Orientation of SPOT stereopairs by means of matching a relative DEM and the SRTM DEM (original) (raw)

ORIENTATION AND DEM EXTRACTION FROM ALOS-PRISM IMAGES USING THE SRTM-DEM AS GROUND CONTROL

This paper presents a methodology of image orientation and DEM extraction from ALOS-PRISM stereopairs without the use of GCPs. It uses the approximate geo-location information derived from the sensor navigation instruments and the SRTM-DEM. The method consists in the extraction of a relative DEM, which initially is not correctly geo-referenced. This relative DEM is then matched to the SRTM-DEM, allowing for the determination of positional correction to the image orientation. Although the SRTM-DEM has a much coarser resolution, the positioning accuracy of this matching method was found, in previous work, to be of the order of 5 meters in plan coordinates, using DEM patches of 5 by 5 km. Tests were realized with PRISM images of a relatively mountainous region in Portugal, with heights ranging from sea level to 1400 meters. The horizontal accuracy, assessed with 56 independent check points identified on orthophotos of 0.5 meter resolution, gave an RMSE of 2.7 m and 3.9 m in x and y directions. In terms of vertical accuracy an RMSE of 2.8 meters was found for a total of 45 ICPs measured on a DEM, derived photogrammetrically for mapping scale 1:10,000. The overall accuracy is compatible with the standards for 3D data extraction for 1:25,000 scale mapping, and has the advantage of not requiring any field survey for ground control acquisition.

SPOT Revisited: Accuracy Assessment, DEM Generation and Validation from Stereo Spot 5 HRG Images

SPOT 5 HRG Level 1A and 1B stereo scenes covering Zonguldak testfield in north-west Turkey have been analysed. They comprise the left and right image components with base to height ratio of 0.54. The pixel size on the ground is 5 m. The bundle orientation was executed by the PCI Geomatica V9.1.4 software package and resulted in 3D geopositioning to sub-pixel accuracies in each axis provided that at least six control points were used in the computation. Root mean square error (rmse) values and vectors of residual errors for Levels 1A and 1B are similar, even for different control and check point configurations. Based on the scene orientation, Level 1A and 1B digital elevation models (DEMs) of the testfield have been determined by automatic matching and validated by the reference DEM digitised from the 1:25 000 scale topographic maps, interferometric DEMs from Shuttle Radar Topography Mission (SRTM) X- and C-band SAR data and the GPS profiles measured along the main roads in the testfield. Although the accuracies of reference data-sets are too similar to the generated SPOT DEMs, these are the only high quality reference materials available in this area. Sub-pixel height accuracy was indicated by the comparison with profile points. However, they are in favourable locations where matching is always successful, so such a result may give a biased measure of the accuracy of the corresponding DEMs.

ACCURACY OF DEM GENERATION FROM TERRA-ASTER STEREO DATA

In this work we studied the accuracy of DEMs generated from ASTER stereoscopic images by automated stereo-matching techniques with two different softwares (OrthoBase PRO and OrthoEngine). We compare several DEMs generated for a test area of 23 km x 28 km situated in the province of Granada (south Spain). This is an area was selected because its variable and complex topography with elevations ranging from 300m up to 2800 m.

Accuracy analysis, dem generation and validation using russian tk-350 stereo-images

The Photogrammetric Record, 2004

ABSTRACT TK-350 stereo-scenes of the Zonguldak testfield in the north-west of Turkey have been analysed. The imagery had a base-to-height ratio of 0·52 and covered an area of 200 km × 300 km, with each pixel representing 10 m on the ground. Control points digitised from 1:25 000 scale topographic maps were used in the test. A bundle orientation was executed using the University of Hanover program BLUH and PCI Geomatica OrthoEngine AE software packages. Tests revealed that TK-350 stereo-images can yield 3D geopositioning to an accuracy of about 10 m in planimetry and 17 m in height. A 40 m resolution digital elevation model (DEM) was generated by the PCI system and compared against a reference DEM, which was derived from digitised contour lines provided by 1:25 000 scale topographic maps. This comparison showed that accuracy depends mainly on the surface structure and the slope of the local terrain. Root mean square errors in height were found to be about 27 and 39 m outside and inside forested areas, respectively. The matched DEM demonstrated a systematic shift against the reference DEM visible as an asymmetric shift in the frequency distribution. This is perhaps caused by the presence of vegetation and buildings.RésuméOn a étudié des couples stéréoscopiques TK-350 sur le polygone d'essai ZONGULDAK au Nord-Ouest de la Turquie. Le rapport base-sur-altitude des couples était de 0,52 et la zone couverte atteignait 200 km × 300 km, avec une valeur au sol de chaque pixel de 10 m. On a saisi des points d'appui par numérisation à partir des cartes topographiques à l’échelle de 1:25 000. On a effectué l‘orientation des faisceaux en utilisant un ensemble de logiciels de l'Université de Hanovre tels que BLUH et « PCI Geomatica Ortho Engine AE ». Les essais ont montré que les stéréo-couples TK-350 pouvaient fournir une précision d'environ 10 m en planimétrie et 17 m en altimétrie sur le géopositionnement 3D. On a réalisé un MNA d'une résolution de 40 m avec le système PCI, que l'on a pu comparer avec un MNA de référence obtenu par numérisation des courbes de niveau des cartes topographiques au 1:25 000. La comparaison a montré que la précision dépendait essentiellement de la nature du terrain et de la pente locale. C'est ainsi que les erreurs moyennes quadratiques en altimétrie atteignent 39 m dans les zones boisées, contre 27 m en dehors. De plus, le MNA obtenu a présenté des systématismes par rapport au MNA de référence, sous la forme de décalages asymétriques dans la répartition des fréquences. La cause en est peut-être la présence de bâtiments et de végétation.ZusammenfassungIn diesem Beitrag wird über die Analyse von TK-350 Stereoszenen im Zonguldak Testfeld im Nordwesten der Türkei berichtet. Die Bilddaten hatten ein Basis-Höhenverhltnis von 0·52 und deckten ein Gebiet von 200 × 300 km mit einer Bodenpixelgröße von 10 m ab. Für den Test wurden Passpunkte aus einer Topographischen Karte im Maßstab 1:25 000 digitalisiert. Die Bündelausgleichung wurde mit dem Programmsystem BLUH der Universitt Hannover durchgeführt, weitere Analysen mit dem Paket PCI Geomatica OrthoEngine. Die Tests zeigten, dass mit TK-350 Stereoszenen eine 3D Geopositionierung mit einer Lagegenauigkeit von ca. 10 m und einer Höhengenauigkeit von 17 m möglich ist. Mit dem PCI System wurde ein DHM mit einer Gitterweite von 40 m erzeugt und mit einem Referenz-DHM, das aus digitalisierten Höhenlinien der Topographischen Karte 1:25 000 abgeleitet wurde, verglichen. Es zeigte sich, dass die Genauigkeit im wesentlich von der Gelndestruktur und der lokalen Gelndeneigung abhngt. Der mittlere quadratische Höhenfehler lag bei 27 m außerhalb von Waldgebieten und bei 39 m innerhalb von Waldgebieten. Das durch Bildzuordnung erzeugte DHM zeigte eine systematische Verschiebung gegenüber dem Referenzdatensatz, was an der asymmetrischen Verschiebung in der Hufigkeitsverteilung zu sehen ist. Diese wird vermutlich durch Vegetation und Gebude verursacht.ResumenEn este artículo se analizan imágenes estéreo TK-350 correspondientes a la zona de ensayo Zonguldak, en el noroeste de Turquía. Las imágenes tienen una razón base-altura de 0,52, cubren un área de 200 × 300 km, y tienen una resolución espacial de 10 m. Los puntos de control utilizados en el ensayo se han digitalizado a partir de mapas topográficos a escala 1:25 000 y se utilizaron los programas BLUH de la Universidad de Hannover y Geomatica OrthoEngine AE de PCI para la orientación. Las pruebas muestran que las imágenes estéreo TK-350 pueden alcanzar una exactitud de hasta 10 m en planimetría y de 17 m en altura en la georeferenciación 3D. Se generó un modelo digital de elevaciones (MDE) con una resolución de 40 m mediante el programa de PCI que se comparó con el MDE de referencia calculado a partir de las curvas de nivel digitalizadas de los mapas topográficos a escala 1:25 000. La comparación muestra que la exactitud depende principalmente de la estructura de la superficie y de la…

Assessment of Dem Accuracy Derived from SPOT5 High Resolution Stereoscopic Imagery

This paper describes the derivation of Digital Surface Models (DSMs) from 3-fold along-track stereoscopic SPOT-5 imagery in the scope of the HRS (High Resolution Stereoscopic) study, organized by the Centre Nacional d'Études Spatiales (CNES) and the International Society of Photogrammetry and Remote Sensing (ISPRS). The orientation of SPOT-5 is reconstructed by bundle adjustment using a functional model based on correction polynomials. It resulted in an RMS-error of 2 m in Easting, Northing and Height at 17 check points. DSMs are produced for 4 test sites, which are located in different terrain types (mountainous, moderate and urban). An automatic region growing image matching process generates a dense point cloud in image space, which later is rigorously transformed into the object space and converted into a regular spaced DSM. The comparison with a digital terrain model (DTM) of superior accuracy yields standard deviations better than 5 m (1σ) in flat and moderate terrain and...

SPOT stereo matching for Digital Terrain Model generation

1993

This paper presents a matching algorithm for automatic Digital Terrain Model (DTM) generation from SPOT satellite images that provides dense, accurate and reliable results and attacks the problem of radiometric differences between the images. The proposed algorithm is based on a modified version of the Multiphoto Geometrically Constrained Matching (MPGC). It is the first algorithm that explicitly uses the SPOT geometry in matching, restricting thus the search space in one dimension, and simultaneously providing pixel and object coordinates. This leads to an increase in reliability, and to reduction and easier detection of blunders. The sensor modelling is based on Kratky's polynomial mapping functions to transform between the image spaces of stereopairs. With their help epipolar lines that are practically straight can be determined and the search is constrained along these lines. The polynomial functions can also provide approximate values, which are further refined by the use of an image pyramid. Radiometric differences are strongly reduced by performing matching not in the grey level but in gradient magnitude images. Thus, practically only the information in stripes along the edges is used for matching. Edges that exist in only one image can be detected by subtracting quasi registered images in the upper levels of an image pyramid. The points to be matched are selected by an interest operator. Gross errors can be detected by statistical analysis of criteria that are provided by the algorithm and by a robust analysis of the heights within local neighbourhoods. The results of an extensive test using a stereo SPOT model over Switzerland will be reported. Matching with different options and the qualitative comparison of the results based on thirty thousand check points will be presented.

Accuracy Analysis of Dems Derived from Aster Imagery

ASTER acquires along track stereoscopic imagery, with a spatial resolution of 15 meters. Automatic generation of Digital Elevation Models (DEMs) from these images is a well established process, implemented in many commercial software packages. It can provide relief information for areas with poor coverage of topographic mapping. This paper presents a study of the accuracy achieved in DEMs extracted from ASTER, for an area in Portugal, using the PCI OrthoEngine software. Images were orientated with ground control points (GCP) obtained from topographic maps. Experiments were carried out in reducing the number of GCPs. A number of 5 or 6 GCPs was always required to orient the images, in order to keep the accuracy achieved with larger numbers of points. It was possible to conclude that more use could have been done of the approximate orientation provided in the image header. A grid of points derived from the sensor position and attitude, estimated by onboard equipment, is given in the i...

Photogrammetric point determination and DEM generation using MOMS-2P/PRIRODA three-line imagery

This paper describes the process of photogrammetric point determination by bundle adjustment using three-line imagery collected by MOMS-2P, the German Modular Optoelectronic Multispectral Scanner. Since May 1996 MOMS-2P is attached to the remote sensing module PRIRODA of the Russian space station MIR. Its stereo module with three differently oriented lenses allows for the acquisition of three-fold along track stereoscopic imagery. The forward and aft looking channels provide 18 m, the nadir looking high resolution (HR) channel 6 m ground pixel size. For the photogrammetric evaluation 9 image scenes of orbit T083C were composed to an approximately 415 km long image strip covering parts of Southern Germany and Austria. For the German part control points provided by AMilGeo (Amt für Militärisches Geowesen) were used as ground control, with an accuracy of 1.5 m in X, Y and Z. The navigation data are recorded simultaneously with the image lines by the MOMS-NAV package mounted next to MOMS-2P on the PRIRODA module. The orbit positions are expected to have 5 m absolute and 3 m relative accuracy. The INS data have a relative accuracy of 15 00 . Since MOMS was mounted in orbit during an extra vehicular activity (EVA), there is no precise absolute pointing knowledge of the MOMS camera axes. According to experiences of earlier MOMS data evaluations the camera geometry is simultaneously estimated by self calibration methods. Using small subsets of 12, 7 and 4 control points empirical accuracies of approximately 8 m in planimetry and 10 m in height are achieved, verified by 141 independent check points. Finally a digital elevation model is produced for the entire area (about 50 km 100 km), which is imaged by all three stereo channels. For that purpose about 700.000 points are transformed into object space using the estimated interior and exterior orientation of the bundle adjustment. The comparison with a reference digital terrain model of AMilGeo results in normally distributed height differences with a standard deviation also of 10 m, demonstrating that the achieved accuracy of point determination is valid for the entire area.

Accuracy Analysis and Surface Mapping Using Spot 5 Stereo Data

On the Spot 5 satellite stereo data can be acquired simultaneously from the HRS (high resolution stereoscopic) instrument, which comprises 2 cameras looking forward and backward, respectively, at an off-nadir angle of ± 20 degrees. Enhanced along-track pixel resolution of 5 meters shall further assure a high accuracy with respect to 3D data extraction. In this concern, an HRS study team was installed and specific test sites designated in order to validate the geometric performance of Spot 5 HRS stereo data. This paper summarizes the results which have been achieved from the validation activities of the Institute of Digital Image Processing. The investigations were carried out using a test data set acquired over the city of Barcelona. Study areas showing different topographic characteristics have been investigated. Beside pure HRS stereo data, a glimpse has been further made onto the joint use of the HRS stereo data and a supermode THR image, which is basically a nadir scene with a pixel size of 2.5 meters.

Performance evaluation of global and absolute DEMs generated from ASTER stereo imagery

2011

The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) digital stereo image could be used to generate Digital Elevation Model (DEM), which represents the terrain elevation in discrete three dimensional (3D) forms. In this research, the performance of the absolute and Global DEMs generated from ASTER stereo image is evaluated for the area of Universiti Teknologi Malaysia (UTM). In doing so, 25 Ground Control Points (GCPs) collected by Global Positioning System (GPS) instrument are used to extract an absolute ASTER DEM. Furthermore, the ASTER Global DEM (GDEM) is acquired for the study area. The accuracy of the DEMs is assessed by comparing them with 20 high accuracy points which were collected using GPS technology. Some statistical parameters such as the Mean Error (ME), Standard Deviation (SD) and Root Mean Square Error (RMSE) are determined for this purpose. The achieved results indicated that the estimated vertical accuracy of the ASTER GDEM is less than 5 m at 80% confidence for the study area while the vertical accuracy of less than 15 m is obtained for the ASTER absolute DEM, which is less than the pixel size of ASTER image. Finally, according to the achieved results, 15 m resolution of ASTER image and the selected number of check points, it can be concluded that the accuracy of DEMs is acceptable for the study area, and could be used for various geoinformation applications.