Photogrammetric Block Adjustment Research Articles

HYBRID GEOREFERENCING, ENHANCEMENT AND CLASSIFICATION OF ULTRA-HIGH RESOLUTION UAV LIDAR AND IMAGE POINT CLOUDS FOR MONITORING APPLICATIONS

Abstract. This paper presents a study on the potential of ultra-high accurate UAV-based 3D data capture by combining both imagery and LiDAR data. Our work is motivated by a project aiming at the monitoring of subsidence in an area of mixed use. Thus, it covers built-up regions in a village with a ship lock as the main object of interest as well as regions of agricultural use. In order to monitor potential subsidence in the order of 10 mm/year, we aim at sub-centimeter accuracies of the respective 3D point clouds. We show that hybrid georeferencing helps to increase the accuracy of the adjusted LiDAR point cloud by integrating results from photogrammetric block adjustment to improve the time-dependent trajectory corrections. As our main contribution, we demonstrate that joint orientation of laser scans and images in a hybrid adjustment framework significantly improves the relative and absolute height accuracies. By these means, accuracies corresponding to the GSD of the integrated imagery can be achieved. Image data can also help to enhance the LiDAR point clouds. As an example, integrating results from Multi-View Stereo potentially increases the point density from airborne LiDAR. Furthermore, image texture can support 3D point cloud classification. This semantic segmentation discussed in the final part of the paper is a prerequisite for further enhancement and analysis of the captured point cloud.

Toward high-resolution global topography of Mercury from MESSENGER orbital stereo imaging: A prototype model for the H6 (Kuiper) quadrangle

We selected approximately 10,500 narrow-angle camera (NAC) and wide-angle camera (WAC) images of Mercury acquired from orbit by MESSENGER's Mercury Dual Imaging System (MDIS) with an average resolution of 150m/pixel to compute a digital terrain model (DTM) for the H6 (Kuiper) quadrangle, which extends from 22.5°S to 22.5°N and from 288.0°E to 360.0°E. From the images, we identified about 21,100 stereo image combinations consisting of at least three images each. We applied sparse multi-image matching to derive approximately 250,000 tie-points representing 50,000 ground points. We used the tie-points to carry out a photogrammetric block adjustment, which improves the image pointing and the accuracy of the ground point positions in three dimensions from about 850m to approximately 55m. We then applied high-density (pixel-by-pixel) multi-image matching to derive about 45 billion tie-points. Benefitting from improved image pointing data achieved through photogrammetric block adjustment, we computed about 6.3 billion surface points. By interpolation, we generated a DTM with a lateral spacing of 221.7m/pixel (192 pixels per degree) and a vertical accuracy of about 30m. The comparison of the DTM with Mercury Laser Altimeter (MLA) profiles obtained over four years of MESSENGER orbital operations reveals that the DTM is geometrically very rigid. It may be used as a reference to identify MLA outliers (e.g., when MLA operated at its ranging limit) or to map offsets of laser altimeter tracks, presumably caused by residual spacecraft orbit and attitude errors. After the relevant outlier removals and corrections, MLA profiles show excellent agreement with topographic profiles from H6, with a root mean square height difference of only 88m.

The northern hemisphere of asteroid (21) Lutetia—topography and orthoimages from Rosetta OSIRIS NAC image data

During the flyby at asteroid (21) Lutetia by the Rosetta spacecraft in July 2010, the OSIRIS imaging system onboard acquired several hundred images of Lutetia's surface. Images of the OSIRIS NAC (Narrow Angle Camera) comprise up to 60m/pixel ground resolution. We analyzed 84 multi-spectral NAC images with stereo-photogrammetric methods. A 3D point control network within a photogrammetric block adjustment was used to derive improved orientation data (pointing and position) for the Rosetta spacecraft as well as corrections of the pre-flight estimates of Lutetia's position in space. For the generation of a digital terrain model (DTM), we selected a subset of 10 OSIRIS NAC images within a multi-image matching process. We combined the matching results with the adjusted orientation data and derived more than 12 million of surface points with a 3D point accuracy of ∼40m (2/3pixel) and a vertical component of that of ∼15m (1/4pixel). The 3D surface points were converted to a final 60m raster DTM, which covers about 78% of the entire northern hemisphere. All 84 NAC images were then ortho-rectified on the basis of the improved orientation and the DTM. Thus, orthoimage products with sub-pixel registration accuracy are available for multi-spectral mapping of the surface of Lutetia. Finally, the DTM was textured with an orthoimage mosaic to form a VRML dataset for full-resolution interactive 3D investigations.

A strip adjustment procedure to mitigate the impact of inaccurate mounting parameters in parallel lidar strips

AbstractLidar (laser scanning) technology has been proven as a prominent technique for the acquisition of high‐density and accurate topographic information. Because of systematic errors in the lidar measurements (drifts in the position and orientation information and biases in the mirror angles and ranges) and/or in the parameters relating the system components (mounting parameters), adjacent lidar strips may exhibit discrepancies. Although position and orientation drifts can have a more significant impact, these errors and their impact do not come as a surprise if the quality of the GPS/INS integration process is carefully examined. Therefore, the mounting errors are singled out in this work. The ideal solution for improving the compatibility of neighbouring strips in the presence of errors in the mounting parameters is the implementation of a rigorous calibration procedure. However, such a calibration requires the original observations, which may not be usually available. In this paper, a strip adjustment procedure to improve the compatibility between parallel lidar strips with moderate flight dynamics (for example, acquired by a fixed‐wing aircraft) over an area with moderately varying elevation is proposed. The proposed method is similar to the photogrammetric block adjustment of independent models. Instead of point features, planar patches and linear features, which are represented by sets of non‐conjugate points, are used for the strip adjustment. The feasibility and the performance of the proposed procedure together with its impact on subsequent activities are illustrated using experimental results from real data.

Use of generalised Procrustes analysis for the photogrammetric block adjustment by independent models

The paper reviews at first some aspects of the generalised Procrustes analysis (GP) and outlines the analogies with the block adjustment by independent models. On this basis, an innovative solution of the block adjustment problem by Procrustes algorithms and the related computer program implementation are presented and discussed. The main advantage of the new proposed method is that it avoids the conventional least squares solution. For this reason, linearisation algorithms and the knowledge of a priori approximate values for the unknown parameters are not required. Once the model coordinates of the tie points are available and at least three control points are known, the Procrustes algorithms can directly provide, without further information, the tie point ground coordinates and the exterior orientation parameters. Furthermore, some numerical block adjustment solutions obtained by the new method in different areas of North Italy are compared to the conventional solution. The very simple data input process, the less memory requirements, the low computing time and the same level of accuracy that characterise the new algorithm with respect to a conventional one are verified with these tests. A block adjustment of 11 models, with 44 tie points and 14 control points, takes just a few seconds on an Intel PIII 400 MHz computer, and the total data memory required is less than twice the allocated space for the input data. This is because most of the computations are carried out on data matrices of limited size, typically 3×3.

Differential GPS: Efficient Tool in Photogrammetry

In the photogrammetric mapping process, a reduction of the amount of ground control can be realized when the position of the aerial camera, or to be more precise the position of its projection center, is determined during the flight. In this paper the results of a testflight performed to investigate the use of differential GPS for this position determination are discussed. From a testfield with extensive ground control, 360 photographs were taken in twelve different strips. Using two different photogrammetric block-adjustment methods, the coordinates of the projection centers were determined for two different block-configurations.

Inertial surveying for the purpose of survey control densifications — A trial and comparison with photogrammetric block adjustment

Abstract Space technology has come down to earth and is no w applied in ordinary surveying tasks. Surveying techniques using satellites, interferometry and inertial systems are becoming increasingly important. This report empirically assesses an Inertial Survey System: it describes the planning and field procedures of survey control densifications with an average separation of 250 m and compares the results technically and economically with a photogrammetric block adjustment previously carried out over the same area. The Inertial Survey System gave double-run accuracies with a standard deviation (σ) of σx = 4.6 cm, σy = 4.4 cm and σz = 2.1 cm; operations were smooth and quick (6.6 minutes per point). It is argued that the FERRANTI Inertial System proved to be an accurate, rapid and economical alternative for control densification. For 50 points, costs per point for photogrammetric block adjustment and Inertial Survey System (I.S.S.) were identical ($100/point). For 100 points or more photogrammetric block...

The Use of Relative Terrestrial Control Data in SPACE-M Photogrammetric Block Adjustments

The formulation of the photogrammetric block adjustment program SPACE-M has recently been extended to use relative terrestrial information. Such relative data are readily available from local survey networks with unknown biases in translation and/or orientation and/or scale with respect to the geodetic datum. The formulation in terms of coordinate differences is briefly discussed with test results using various simulated and real data sets. The implications for topographical mapping and related applications are outlined with preliminary recommendations.

The Use of Auxiliary Airborne Sensor Data in SPACE-M Photogrammetric Block Adjustments

The mathematical formulation used in the photogrammetric block adjustment program SPACE-M has recently been extended to accommodate auxiliary airborne sensor data corresponding to the position and/or attitude of the aerial camera at the time of film exposure. Examples of such systems are statoscopes, laser profilometers, Inertial Navigation Systems (INS) and the Global Positioning System (GPS). The description of the use of these auxiliary data in SPACE-M is outlined and references are given to other related formulations. Test results with simulated and limited real data are presented with some analysis of the implications for topographical mapping and other applications.

On precision requirements for integrated survey control densification by photogrammetric block adjustment

The paper derives a method to establish the precision to be met by a net of coordinated points determined by photogrammetric block adjustment, when the precision specifications for relocation of property boundaries from this net of points are given. The method discussed is of importance to both the problems of planning and of evaluation. Practical examples are used to illustrate these points.

Photogrammetric Block Adjustment

Photogrammetric Block Adjustment

Co-ordination of survey marks by photogrammetry

Reports on the effectiveness of combining South Australian field survey and photogrammetric block adjustment procedures to derive the coordinates of survey marks. Preliminary analysis was made of factors contributing towards accidental and systematic errors. The conclusion is that a gain in economy and efficiency can be achieved.