Geometric correction

Cartosat-1 is a global high-resolution stereoscopic imaging mission to support enhanced applications in several areas of terrain mapping, natural resources management, disaster management, infrastructure and develop0ment planning. A collaborative project of generating state-wide Digital Elevation Model (DEM) and a mosaic of Ortho-images for all the states and union territories in India has been completed within the project Space-Based Information Support for Decentralized Planning (SIS-DP) using photogrammetric techniques with Cartosat-1 stereo data. Approximately 11000 stereo pairs of Cartosat-1 data were used in this process. Photogrammetric block for each state was processed using existing reference tiles and accordingly, orthoimages were generated. The paper outlines the methodology for generating state-wide Digital Elevation Models (DEM) and orthoimages. Guidelines that govern the quality of the output are discussed. Dissemination mechanism via a publically accessible web platform is described.

In 1748, Giovanni Battista Nolli (1692-1756) published his «New Map of Rome» (Nuova Pianta di Roma). This work represents the first geometrically correct representation of Rome within the city walls, and the only map deriving from a topographical survey of which the procedures are known. The map represents a precious source of information and a valid cartographic basis for the study of the successive phases of the city development.

Spatial mapping from space using high-resolution satellite sensor data instead of conventional data collection techniques widely gained popularity. This study aims to analyze the planimetric and thematic accuracy of high-resolution OrbView-3 and IKONOS orthoimages. OrbView-3 and IKONOS images of a test area were acquired and these images were geometrically corrected using rational polynomial functions to conduct accuracy assessment. 40 Ground Control Points (GCPs) generated from static Global Positioning System (GPS) survey were used in the orthorectification procedure. 182 Test Points (TPs) produced from terrestrial surveying technique were used to analyze the accuracy of orthorectifications. Root Mean Square Error (RMSE) values obtained for GCPs and TPs were used to determine the planimetric accuracy of these images. Thematic accuracy analyses were conducted in radiometric and spatial base. Transects, lines and polygons were created to analyze the radiometric quality of data sets and to determine minimum distinguishable distance and distinguishable area. Both planimetric and thematic accuracy analyses illustrated that OrbView-3 and IKONOS images could be used to create 1:10000 scale map of the concerned region with appropriate planimetric and thematic quality.

The new technology of small satellites (microsatellites) opens a new era in satellite Earth observations. Small satellites such as the ESA’s Project for On-Board Autonomy (PROBA), launched on October 22, 2001, are of interest due to their low cost, flexibility of positioning, and capability for multiangular scanning in both across-and along track directions. PROBA’s Compact High Resolution Imaging Spectrometer (CHRIS) provides multidirectional, as well as hyperspectral data at 18m resolution and is supplied mainly to the scientific community for experimental environmental applications. This research evaluates the use of various empirical models for satellite orientation and terrain modelling using multidirectional CHRIS data, and evaluates the potential of small satellites with multidirectional viewing capabilities for topographic mapping. Geometric correction and co-registration of multiangle images is essential for their use for data extraction. Ideally, rigorous mathematical mode...

This article describes the use of satellite imagery for identifying key environmental characteristics within three North African coastal lagoons (Merja Zerga, Morocco; Ghar El Melh, Tunisia and Lake Manzala, Egypt) and for detecting the major environmental changes within these environments. A combination of Landsat MSS, Landsat TM, Landsat ETM+ and ASTER imagery was acquired for the three sites for a period covering the last three decades (1972–2004). Following geometric correction and enhancement, the interpretation of the most recent image acquired for each of the three lagoons provides important insights into their current conditions. For Merja Zerga, these include the distribution of the largest channels which drain extensive inter-tidal mudflats and the two major depositional features associated with sources of freshwater. The distribution of marginal aquatic vegetation is highlighted as is the intensive use of the surrounding landscape for agriculture. Intensive agriculture around Ghar El Melh is also indicated. The influence of the Mejerda River, which was diverted away from the lagoon over 100 years ago, is shown to persist as a residual area of deltaic deposits in shallow water that has been eroded over time. Coastal processes including the direction of the alongshore sediment transport and the influence of engineering work associated with port construction can also be recognised. Within Lake Manzala, vegetated islands divide the lake into a series of sub-basins which can be clearly distinguished. The large influence of human activities within this lake can be identified and include reclamation for agriculture and the conversion of parts of the lake bed for fish farms. The historical images available for the three lagoons provide important insights into decadal scale changes, which have been greatest at Lake Manzala. Since the early 1970s large parts of the lake, in particular in the southwest where the shoreline has migrated northwards, have been reclaimed. Major engineering works, such as the El Salam Canal and road embankments, are shown to have resulted in significant lake change. The distribution of emergent vegetation within the lake has also changed. Classification of images for this lake into open water, vegetation and land enables the quantification of these changes. Between 1973 and 2003, the lake declined in area by approximately 50%. Changes at Merja Zerga over the last three decades include reconfiguration of the marine outlet and the expansion of the internal delta at the end of the Nador Canal. The images of this site clearly demonstrate the intensification of agriculture around the lagoon. The most marked changes evident within the images of Ghar El Melh concern the sand bars that separate the lagoon from the sea. Geomorphological processes operating within the coastal zone have resulted in the straightening of the bars with central sections migrating out towards the sea. Remote sensing is established as a promising application for detecting the quantitative surface cover changes in coastal lagoons and their near landscapes.

Sidescan-sonar imaging systems with digital capabilities have now been available for approximately 20 years. In this paper we present several of the various digital image processing techniques developed by the U.S. Geological Survey (USGS) and used to apply intensity/radiometric and geometric corrections, as well as enhance and digitally mosaic, sidescan-sonar images of the Monterey Bay region. New software run by a WWW server was designed and implemented to allow very large image data sets, such as the digital mosaic, to be easily viewed interactively, including the ability to roam throughout the digital mosaic at the web site in either compressed or full 1-m resolution. The processing is separated into the two different stages: preprocessing and information extraction. In the preprocessing stage, sensor-specific algorithms are applied to correct for both geometric and intensity/radiometric distortions introduced by the sensor. This is followed by digital mosaicking of the track-line strips into quadrangle format which can be used as input to either visual or digital image analysis and interpretation. An automatic seam removal procedure was used in combination with an interactive digital feathering/stenciling procedure to help minimize tone or seam matching problems between image strips from adjacent track-lines. The sidescan-sonar image processing package is part of the USGS Mini Image Processing System (MIPS) and has been designed to process data collected by any ‘generic’ digital sidescan-sonar imaging system. The USGS MIPS software, developed over the last 20 years as a public domain package, is available on the WWW at: http://terraweb.wr.usgs.gov/trs/software.html.

Precision products of high-resolution satellite data is a general requirement for resource monitoring as well as topographic map updating at larger scales. As the accuracies of the standard product of the available high resolution satellite data (including IRS-1C/1D PAN) usually varies between 400 m to 2 km, there is a need to develop more accurate products which are useful in

The geometric correction of high resolution satellite images can be carried out through generic non-parametric models that relates image to terrain coordinates. Traditional approaches to image geocoding rely on the measurement of a sufficient number of GCPs in both the ground and the image reference systems. Non-parametric models require a large number of GCPs well distributed on the whole scene,

Although conventional linear 3-dimensional (3D) reconstruction of coronary arteries by intravascular ultrasound has been widely used for the assessment of plaque volume and progression; the volumetric error (VE) that is produced has not been adequately studied. Linear and geometrically correct 3D reconstruction was applied in 16 coronary arterial segments from 9 patients. Using geometrically correct reconstruction as reference, VE was assessed in 1-mm-long arterial slices. Although for the entire length of the coronary arteries VEs for lumen, external elastic membrane (EEM), and intima-media volumes were minimal (lumen VE 0.4%, -0.8 to 1.8; EEM VE 0.3%, -0.9 to 1.9; intima-media VE 0.4%, -1.4 to 2.2), the VE in each arterial slice exhibited a large variation from -15.6% to 36.2% for lumen volume, from -12.9% to 33.1% for EEM volume, and from -17.2% to 46.7% for intima-media volume, suggesting that linear reconstruction over- or underestimates the true arterial volumes. Lumen VE, EEM VE, and intima-media VE were also significantly higher in curved arterial subsegments than in relatively straight arterial subsegments (p <0.05). In conclusion, in highly curved arterial subsegments, the VE that is produced by linearly stacking the intravascular ultrasound images may be not negligible. Geometrically correct reconstruction of coronary arteries provides more reliable arterial reconstructions and plaque volume measurements. It is anticipated that clinical application of this technique will contribute to more accurate follow-up of the progression of atherosclerosis and assessment of arterial remodeling.

This research aims at to analyse the pattern and rate of shoreline changes at the El-Arish area during the period 1984-2006, which represents the time at which the El-Arish harbour has affected along the coastline. Detecting salinity distribution of the ground water is the second objective of this study. The enhanced Landsat Thematic Mapper images utilised in this study were geometrically corrected. GIS techniques were used to produce vector maps for El-Arish coastline positions and estimate shoreline displacement during the last two decades. The measured shoreline changes derived from remote sensing data indicate accretion along the western coast of El-Arish harbour with +160 m/22 yr, at a rate of +8 m/yr. However, neighbour shore is suffering from erosion with -80 m/22 yr (-4 m/yr). Downdrift erosion occurred along the eastern coast of El-Arish harbour with -140 m/22 yr, at a rate of -7 m/yr. Physical and chemical properties of the El-Arish groundwater are analysed in 48 groundwat...