基于C语言的SEG-Y数据格式分析与转化

SEG- Y data format analysis and conversion based on C language

在地震数据资料存储与交换中,SEG-Y数据格式应用最为广泛.然而,由于CPU架构之间的差异,同一个SEG-Y文件并不能在具有不同CPU架构的计算机上直接读取.为了实现在不同CPU架构的计算机之间进行地震数据共享,基于标准的SEG-Y数据格式和C语言可移植性强的特点,对SEG-Y数据格式的结构构成进行了分析,分别给出了不同结构部分详细的转化算法.最常用的两种地震数据存储格式是32位IBM和IEEE浮点数格式.在研究了这两种浮点数存储结构、表示范围、精度分析和转化差异的基础上,分别给出了两种相互转化的算法并比较了不同算法的转化效率.对比文献中给出的其他编程语言编写的SEG-Y数据某部分转化程序,给出了完整的SEG-Y数据格式转化的C语言代码.实现了SEG-Y数据在不同CPU架构的计算机中的正确读取、改写与存储.良好的可移植性保证了地震数据的共享与应用.

SEG-Y data format has been widely applied in the seismic data storage and interchange. Because of the difference of CPU architecture of computer, however, a type of SEG-Y file cannot be read or save directly from different CPU architecture of computer. It is of great importance for seismic data processing and interpretation to share the seismic data between different CPU architecture of computer. To achieve it,based on the standard SEGY data format and the characteristic of highly portable of C language,we analyze the structure of SEG-Y data format and demonstrate the conversion methods for different structures in detail,respectively. The SEG-Y data format contains 3200 bytes EBCDIC code instruction text file,400 bytes binary file head,240 bytes trace head per trace and seismic data record for this trace. The most commonly used two kinds of seismic data storage format is the 32-bit IBM floating-point format and the 32-bit IEEE floating-point format.On the basis of study the 32-bit IBM floating-point format and the32-bit IEEE floating-point format storage structure, representing domain,precision analysis and conversion of differences, I put forward two kinds of algorithms for conversion from one to another,respectively. They are two kinds of algorithms which converting the32-bit IBM floating-point format to the 32-bit IEEE floating-point format. The efficiency of algorithms is different. Similarly,algorithms which converting the 32-bit IEEE floating-point format to the 32-bit IBM floating-point format are different in efficiency as well. In contrast with other programming language proposed by listed references with respect to the partial conversion of SEG-Y data format,we present a whole C language program for converting the SEG-Y data format correctly. Read,rewrite and store SEG-Y data correctly has been implemented in different CPU architecture of computer. Good portability of program guarantees the sharing and application of seismic data.