Page 28 - MATLAB Recipes for Earth Sciences

2.5 Data Handling 19

2.4 Data Storage

This chapter is on how to store, import and export data with MATLAB. In
earth sciences, data are collected in a great variety of formats, which often
have to be converted before being analyzed with MATLAB. On the other
hand, the software provides a number of import routines to read many bi-
nary data formats in earth sciences, such as the formats used to store digital
elevation models and satellite date.
A computer generally stores data as binary digits or bits. A bit is similar
to a two-way switch with two states, on = 1 and off = 0. In order to store
more complex types of data, the bits are joined to larger groups, such as
bytes consisting of 8 bits. Such groups of bits are then used to encode data,
e.g., numbers or characters. Unfortunately, different computer systems and
software use different schemes for encoding data. For instance, the repre-
sentation of text using the widely-used text processing software Microsoft
Word is different from characters written in Word Perfect. Exchanging

binary data therefore is difficult if the various users use different computer
platforms and software. As soon as both partners of data exchange use
similar systems, binary data can be stored in relatively small fi les. The
transfer rate of binary data is generally faster compared to the exchange of
other fi le formats.
Various formats for exchanging data have been developed in the last
decades. The classic example for the establishment of a data format that
can be used on different computer platforms and software is the American
Standard Code for Information Interchange ASCII that was fi rst published
in 1963 by the American Standards Association (ASA). ASCII as a 7-bit
code consists of 27=128 characters (codes 0 to 127). Whereas ASCII-1963
was lacking lower-case letters, the update ASCII-1967, lower-case letters as
well as various control characters such as escape and line feed and various
symbols such as brackets and mathematical operators were also included.
Since then, a number of variants appeared in order to facilitate the exchange
of text written in non-English languages, such as the expanded ASCII con-
taining 255 codes, e.g., the Latin–1 encoding.

2.5 Data Handling

The simplest way to exchange data between a certain piece of software and
MATLAB is the ASCII format. Although the newer versions of MATLAB

provide various import routines for file types such as Microsoft Excel bina-