Afonine, Pavel V.Ī Detailed Geomorphological Sketch Map of Titan's Afekan Crater Region Finally, this model-based metric was used to evaluate map sharpening and to evaluate map-sharpening approaches, and it was found that optimization of the adjusted surface area can be an effective tool for map sharpening.« less The map–model correlation is calculated using a model withBfactors (atomic displacement factors ADPs) set to zero. To evaluate the performance of various approaches, a simple metric based on map–model correlation that can reproduce visual choices of optimally sharpened maps was used. Map sharpening by optimization of the adjusted surface area can be carried out for a map as a whole or it can be carried out locally, yielding a locally sharpened map. This metric was used to choose optimal map-sharpening parameters without reference to a model or other interpretations of the map. By combining these two measures inmore » a metric termed the `adjusted surface area', map quality can be evaluated in an automated fashion. The connectivity of the sharpened map is reflected in the number of connected regions defined by the same iso-contour surfaces, where a map with high connectivity has a small number of connected regions. The detail in the map is reflected in the surface area of an iso-contour surface that contains a fixed fraction of the volume of the map, where a map with high level of detail has a high surface area. Afonine, Pavel V.Īn algorithm for automatic map sharpening is presented that is based on optimization of the detail and connectivity of the sharpened map. from AuthorĪutomated map sharpening by maximization of detail and connectivity The computed detailed declination values were found to compare less favourably with observed values of declination than declination values computed from the IGRF 1985 model itself. In spite of this conclusion, declination values were computed using a common main-field model for the entire United States to see how well they compared with observed values. Because this was not done, accurate declination values cannot be determined. This could be realized only if all of the survey data were corrected to a common epoch, at which time a main-field vector model was known, before the anomaly values were computed. It was hoped that declination details could be derived from the information contained in the existing magnetic anomaly map of the United States. Modern declination charts of the United States show almost no details. An attempt to obtain a detailed declination chart from the United States magnetic anomaly map