Synergetic efficiency of Lidar and WorldView-2 for 3D urban cartography in Northeast Mexico

Three-dimensional urban cartography is needed for city changes’ assessment. The variety of studies using 3D calculations of urban elements grows each year. Building and vegetation volumes are necessary to assess and understand spatio-temporal urban changeable environments. However, there are technical questions as to which method can improve 3D urban cartographic accuracy. The innovative part of this current study is the creation of a six-band hybrid obtained from LIDAR and WorldView2 synergy. Two different enhancement algorithms demonstrated the most important spectral features for the urban development and vegetation classes. Results indicated an improvement in accuracy by up to 21.3%, according to the Kappa coefficient. Both infra-red band and intensity band were the most significant, according to the principal components analysis. The synergy delimited classes and polygons, as well as the direct display of information regarding heights of elements and improving the extraction of roads, buildings and vegetation classes.     

Study on the urban heat island effects and its relationship with surface biophysical characteristics using MODIS imageries

This study assesses surface urban heat island (UHI) and its associated surface physical characteristics using remote sensing approaches. TERRA/MODIS images acquired in 2005 in three different seasons were selected to generate land surface tem-perature and surface characteristics for the Changsha-Zhuzhou-Xiangtan metropolitan area in China. The intensity of urban heat is-land effects and its seasonal variations were examined. The result showed that UHI effects were significant both in the summer and the spri...     

Kinematic precise point positioning at remote marine platforms

Precise kinematic differential positioning using the global positioning system (GPS) at a marine platform usually requires a relatively short distance (e.g. <500 km) to a land-based reference station. As an alternative, precise point positioning (PPP) is normally considered free from this limiting requirement. However, due to the prerequisite of network-based satellite products, PPP at a remote marine platform may still be affected by its distance to the reference network. Hence, this paper investigates this scenario by configuring rings of reference stations with different radii centered on a to-be-positioned marine platform. Particularly, we applied ambiguity resolution at a single station to PPP by estimating uncalibrated phase delays (UPDs). We used three rings of reference stations centered on a vessel, with radii of roughly 900, 2,000 and 3,600 km, to determine satellite clocks and UPDs independently. For comparison, we also performed differential positioning based on a single reference station with baseline lengths of about 400, 1,700 and 2,800 km. We demonstrate that, despite the increasing ring-network radius to a few 1,000 km, the overall change in accuracy of the satellite clocks that are used at the vessel is smaller than 0.02 ns, and the RMS values of differences between the three sets of narrow-lane UPD estimates are around 0.05 cycles only. Moreover, the kinematic positioning accuracy of PPP is affected by the increasing ring-network radius, but can still achieve several centimeters after ambiguity resolution when the vessel is over a few 1,000 km away from the ring network, showing better performance than that of differential positioning. Therefore, we propose that ambiguity-fixed PPP can be used at remote marine platforms that support precise oceanographic and geophysical applications in open oceans.     

Automatic Change Detection in Very High Resolution Images With Pulse-Coupled Neural Networks

A novel approach based on pulse-coupled neural networks (PCNNs) for image change detection is presented. PCNNs are based on the implementation of the mechanisms underlying the visual cortex of small mammals, and, with respect to more traditional NNs architectures, such as multilayer perceptron, own interesting advantages. In particular, they are unsupervised and context sensitive. This latter property may be particularly useful when very high resolution images are considered as, in this case, an object analysis might be more suitable than a pixel-based one. The qualitative and more quantitative results are reported. The performance of the algorithm has been evaluated on a pair of QuickBird images taken over the test area of Tor Vergata University, Rome.      

Analysis of the Effects of Pansharpening in Change Detection on VHR Images

In this letter, we investigate the effects of pansharpening (PS) applied to multispectral (MS) multitemporal images in change-detection (CD) applications. Although CD maps computed from pansharpened data show an enhanced spatial resolution, they can suffer from errors due to artifacts induced by the fusion process. The rationale of our analysis consists in understanding to which extent such artifacts can affect spatially enhanced CD maps. To this end, a quantitative analysis is performed which is based on a novel strategy that exploits similarity measures to rank PS methods according to their impact on CD performance. Many multiresolution fusion algorithms are considered, and CD results obtained from original MS and from spatially enhanced data are compared.      

Automated GPS Data Analysis Service

Automatic analysis of geodetic-quality GPS data is available with the use of e-mail and ftp (file transfer program) as an interface to a computer at the Jet Propulsion Laboratory (JPL), where precise transmitter parameters – GPS ephemerides and clock errors – are computed regularly. The interface is such that e-mail from an external user causes the JPL computer to fetch the user's data. The computer than analyzes the data, and places the results in an area accessible to the user. An e-mail to the user gives information on the location of the analysis results, which the user can subsequently fetch. Operations on the JPL computer are entirely automatic, and require essentially no labor. ? 1999 John Wiley & Sons, Inc.     

A GPS-Supported Gravity Survey in the Amazon of Ecuador

The growing importance and effectiveness of the Global Positioning System (GPS) in positioning geophysical surveys is now well established. In Ecuador's Amazon basin the use of GPS was the determining factor in the successful completion of a gravity survey carried out in 1994. Over 500 gravity stations, spaced from 1 to 5 km apart and positioned by GPS, were collected in the jungle environment in the country's southeast, where the preexisting data, of variable and unknown quality, were mostly confined to areas along the major rivers. This station densification, which includes the reoccupation of selected points, contributed to increase the gravity coverage; it also allowed us to evaluate and correct 1100 preexisting data points in the area, so that the different surveys can be merged. The composite data set is used for a geologic analysis of the study area, where previously unknown structures are discovered. ? 1999 John Wiley & Sons, Inc.     

Extraction of Solar Coronal Magnetic Loops with the Directional 2D Morlet Wavelet Transform

We present an automated extraction method based on the continuous wavelet transform (CWT) for analyzing solar magnetic loops. The aim of the work is to extract, from the images taken from solar EUV telescopes, the traces of bright loops presumably shaped by the magnetic field of the solar corona. The technique is that of wavelet analysis, using the two-dimensional Morlet wavelet, because of its efficiency in detecting oriented features, which allows us to follow closely the curvature of the loops. Next, we segment the wavelet modulus image and we threshold it, both globally and locally (i.e., adaptively), in order to eliminate the remaining noise. Altogether, our method performs well, it is robust and fast, and could be used as a standard tool for analyzing large data sets expected from missions like SDO.     

TWO STRUCTURAL MODELS FOR THE WESTERN FLANK OF THE BRABANT MASSIF*

This paper is concerned with an interpretation of the Bouguer anomaly on the Western flank of the Brabant Massif (Belgium). The position, shape, and density contrast of elementary bodies in the upper part of the earth's crust are determined in a purely numerical manner. A batholith-like body and a basin-type structure both adequately account for the observed surface field, at least from a one-sided geophysical and mathematical point of view. Since seismological control is lacking the two models are representative of the ambiguity and indeterminacy of the definitions of the geologic cause of the anomalous features, if the data are restricted to gravity information alone.