Quasigeoid Fitting to the GNSS/Levelling Benchmarks in Iasi City Area

Chirila, Constantin

doi:10.5593/sgem2014/b22/s9.052

Cited by 1 publication

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“…GNSS measurements were performed in static mode and led to accuracies of ellipsoidal heights of ±2-3 cm. On the other hand, the leveling measurements were carried out in the form of polygonal traverses, resulting in millimeter accuracies for the Black Sea-1975 normal heights of the new points [46]. The geospatial control network consists of 71 leveling points (Figure 7a) marked by metallic bold markers encapsulated in metallic shields (Figure 7b) or in concrete (Figure 7c) and embedded in the ground surface, of which 9 are located outside the study area.…”

Section: Leveling Points Of the Geospatial Control Networkmentioning

confidence: 99%

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Proposed Methodology for Accuracy Improvement of LOD1 3D Building Models Created Based on Stereo Pléiades Satellite Imagery

Breaban

Oniga²,

Chirila³

et al. 2022

Remote Sensing

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Three-dimensional city models play an important role for a large number of applications in urban environments, and thus it is of high interest to create them automatically, accurately and in a cost-effective manner. This paper presents a new methodology for point cloud accuracy improvement to generate terrain topographic models and 3D building modeling with the Open Geospatial Consortium (OGC) CityGML standard, level of detail 1 (LOD1), using very high-resolution (VHR) satellite images. In that context, a number of steps are given attention (which are often (in the literature) not considered in detail), including the local geoid and the role of the digital terrain model (DTM) in the dense image matching process. The quality of the resulting models is analyzed thoroughly. For this objective, two stereo Pléiades 1 satellite images over Iasi city were acquired in September 2016, and 142 points were measured in situ by global navigation satellite system real-time kinematic positioning (GNSS-RTK) technology. First, the quasigeoid surface resulting from EGG2008 regional gravimetric model was corrected based on data from GNSS and leveling measurements using a four-parameter transformation, and the ellipsoidal heights of the 142 GNSS-RTK points were corrected based on the local quasigeoid surface. The DTM of the study area was created based on low-resolution airborne laser scanner (LR ALS) point clouds that have been filtered using the robust filter algorithm and a mask for buildings, and the ellipsoidal heights were also corrected with the local quasigeoid surface, resulting in a standard deviation of 37.3 cm for 50 levelling points and 28.1 cm for the 142 GNSS-RTK points. For the point cloud generation, two scenarios were considered: (1) no DTM and ground control points (GCPs) with uncorrected ellipsoidal heights resulting in an RMS difference (Z) for the 64 GCPs and 78 ChPs of 69.8 cm and (2) with LR ALS-DTM and GCPs with corrected ellipsoidal height values resulting in an RMS difference (Z) of 60.9 cm. The LOD1 models of 1550 buildings from the Iasi city center were created based on Pléiades-DSM point clouds (corrected and not corrected) and existing building sub-footprints, with four methods for the derivation of the building roof elevations, resulting in a standard deviation of 1.6 m against high-resolution (HR) ALS point cloud in the case of the best scenario. The proposed method for height extraction and reconstruction of the city structure performed the best compared with other studies on multiple satellite stereo imagery.

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Section: Leveling Points Of the Geospatial Control Networkmentioning

confidence: 99%

“…For the case study, the construction of matrix A was chosen based on the basic model with 4 unknown parameters, considering that the application of a complex model with 5 or 7 parameters will not significantly improve the results [46]:…”

Section: Creating the Local Quasigeoid Modelmentioning

confidence: 99%