Study on Parallel Calculation Method of Local Terrain Parameters

  • Key Laboratory of Virtual Geographical Environment, Ministry of Education, Nanjing Normal University, Nanjing 210023, China

Received date: 2012-11-01

  Revised date: 2012-12-01

  Online published: 2012-12-25


As the analysis region becomes wider and accuracy requirement becomes higher, the parallel method is necessary for digital terrain analysis (DTA) which is data-intensive to meet the time response requirement of customs. Local terrain factor, the fundamental parameter of digital terrain analysis, is usually calculated based on the analysis window with a certain radius (the usual value is 3×3). Its calculation result of each pixel is independent and could reflect terrain information. After analyzing of serial algorithm features of local terrain parameter, extensive study on parallel method of local terrain factor is performed in this paper taking slope for example. From the aspect of data parallelism, the strategies of the way of data division, partition granularity model and data fusion of parallel calculation of local terrain factor are analyzed, and the parallel method has been constructed. To verity the correctness and practicality of the parallel method for local terrain factor in this paper, the parallel experiment of slope algorithm is designed by using SRTM DEM with 16 300×17 400 and it has been implemented and tested on a PC cluster system. The experiment results show that: (1) with the increase of process number, the execution time of parallel computing decreases significantly for different partition granularities. When the task number equals to processing node number, the execution time is similar for the whole DEM could be read for computation task by parallel computing system at a time. (2) The parallel speedup of slope algorithm rises gradually with the increase of partition granularity. When the granularity gets growth to a certain value, the changes of speedup and efficiency are basically identical. (3) With the increase of processing node, the execution time of slope algorithm without I/O consumption decreases gradually, meanwhile the change for different granularity is consistent. (4) The main influence factor of execution time is caused by reading and writing data. The efficiency of I/O determines the parallel efficiency to a great extent. So, the research indicates that the parallel method is efficient in completing the parallelization of sequential algorithms of local terrain factor, and the execution efficiency of algorithms could be increased greatly by using the parallel method which processes a good performance. The presentment and implementation of the parallel method can also provide a reference for the parallelization of the algorithm with the similar matrix type data.

Cite this article

JIANG Ling, SHANG Guo-An, LIU Kai, SONG Xiao-Dong, YANG Jian-Yi, ZHANG Gang . Study on Parallel Calculation Method of Local Terrain Parameters[J]. Journal of Geo-information Science, 2012 , 14(6) : 761 -767 . DOI: 10.3724/SP.J.1047.2012.00761


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