [article]  inSurvey review > vol 50 n° 361 (July 2018) . - pp 355 - 363 Titre : The impact of solid Earth-tide model error on tropospheric zenith delay estimates and GPS coordinate time series Type de document : Article/Communication Auteurs : Fei Li, Auteur ; Jintao Lei, Auteur ; Chao Ma, Auteur ; Weifeng Hao, Auteur ; et al., Auteur Année de publication : 2018 Article en page(s) : pp 355 - 363 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] coordonnées GPS [Termes IGN] erreur de modèle [Termes IGN] marée terrestre [Termes IGN] propagation du signal [Termes IGN] retard troposphérique zénithal [Termes IGN] série temporelle Résumé : (Auteur) Any unmodelled or mismodelled subdaily signals left in the model may not only affect the instantaneous site positions and the associated estimates, but also propagate into spurious seasonal signals, contaminating the daily coordinate time series. To demonstrate how subdaily ‘error’ in the modelling of the solid Earth-tide affects the estimates of tropospheric zenith total delay (ZTD) and how it propagates into long-period signal in the daily GPS time series, we analyse GPS observations collected between 2009 and 2013 for 13 sites in the coastal regions of Antarctica using the GAMIT/GLOBK 10.6 software. We find that ZTD differenced time series, with amplitude at 2 mm level, have inverse correlation with the input K1 correction, and the corresponding admittances range from 6% to 14%; Propagated spurious annual signals are evident in the vertical component of coordinate differenced time series, with amplitudes at the mm level and admittances of around 2–11%. Numéro de notice : A2018-444 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1080/00396265.2016.1277657 Date de publication en ligne : 12/01/2017 En ligne : https://doi.org/10.1080/00396265.2016.1277657 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=91018 [article]

Comparative analysis of multi-constellation GNSS single-frequency precise point positioning / Mahmoud Abd Rabbou in Survey review, vol 50 n° 361 (July 2018)  

Public [article]  inSurvey review > vol 50 n° 361 (July 2018) . - pp 373 - 382 Titre : Comparative analysis of multi-constellation GNSS single-frequency precise point positioning Type de document : Article/Communication Auteurs : Mahmoud Abd Rabbou, Auteur ; Adel El-Shazly, Auteur ; Kamal Ahmed, Auteur Année de publication : 2018 Article en page(s) : pp 373 - 382 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement [Termes IGN] analyse comparative [Termes IGN] positionnement par BeiDou [Termes IGN] positionnement par Galileo [Termes IGN] positionnement par GLONASS [Termes IGN] positionnement par GPS [Termes IGN] positionnement ponctuel précis [Termes IGN] récepteur GNSS [Termes IGN] récepteur monofréquence Résumé : (Auteur) We develop new single-frequency PPP models, which combine the observations of the current GNSS constellations, including GPS, GLONASS, Galileo and BeiDou. Four single-frequency GNSS PPP models are developed, namely, the undifferenced single-frequency GNSS PPP model, the undifferenced ionosphere-free (IF) code and phase model known as quasi-phase model, the between-satellite-single-difference model (BSSD) and the between-satellite-single-difference ionosphere-free (BSSDIF) model. The IGS final precise products are used to account for the orbital and clock errors. For both undifferenced and BSSD models, the IGS final global ionospheric maps (GIM) model is used to correct the ionospheric delay. The GNSS inter-system biases are treated as additional unknowns in the estimation process for the undifferenced models, while a loosely coupled technique is used for the BSSD models. Various GNSS combinations are considered in the assessment for each PPP model, including GPS/GLONASS, GPS/Galileo, GPS/BeiDou and quad-constellation GNSS observations. It is shown that the multi-GNSS observations enhance the PPP solution accuracy in comparison with the GPS-only solution. Furthermore, the use of IF-PPP technique enhances the positioning accuracy by 25, 20, 24, 20 and 19% compared with the GIM-based PPP model for the GPS-only, GPS/GLONASS, GPS/Galileo, GPS/BeiDou and quad-GNSS combinations, respectively, for 1 h of GNSS data processing. In addition, an average of 15% positioning accuracy improvement can be obtained when the BSSD techniques are used compared with the undifferenced techniques. However, for 6 h of processing, comparable positioning accuracy can be obtained from all four single-frequency models. Numéro de notice : A2018-445 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1080/00396265.2017.1296628 Date de publication en ligne : 13/03/2017 En ligne : https://doi.org/10.1080/00396265.2017.1296628 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=91030 [article]