Calculation Of Aspects Research Articles

Fast slope algorithm with the use of vectorization and parallelization for multicore architectures

The slope calculation algorithm is one of the most widely used geospatial algorithms employing the 3x3 moving window technique (along with calculation of aspect, curvature and flow direction). This work presents an approach consisting of transforming a slope algorithm from a sequential form into a version that can exploit vector and parallel traits of multicore architectures with vector instructions. This approach allows us to take advantage of the potential of the modern multicore processors. The basic idea for optimizing the 3x3 moving window computation is to split the equation used to calculate the result into parts that operate on data that are known to exist in adjacent memory locations. The research was conducted on two multicore architectures without the change in the code — the older architecture was Sandy Bridge and the newer one was Haswell (with more cores). The efficiency of the developed slope algorithm was verified in practice with the use of DEM files of the same resolution but of different sizes. We showed through the numerical experiments that our approach gives better time performance than the original algorithm (and other tools) — and with no loss of accuracy.

An acute stroke CT imaging algorithm incorporating automated perfusion analysis.

In this paper, we propose a CT imaging algorithm for patients presenting with suspected acute stroke that incorporates automated CT perfusion(CTP) imaging. The algorithm details evaluation of the non-contrastCT (NCCT) for hemorrhage and acute ischemia, calculation of ASPECTS, with performance and interpretation of CTP if appropriate. In particular, we consider the key steps in expeditious interpretation of non-contrast CT and CT angiography in the context of suspected acute ischemic stroke. Given the recent expansion of the "imaging based" treatment window for thrombectomy from 6 to 24h in the 2018 American Heart Association stroke guidelines, we consider the key criteria in the decision to perform CT perfusion and the patient cohorts in which this might be most helpful. We also describe how imaging findings might be incorporated into the treatment paradigm for suspected with acute ischemic stroke and we allude to some of the most frequently encountered pitfalls associated with CTP which we think will be particularly helpful for radiologists and stroke physicians who are considering adding CT perfusion to their work-up for acute stroke.

Effect of rounding off elevation values on the calculation of aspect and slope from a gridded digital elevation model

Slope and aspect derived from digital elevation models are important variables used regularly in geographical information systems for modelling purposes. Digital elevation models (DEMs) have become a very common and widely used source for creating slope and aspect map surfaces. However, quite often these map surfaces are created and used without due consideration being given to the accuracy of the DEMs and the algorithms used to derive slope and aspect surfaces. The purpose of this paper is to show the flaws in some of the algorithms used to generate aspect and slope information from gridded digital elevation models and to make users aware of problems or errors that may be encountered. The research shows that the precision to which elevation values are stored in a DEM strongly influences the derived products of aspect and, to a lesser extent, slope.