No description available.

No description available.

No description available.

In every part of the world the rate of map revision is alarmingly low, when compared to the rate of change of many human influenced surface features. Map making is very time-consuming and often information used for updates has become history before the updated map is made available. There is therefore a requirement to regularly gather up-to-date information about surface features and to incorporate changes in maps both quickly and efficiently. Automation of two systems, i.e. the automation of map-image registration and then of change detection can fulfill the requirements of map revision. This thesis works on the first system. The piece of work in this study has looked into a fast and an accurate solution to register high resolution satellite images to maps. This will allow changes in ground features to be used to update maps. Photogrammetric techniques used to update maps have previously shown good results, but they are tedious, time-consuming, and not beneficial for updating small changes at all. Feature extraction methods were used in the present study. The system developed was designed for automatic extraction of suitable areal features in images. The emphasis was on areal features rather than point or linear features because they have a distinctive shape, and they are extracted easily from vector as well as raster data. The extraction of suitable polygons, as control information, from images was obtained by using two matching techniques. Patch matching to extract the conjugate map and image polygons, and dynamic programming to find the corresponding matched boundary pixels of the map and image polygons. Some matched points were incorrect because of perspective, shadows and occlusions. A statistical model was developed to remove perspective distortion and large errors. The model demonstrated the removal of erroneous match points, and selected the good match points and registered the images to maps with a sub-pixel accuracy. A novel aspect of the study is that the automation is achieved with high accuracy in flat and moderate terrain areas without using height information, as it is essentially used in photogrammetric techniques.

No description available.

No description available.

The Parn8.1ba Basin is one of the three large Palaeozoic intracratonic basins found in Brazil, the others being the Amazon and Parana. Parnaiba is an ovalshaped basin situated in NE Brazil and its area is about 600.000 km2 • Gravity data have been collected mainly along accessible roads crossing the Parn81ba Basin and merged with existing data bases of several Brazilian Institutions. The collection of all available geological and geophysical data included several gravity profiles crossing the eastern half of the basin. These profiles are part of a much larger data set forming polygons over a large proportion of the Brazilian territory. The whole gravity network has been internally adjusted and referred to the International Gravity Standardization Net 71. The net has been found precise to ±0.041 mGal. Although the distribution of gravity stations is not ideal, Bouguer and free-Air anomaly maps have been produced, these being the first gravity maps for the whole basin. Contrary to the basin physiography, the Bouguer map unexpectedly shows elongated gravity lows with NE-SW and NNW -SSE directions. These are parallel to the 'l'ransbrasiliano Lineament and subparallel to the Araguaia Fold Belt, respectively. A first attempt at interpreting the gravity anomalies resulted in the proposal of an anomalous, denser zone at lower crustal depths. The tectonic subsidence in the basinal area was estimated through systematic backstripping using 22 boreholes which reached the metamorphic or sedimentary basement. A non-uniform lithospheric stretching model was used as a first approximation for the modelling of the tectonic regime. This procedure was suggested by the presence of several grabenlike structures, as confirmed by shallow seismic sections, exploratory boreholes and gravity maps. Assuming an elastic rheology for the lithosphere, a regional W-E tectonic subsidence profile could be reproduced employing an axisymmetric subsurface load and a flexural ridigity of 0.2 x 1024 N m. Results of the present study are consistent with the apparent bimodality of the flexural ridigity of the continental lithosphere.

A procedure to upward continue magnetic anomalies observed on an irregular surface onto a horizontal plane has been developed and applied to the aeromagnetic map of Great Britain. Pseudogravimetric transformation was then carried out on this reduced anomaly and both data sets have been used for analysis and interpretation of several prominent anomalies in Scotland along the Great Glen fault and over the Midland Valley. A prominent linear positive magnetic anomaly occurring along the Great Glen fault has been modelled as due to a locally magnetized outward dipping body almost symmetrical about its apex beneath the fault line, together with a magnetized crustal slab to the northwest of the fault. The outward dipping body has its top lying within the upper crust, a magnetization of greater than about 1.0 A/m, a half-width of about 40 km at its base and a thickness of the order of 7-18 km. The origin of the outward dipping magnetized body may possibly be explained by metamorphism produced by frictional heating resulting from the transcurrent fault movement. Alternatively the metamorphism may be associated with some other fault related process such as crustal fluid flow. Thermal modelling has been used to demonstrate this. The magnetization contrast across the fault may be the direct result of blocks of differing magnetization on opposite side, juxtaposed as a result of transcurrent movement. The modelling along a profile over the Clyde Plateau (Midland Valley of Scotland) using a well-constrained lava body reveals the presence of a long wavelength anomaly component due to a deeper crustal source. The basement anomaly is conspicuous on the pseudogravimetric map but not on the aeromagnetic map. A near circular magnetic anomaly near Bathgate in the Midland Valley can be explained by an unexposed intrusive body superimposed on the deep crustal source as above.

Thesis (M.S.)--Ohio State University. / Bibliography: leaves 155-158. Available online via OhioLINK's ETD Center

Thesis (Masters) -- California Institute of Technology, 1936. / Title from home page (viewed 04/20/10). Includes bibliographic references.