Accurate georeferencing of TLS point clouds with short GNSS observation durations even under challenging measurement conditions

2018 ◽  
Vol 12 (4) ◽  
pp. 289-301
Author(s):  
Florian Zimmermann ◽  
Christoph Holst ◽  
Lasse Klingbeil ◽  
Heiner Kuhlmann
Keyword(s):  
Weighted Least Squares ◽  
Single Point ◽  
Control Point ◽  
Point Clouds ◽  
Ground Control ◽  
Control Points ◽  
Ground Control Point ◽  
Ground Control Points ◽  
Baseline Solution ◽  
Gnss Observations

Abstract The accuracy of georeferenced TLS point clouds is directly influenced by site-dependent GNSS effects, deteriorating the accuracy of the ground control point coordinate estimation. Especially under challenging GNSS conditions, this is a crucial problem. One common approach is to minimize these effects by longer observation durations, which in turn increases the effort in time and cost. In this paper, an algorithm is proposed that provides accurate georeferencing results, even under challenging measurement conditions and short observation durations. It iteratively improves the georeferencing accuracy by determining and applying obstruction adaptive elevation masks to the GNSS observations. The algorithm is tested and assessed using the data of a field test. It is demonstrated that after only 5 minutes observation duration, the ground control point coordinates can be estimated with an accuracy of 1 to 2 cm, independent from the GNSS measurement conditions. Initial states of the elevation masks are determined from a point cloud that is georeferenced using coordinates from a single point positioning solution, enhanced by a RAIM-FDE approach. Afterwards, the coordinates are estimated in a weighted least-squares baseline solution and both, the elevation masks and the coordinate estimation, are iteratively improved. Besides the significant reduction of measurement time, the proposed algorithm allows for increasing the amount of ground control points and can be applied to other direct or indirect GNSS-based georeferencing approaches.

scholarly journals A METHOD FOR SIMULTANEOUS AERIAL AND TERRESTRIAL GEODATA ACQUISITION FOR CORRIDOR MAPPING

2015 ◽  
Vol XL-1/W4 ◽  
pp. 227-232 ◽  
Author(s):  
P. Molina ◽  
M. Blázquez ◽  
J. Sastre ◽  
I. Colomina
Keyword(s):  
Spatial Configuration ◽  
Critical Role ◽  
Control Point ◽  
Unmanned Aircraft ◽  
Ground Control ◽  
Control Points ◽  
Post Processing ◽  
Simultaneous Operation ◽  
Ground Control Points ◽  
Sensor Orientation

In this paper, we present mapKITE, a new mobile, simultaneous terrestrial and aerial, geodata collection and post-processing method. On one side, the method combines a terrestrial mobile mapping system (TMMS) with an unmanned aerial mapping one, both equipped with remote sensing payloads (at least, a nadir-looking visible-band camera in the UA) by means of which aerial and terrestrial geodata are acquired simultaneously. This tandem geodata acquisition system is based on a terrestrial vehicle (TV) and on an unmanned aircraft (UA) linked by a 'virtual tether', that is, a mechanism based on the real-time supply of UA waypoints by the TV. By means of the TV-to-UA tether, the UA follows the TV keeping a specific relative TV-to-UA spatial configuration enabling the simultaneous operation of both systems to obtain highly redundant and complementary geodata. <br><br> On the other side, mapKITE presents a novel concept for geodata post-processing favoured by the rich geometrical aspects derived from the mapKITE tandem simultaneous operation. The approach followed for sensor orientation and calibration of the aerial images captured by the UA inherits the principles of Integrated Sensor Orientation (ISO) and adds the pointing-and-scaling photogrammetric measurement of a distinctive element observed in every UA image, which is a coded target mounted on the roof of the TV. By means of the TV navigation system, the orientation of the TV coded target is performed and used in the post-processing UA image orientation approach as a Kinematic Ground Control Point (KGCP). The geometric strength of a mapKITE ISO network is therefore high as it counts with the traditional tie point image measurements, static ground control points, kinematic aerial control and the new point-and-scale measurements of the KGCPs. With such a geometry, reliable system and sensor orientation and calibration and eventual further reduction of the number of traditional ground control points is feasible. <br><br> The different technical concepts, challenges and breakthroughs behind mapKITE are presented in this paper, such as the TV-to-UA virtual tether and the use of KGCP measurements for UA sensor orientation. In addition, the use in mapKITE of new European GNSS signals such as the Galileo E5 AltBOC is discussed. Because of the critical role of GNSS technologies and the potential impact on the corridor mapping market, the European Commission and the European GNSS Agency, in the frame of the European Union Framework Programme for Research and Innovation “Horizon 2020,” have recently awarded the “mapKITE” project to an international consortium of organizations coordinated by GeoNumerics S.L.

scholarly journals DESARROLLO DE UNA METODOLOGÍA SENCILLA PARA LA GEORREFERENCIACIÓN Y MEDICIÓN DE DISTANCIAS A PARTIR DE IMÁGENES DE SATÉLITE SISTEMÁTICAMENTE GEORREFERENCIADAS

2016 ◽  
Vol 39 (1) ◽  
Author(s):  
Leonardo Gónima ◽  
Libardo E. Ruiz ◽  
Marcos E. González
Keyword(s):  
Satellite Images ◽  
Control Point ◽  
Ground Control ◽  
Gps Data ◽  
Control Points ◽  
Statistical Validation ◽  
Distance Measurements ◽  
The North ◽  
Ground Control Points ◽  
Representative Points

One of the main problems for a precise georeferencing and distance measurements from satellite images, especially in geographical zones with strong morphologic and environmental dynamics, lies not only in the difficulty for identifying ground control points (GCPs), but also in real limitations for accessing such places. In this work a relatively simple methodology is proposed for georeferencing and distance measuring from satellite images, based on the utilization of previously calculated reflectance images from the surface and then oriented toward the north (systematic georeferencing). From these images and setting a basic control point (pixel) P, measured with GPS, the other GCPs were obtained by measurements of distances defined from the P point to representative points (pixels) on the image, selected for its georeferencing. The statistical validation of the obtained results, using a different sample of GCPs measured with GPS, shows that the precision of the georeferencing and distance measurement utilizing the developed methodology is similar to that obtained by conventional procedures, such as image georeferencing from GPS data.

scholarly journals Determining the Optimal Number of Ground Control Points for Varying Study Sites through Accuracy Evaluation of Unmanned Aerial System-Based 3D Point Clouds and Digital Surface Models

Drones ◽  
2020 ◽  
Vol 4 (3) ◽  
pp. 49 ◽  
Author(s):  
Jae Jin Yu ◽  
Dong Woo Kim ◽  
Eun Jung Lee ◽  
Seung Woo Son
Keyword(s):  
Image Processing ◽  
Point Clouds ◽  
Optimal Number ◽  
Ground Control ◽  
Control Points ◽  
Widespread Application ◽  
Ground Control Points ◽  
3D Point Clouds ◽  
Surface Models ◽  
Study Sites

The rapid development of drone technologies, such as unmanned aerial systems (UASs) and unmanned aerial vehicles (UAVs), has led to the widespread application of three-dimensional (3D) point clouds and digital surface models (DSMs). Due to the number of UAS technology applications across many fields, studies on the verification of the accuracy of image processing results have increased. In previous studies, the optimal number of ground control points (GCPs) was determined for a specific area of a study site by increasing or decreasing the amount of GCPs. However, these studies were mainly conducted in a single study site, and the results were not compared with those from various study sites. In this study, to determine the optimal number of GCPs for modeling multiple areas, the accuracy of 3D point clouds and DSMs were analyzed in three study sites with different areas according to the number of GCPs. The results showed that the optimal number of GCPs was 12 for small and medium sites (7 and 39 ha) and 18 for the large sites (342 ha) based on the overall accuracy. If these results are used for UAV image processing in the future, accurate modeling will be possible with minimal effort in GCPs.

scholarly journals Reconstructing 3D coastal cliffs from airborne oblique photographs without ground control points

2014 ◽  
Vol II-5 ◽  
pp. 113-116 ◽  
Author(s):  
T. J. B. Dewez
Keyword(s):  
Laser Scanner ◽  
Point Clouds ◽  
Ground Control ◽  
Control Points ◽  
Open Door ◽  
View Point ◽  
Ground Control Points ◽  
3D Point Clouds ◽  
Coastal Cliff ◽  
Coastal Cliffs

Coastal cliff collapse hazard assessment requires measuring cliff face topography at regular intervals. Terrestrial laser scanner techniques have proven useful so far but are expensive to use either through purchasing the equipment or through survey subcontracting. In addition, terrestrial laser surveys take time which is sometimes incompatible with the time during with the beach is accessible at low-tide. By comparison, structure from motion techniques (SFM) are much less costly to implement, and if airborne, acquisition of several kilometers of coastline can be done in a matter of minutes. In this paper, the potential of GPS-tagged oblique airborne photographs and SFM techniques is examined to reconstruct chalk cliff dense 3D point clouds without Ground Control Points (GCP). The focus is put on comparing the relative 3D point of views reconstructed by Visual SFM with their synchronous Solmeta Geotagger Pro2 GPS locations using robust estimators. With a set of 568 oblique photos, shot from the open door of an airplane with a triplet of synchronized Nikon D7000, GPS and SFM-determined view point coordinates converge to X: ±31.5 m; Y: ±39.7 m; Z: ±13.0 m (LE66). Uncertainty in GPS position affects the model scale, angular attitude of the reference frame (the shoreline ends up tilted by 2&deg;) and absolute positioning. Ground Control Points cannot be avoided to orient such models.

scholarly journals PRECISION POTENTIAL OF UNDERWATER NETWORKS FOR ARCHAEOLOGICAL EXCAVATION THROUGH TRILATERATION AND PHOTOGRAMMETRY

2019 ◽  
Vol XLII-2/W10 ◽  
pp. 175-180 ◽  
Author(s):  
D. Skarlatos ◽  
F. Menna ◽  
E. Nocerino ◽  
P. Agrafiotis
Keyword(s):  
Standard Deviation ◽  
Structure From Motion ◽  
Control Point ◽  
Archaeological Site ◽  
3D Models ◽  
Ground Control ◽  
Control Points ◽  
Archaeological Excavation ◽  
Control Networks ◽  
Ground Control Points

<p><strong>Abstract.</strong> Given the rise and wide adoption of Structure from Motion (SfM) and Multi View Stereo (MVS) in underwater archaeology, this paper investigates the optimal option for surveying ground control point networks. Such networks are the essential framework for coregistration of photogrammetric 3D models acquired in different epochs, and consecutive archaeological related study and analysis. Above the water, on land, coordinates of ground control points are determined with geodetic methods and are considered often definitive. Other survey works are then derived from by using those coordinates as fixed (being ground control points coordinates considered of much higher precision). For this reason, equipment of proven precision is used with methods that not only compute the most correct values (according to the least squares principle) but also provide numerical measures of their precisions and reliability. Under the water, there are two options for surveying such control networks: trilateration and photogrammetry, with the former being the choice of the majority of archaeological expeditions so far. It has been adopted because of ease of implementation and under the assumption that it is more reliable and precise than photogrammetry.</p><p>This work aims at investigating the precision of network establishment by both methodologies by comparing them in a typical underwater archaeological site. Photogrammetric data were acquired and analysed, while the trilateration data were simulated under certain assumptions. Direct comparison of standard deviation values of both methodologies reveals a clear advantage of photogrammetry in the vertical (Z) axis and three times better results in horizontal precision.</p>

scholarly journals Geospatial Analysis of Groundwater Potential Zones in Keffi, Nassarawa State, Nigeria

2019 ◽  
pp. 1-16
Author(s):  
D. R. Abdullahi ◽  
O. O. Oladosu ◽  
S. A. Samson ◽  
L. O. Abegunde ◽  
T. A. Balogun ◽  
...  
Keyword(s):  
Spatial Data ◽  
Control Point ◽  
Drainage Density ◽  
Groundwater Potential ◽  
Ground Control ◽  
Control Points ◽  
Groundwater Potential Zones ◽  
Ground Control Points ◽  
Potential Map ◽  
Groundwater Potential Map

Aim: Employ the use of Remote Sensing and Geographic Information System (GIS) to analyze areas of groundwater potentials in Keffi LGA to meet the rate of water demand. Study Design:  The study is designed to delineate and analyze the drainage characteristics, and map out the groundwater potential zones. Place and Duration of Study: The study is conducted in Keffi LGA of Nassarawa State, Nigeria in 2018. Methodology: Both spatial and non-spatial data were utilized for this research, including Ground Control Points, satellite imageries, and maps. The data generated consisting of the rainfall, NDVI, lineament, geology, slope, and relief were prepared into thematic layers and used for the generation of the drainage morphometric parameters and multi-criteria overlay analysis. Each of the layer used has inputs were ranked based on their relative importance in controlling groundwater potential, and divided into classes using the hydro-geological properties. The groundwater potential analysis reveals four distinct zones representing high, moderate, less and least groundwater potential zones. The delineated groundwater potential map was verified using the available Ground Control Point of boreholes across the study area. Results: The drainage of the study area falls in the 4th order, with the drainage density ranging from 0.2 to 1.6. From the groundwater potential map generated using the rainfall, lineament, geology, drainage density, slope, soil, and NDVI attributes, areas categorized having the moderate groundwater potentials cover about 89.1 km2, while the least cover 0.1 km2 of the study area.  Validating the result with borehole locations across the location shows that the boreholes are dug based on the availability of water following the groundwater potentials, and; 59.8% of the settlement area falls within the moderate groundwater potential classes. Conclusion: The area has adequate capacity for water supply, and only those within the high groundwater potential classes can access groundwater throughout the year.

scholarly journals Short Communication: A simple workflow for robust low-cost UAV-derived change detection without ground control points

2019 ◽  
Author(s):  
Kristen L. Cook ◽  
Michael Dietze
Keyword(s):  
Change Detection ◽  
Low Cost ◽  
Point Clouds ◽  
Standard Approach ◽  
Ground Control ◽  
Control Points ◽  
Ground Control Points ◽  
3D Point Clouds ◽  
Tectonically Active ◽  
Comparative Accuracy

Abstract. High quality 3D point clouds generated from repeat camera-equipped unmanned aerial vehicle (UAV) surveys are increasingly being used to investigate landscape changes and geomorphic processes. Point cloud quality can be expressed as accuracy in a comparative (i.e., from survey to survey) and absolute (between survey and an external reference system) sense. Here we present a simple workflow for calculating pairs or sets of point clouds with a high comparative accuracy, without the need for ground control points or a dGPS equipped UAV. We demonstrate the efficacy of the new approach using a consumer-grade UAV in two contrasting landscapes: the coastal cliffs on the Island of Rügen, Germany, and the tectonically active Daan River gorge in Taiwan. Compared to a standard approach using ground control points, our workflow results in a nearly identical distribution of measured changes. Compared to a standard approach without ground control, our workflow reduces the level of change detection from several meters to 10–15 cm. This approach enables robust change detection using UAVs in settings where ground control is not possible.

scholarly journals Impact of UAV Surveying Parameters on Mixed Urban Landuse Surface Modelling

2020 ◽  
Vol 9 (11) ◽  
pp. 656
Author(s):  
Muhammad Hamid Chaudhry ◽  
Anuar Ahmad ◽  
Qudsia Gulzar
Keyword(s):  
Point Cloud ◽  
Large Scale ◽  
Accuracy Assessment ◽  
Computational Cost ◽  
Three Dimensional ◽  
Point Clouds ◽  
Ground Control ◽  
Control Points ◽  
Ground Control Points ◽  
High Computational Cost

Unmanned Aerial Vehicles (UAVs) as a surveying tool are mainly characterized by a large amount of data and high computational cost. This research investigates the use of a small amount of data with less computational cost for more accurate three-dimensional (3D) photogrammetric products by manipulating UAV surveying parameters such as flight lines pattern and image overlap percentages. Sixteen photogrammetric projects with perpendicular flight plans and a variation of 55% to 85% side and forward overlap were processed in Pix4DMapper. For UAV data georeferencing and accuracy assessment, 10 Ground Control Points (GCPs) and 18 Check Points (CPs) were used. Comparative analysis was done by incorporating the median of tie points, the number of 3D point cloud, horizontal/vertical Root Mean Square Error (RMSE), and large-scale topographic variations. The results show that an increased forward overlap also increases the median of the tie points, and an increase in both side and forward overlap results in the increased number of point clouds. The horizontal accuracy of 16 projects varies from ±0.13m to ±0.17m whereas the vertical accuracy varies from ± 0.09 m to ± 0.32 m. However, the lowest vertical RMSE value was not for highest overlap percentage. The tradeoff among UAV surveying parameters can result in high accuracy products with less computational cost.

scholarly journals Geocoding Error Correction for InSAR Point Clouds

2018 ◽  
Vol 10 (10) ◽  
pp. 1523 ◽  
Author(s):  
Sina Montazeri ◽  
Fernando Rodríguez González ◽  
Xiao Zhu
Keyword(s):  
Point Cloud ◽  
Point Clouds ◽  
Ground Control ◽  
Control Points ◽  
Persistent Scatterer Interferometry ◽  
Sar Images ◽  
Localization Accuracy ◽  
Ground Control Points ◽  
Persistent Scatterer ◽  
The City

Persistent Scatterer Interferometry (PSI) is an advanced multitemporal InSAR technique that is capable of retrieving the 3D coordinates and the underlying deformation of time-coherent scatterers. Various factors degrade the localization accuracy of PSI point clouds in the geocoding process, which causes problems for interpretation of deformation results and also making it difficult for the point clouds to be compared with or integrated into data from other sensors. In this study, we employ the SAR imaging geodesy method to perform geodetic corrections on SAR timing observations and thus improve the positioning accuracy in the horizontal components. We further utilize geodetic stereo SAR to extract large number of highly precise ground control points (GCP) from SAR images, in order to compensate for the unknown height offset of the PSI point cloud. We demonstrate the applicability of the approach using TerraSAR-X high resolution spotlight images over the city of Berlin, Germany. The corrected results are compared with a reference LiDAR point cloud of Berlin, which confirms the improvement in the geocoding accuracy.

scholarly journals Pemanfaatan Unmanned Aerial Vehicle (UAV) Jenis Quadcopter untuk Percepatan Pemetaan Bidang Tanah (Studi Kasus: Desa Solokan Jeruk Kabupaten Bandung)

2019 ◽  
Vol 2018 (1) ◽  
Author(s):  
Dhiky Hartono ◽  
Soni Darmawan
Keyword(s):  
Unmanned Aerial Vehicle ◽  
Control Point ◽  
Ground Control ◽  
Ground Control Point ◽  
Land Registration ◽  
Ground Control Points ◽  
Stop And Go ◽  
Aerial Vehicle ◽  
First Time ◽  
The Village

ABSTRAKPendaftaran Tanah Sistematik Lengkap (PTSL) merupakan kegiatan pendaftaran tanah untuk pertama kali yang dilakukan secara serentak di Indonesia. Program PTSL dimulai pada tahun 2016 dan ditargetkan selesai pada tahun 2025. Dengan luas darat Indonesia mencapai 2,01 juta km2, dibutuhkan teknologi yang dapat mempercepat program PTSL, di antaranya menggunakan pesawat tanpa awak (drone). Tujuan dari penelitian ini adalah untuk mengetahui sejauh mana kemampuan unmanned aerial vehicle (UAV) jenis Quadcopter untuk pemetaan bidang tanah yang ditinjau dari ketelitian, biaya, dan kecepatan. Daerah yang akan dikaji merupakan daerah yang sedang melaksanakan program PTSL yaitu Desa Solokan Jeruk Kecamatan Solokan Jeruk Kabupaten Bandung. Metodologi penelitian terdiri atas akuisisi data menggunakan UAV jenis Quadcopter dan proses pengolahan foto menggunakan perangkat lunak Agisoft Photoscan yang digeoreferensikan dengan ground control points (GCP) yang didapat dari pengamatan GPS Stop and Go. Hasil penelitian ini menunjukkan UAV jenis Quadcopter dapat mempercepat program PTSL dengan tingkat akurasi 96%, kecepatan penyediaan peta kerja atau peta dasar untuk program PTSL kurang dari 5 hari untuk luasan 1000 Ha, namun dengan biaya yang cukup tinggi.Kata Kunci: PTSL, UAV jenis Quadcopter, Ground Control Point (GCP) ABSTRACTComplete Systematic Land Registration (CSLR) is a land registration activity for the first time that is carried out simultaneously in Indonesia. The PTSL program was started in 2016 and targeted for completion by 2025. With Indonesia's land area reaching 2.01 million km2, technology is needed that can accelerate the CSLR program, one of which is using a drone. The purpose of this research is to know the extent of Unmanned Aerial Vehicle (UAV) capability of Quadcopter type for mapping of plot of land in terms of accuracy, speed, and economics. The study area is area that is being implemented the program, which located in the village of Solokan Jeruk, Solokan Sub-District, Bandung Regency. The research methodology consists of data acquisition by using UAV type Quadcopters and photo processing using Agisoft Photoscan software that will be georeferenced to the Ground Control Point (GCP) that is obtained from the GPS Real Time Kinematic observation using the Stop and Go method. The results of this study indicate that the UAV type Quadcopter can accelerate the CSLR program by providing 96% accuracy, and the speed of providing a work map or base map for CSLR program of less than 5 days for 1000 Ha, but at a high cost.Keywords: CSLR, UAV type Quadcopter, Ground Control Point (GCP)

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