<head>
<meta name="GENERATOR" content="Adobe PageMill 3.0 Win">
<title>NASA Ames Format for Data Exchange - Welcome Page</title>
</head>
<body bgcolor="#ffffff">
<h1><font color="#333399">NASA Ames Format for Data Exchange</font></h1>
<hr>
<center>
<font size=-1>Quick links to</font>
<table cellpadding=8><tr><td align=center bgcolor=#0055aa>
<a href="FFI-summary.html"><b><font color=#ffffff>FFI Summary</font></b></a>
<br>
<b><font color=#ffffff size=-1>3 tables summarising the nine NASA Ames Format
styles and displaying all possible file headers.
</font></b>
</td></tr></table>
<table cellpadding=8><tr><td align=center bgcolor=#0055aa>
<a href="NASA-Ames-templates-1001-1020.xls"><b><font color=#ffffff>Annotated
Excel templates of FFIs 1001 and 1020</font></b></a>
<br>
<b><font color=#ffffff size=-1>Including examples and instructions on Excel to
NASA Ames conversion.
</font></b></td></tr></table>
</center>
<b>Note: The BADC recommends NASA-Ames format version 1.3.</b>
<h3>
Contents
</h3>
<ul>
<li><a href="#Eme">Emergence and general characteristics</a>
<li><a href="#Nat">NASA Ames Format: for which type of data?</a>
<li><a href="#Arc">Archive concept</a>
<li><a href="#Nam">File names</a>
<li><a href="#FFI">File format indices</a>
<li><a href="#Str">File structure</a>
<li><a href="#Fur">Further reading</a>
<li><a href="#Exa">Examples</a>
<li><a href="#For">Formatting your data</a>
<li><a href="#Che">Checking your data files</a>
<li><a href="#Upl">Uploading NASA Ames files to BADC</a>
<li><a href="#Rea">Reading and understanding NASA Ames formatted data</a>
</ul>
<h3><a name="Eme">Emergence and general characteristics</a></h3>
The NASA Ames Format for Data Exchange, often referred to as NASA Ames Format,
grew out of NASA aircraft campaigns and was first formalised at the Ames
Research Centre, California, during the 1987 Stratosphere Troposphere Exchange
Project (STEP), when uniform rules to record data were needed to <b>facilitate
the data exchange</b> between the participants and allow <b>shared use of a
minimised amount of software</b> to analyse and display different datasets.
The issue was that the adopted data format should meet the following
requirements:
<ul>
<li>it had to be <b>portable</b> (readable on any machine by any programming
language);
<li>it had to be <b>self-describing</b> (that is, the data had to include an
attachment containing all the information needed to read, understand and
interpret them – thus ensuring the reader's autonomy);
<li>it had to be <b>readable by humans</b> (to retain the benefit of its
self-description!).
</ul>
The first and third requirements implied the adoption of a text format (namely
<b>ASCII</b>).
The second condition was met by including in each data file a <b>header</b>
containing the descriptive information (<i>metadata</i>).
<p>
Very well suited to field campaigns involving several teams that need to share
their observations, the NASA Ames Format is not well adapted to very voluminous
datasets.
In this case, although less portable, a binary format is recommended.
</p>
<h3><a name="Nat">NASA Ames Format: for which type of data?</a></h3>
Any set of functions of 1 to 4 variables can be recorded using the NASA Ames
format, which makes it particularly suitable for atmospheric datasets, whether
modelled or observed.
Some NASA Ames file format indices (see below) are better adapted to airborne
platforms (balloons, aircraft).
<br><br>
The number of values taken by one (and only one) of the independent variables
is not defined <i>a priori</i> in the data file – so that the data provider
does not need to know in advance how many values it takes.
This single independent variable is called <i>unbounded</i>, although it is
bounded in a mathematical sense.
All other independent variables, if they exist, are <i>bounded</i>, meaning that
the number of values they take is explicitly defined in the data file –
and implying that the data provider has determined these numbers before
formatting the data.
<br><br>
The NASA Ames Format nomenclature distinguishes between
<table>
<tr valign=top>
<td width=12><img src="blue-dot.gif"></td>
<td>up to four <b>independent variables</b> (usually but <u>not
necessarily</u> time and/or space) – in most cases, real numbers,
one FFI allowing the use of one alphanumeric independent variable
(<i>i.e.</i> a piece of text);</td>
</tr>
<tr valign=top>
<td><img src="blue-dot.gif"></td>
<td>the <b>primary dependent variables</b> (functions of the former) –
real numbers;</td>
</tr>
<tr valign=top>
<td><img src="blue-dot.gif"></td>
<td>the <b>auxiliary dependent variables</b> (depending solely on the
<i>unbounded</i> independent variable) – real numbers or character
strings.</td>
</tr>
</table>
The fact that dependent variables are functions of the independent variables
implies that only one dependent variable value is associated to one given
set of values of the independent variables.
For real numbers, this means that the independent variable values can be
ordered in strictly increasing or decreasing order (the variable is
<i>monotonic</i>), which is indeed a requirement of the NASA Ames format.
There is always a way to order a finite number of objects, so that this is a
condition that can always be met (if necessary, by choosing an appropriate
independent variable such as a subset of the integers).
<br>
Except in a few instances, auxiliary variables are optional.
<h3><a name="Arc">Archive concept</a></h3>
<p>
The underlying philosophy is that data are stored in a file-based system, a
dataset being formed out of a series of numbered files.
Typically, files belonging to a same dataset share some common feature such
as the people who issued the data, the experiment, the platform,...
This, however, is not a requirement and it is up to the data provider to
organise the data files into datasets (possibilities ranging from one single
dataset including all files to one file per dataset).
The number of files of the dataset and the number of the file within the data
set are two elements of information that appear in the file header.
</p>
<h3><a name="Nam">File names</a></h3>
<p>
Whilst the first definitions of NASA Ames Format included rules regarding file
names, these have been dropped from most recent versions, that now allow any
naming convention or no convention at all.
File names and their extensions may of course include elements of information
on the data (<i>e.g.</i> site name, date, <i>etc</i>) or provide a way to
sort them out.
<br><br>
File name rules have been set up for specific NERC thematic programmes
Polluted Troposphere, UFAM, ACSOE, SOAPEX, UTLS-Ozone, URGENT.
</p>
<h3><a name="FFI">File format indices (FFI)</a></h3>
The NASA Ames Format is actually a set of nine formats that comply with an
overall common structure but make provision of different features adapted
to various cases (depending on the number of independent variables, whether
their values are regularly spaced out, <i>etc</i>).
To each of the nine formats is univokely associated a File Format Index (FFI),
which is a 4-digit number.
<h3><a name="Str">File structure</a></h3>
Each file is made of two parts.
At the top of the file, the file header includes information on the data
(metadata).
The actual data are recorded in the lines that follow the header.
In many cases, some of the independent variables are defined in the header and
are not repeated in the data section (<i>e.g.</i> for a regular grid).
An accurate description of each format is provided in the BADC <i>NASA Ames FFI
Summary</i> (see <a href="#For">Formatting your data</a>
below).
Here is a brief description of the contents of the two file sections.
<br><br>
<table>
<tr valign=top>
<td width=12><img src="blue-dot.gif"></td>
<td><b>Header</b> or <b>Metadata section</b><br>
The header includes, in a defined order and format, all the information
needed to read and understand the data. Namely:
<table>
<tr valign=top>
<td width=12><img src="green-dot.gif"></td>
<td>the number of the file within the dataset;
</td>
</tr>
<tr valign=top>
<td><img src="green-dot.gif"></td>
<td>the number of lines in the header;</td>
</tr>
<tr valign=top>
<td><img src="green-dot.gif"></td>
<td>the FFI (which unambiguously defines the structure of the data
section) and additional required information on the data format;
</td>
</tr>
<tr valign=top>
<td><img src="green-dot.gif"></td>
<td>the number, nature and <u>units</u> of all types of variables
(independent, primary and, when used, auxiliary), ordered as in the
data section;</td>
</tr>
<tr valign=top>
<td><img src="green-dot.gif"></td>
<td>information on the source of the data (name and affiliation of data
providers, experiment, instrumentation, model used, <i>etc</i>.);
</td>
</tr>
<tr valign=top>
<td><img src="green-dot.gif"></td>
<td>information on the data, data processing and data quality
(location, date, revision date, <i>etc</i>.).
</td>
</tr>
</table>
Comment fields are provided at the end of the header for any type of
additional information that would not fit in the predefined formatted
lines.
</td>
</tr>
<tr valign=top>
<td><img src="blue-dot.gif"></td>
<td><b>Data section</b><br>
The data proper are subdivided in a hierarchy of two-dimensional blocks,
the last independent variable (which is always the <i>unbounded</i>
variable – see <A HREF="#Nat">NASA Ames Format: for which type of data?</A> above)
being the most slowly varying one.
Note that error margins can be supplied as either primary or auxiliary
variables, if needed.
</tr>
</table>
<h3><a name="Exa">Examples</a></h3>
Each file format index is illustrated by one or several <a href="examples.html">examples</a>.
<h3><a name="Fur">Further reading</a></h3>
<a href="http://cedadocs.badc.rl.ac.uk/73/3/G-and-H-June-1998.html">Format Specification for Data Exchange, Version
1.3</a> (Gaines and Hipskind, 1998) is the primary reference for NASA Ames
formatting.
As far as possible, the BADC documentation keeps the same nomenclature and
notation system as in this original document.
<h3><a name="For">Formatting your data</a></h3>
<table>
<tr valign=top>
<td width=12><img src="blue-dot.gif"></td>
<td><a href="FFI-summary.html">NASA Ames FFI Summary</a> is a straightforward
instrument to identify the appropriate file format index and to format your
data step by step.
For each FFI, it includes links to detailed descriptions of the
corresponding data and metadata formats.
</td>
</tr>
<tr valign=top>
<td><img src="blue-dot.gif"></td>
<td><a href="makeheader.f">Makeheader.f</a>
is a self-explanatory Fortran program that generates NASA Ames file headers
tailored to the user's needs.
It does not require any knowledge of Fortran, only a Fortran compiler.
</td>
</tr>
<tr valign=top>
<td><img src="blue-dot.gif"></td>
<td>Many data files contain the variable <i>time</i> which can be expressed in
several ways.
<a href="nasa-ames-time.htm">Guidelines on the recommended format
of the time-variable header lines, units and the data values are available</a>.
</td>
</tr>
<tr valign=top>
<td><img src="blue-dot.gif"></td>
<td>The <font color=#ff0000><a href="NASA-Ames-templates-1001-1020.xls"><i>Excel</i>
templates of FFIs 1001 and 1020</a></font> (<i>Excel</i> format) also
include instructions on inserting metadata in NASA Ames files and
converting <i>Excel</i> spreadsheets to NASA Ames compliant ASCII files.
Two examples of spreadsheets are given for each FFI.
Their ASCII versions can be viewed here:
<ul>
<li><a href="./example-1001-a.na">Example 1001-a</a>.
<li><a href="./example-1001-b.na">Example 1001-b</a>.
<li><a href="./example-1020-a.na">Example 1020-a</a>.
<li><a href="./example-1020-b.na">Example 1020-b</a>.
</ul>
</td>
</tr>
<tr valign=top>
<td><img src="blue-dot.gif"></td>
<td><a href="na-for-dummies-1D.html">
Dummies Guide to NASA Ames format with 1D data</a></td>
</tr>
<tr valign=top>
<td><img src="blue-dot.gif"></td>
<td><a href="na-for-dummies-2D.html">
Dummies Guide to NASA Ames format with 2D data</a></td>
</tr>
<tr valign=top>
<td><img src="blue-dot.gif"></td>
<td>Specific additional rules apply to some NERC thematic programmes (ACSOE,
SOAPEX, UTLS-Ozone, URGENT, NEU).
Please refer to the Web pages of these data sets.
</td>
</tr>
</table>
<h3><a name="Che">Checking your data files</a></h3>
The <a href="http://badc.nerc.ac.uk/cgi-bin/dataex_file.cgi.pl">NASA Ames
Format checker</a> is an interactive facility provided by BADC, that allows you
to check your NASA Ames formatted files online.
It is based on a program written by S. Gaines, NASA Ames Research Center.
<h3><a name="Upl">Uploading NASA Ames files to BADC</a></h3>
For programmes currently submitting NASA Ames formatted files, the BADC provides
a Web based file uploader</a>.
In the process, files are checked for compliance with the NASA Ames standard.
<h3><a name="Rea">Reading and understanding NASA Ames formatted data</a></h3>
<table>
<tr valign=top>
<td width=12><img src="blue-dot.gif"></td>
<td>Every File Format Index is explained line by line in the
<a href="FFI-summary.html">NASA Ames FFI Summary</a> provided by BADC.
</td>
</tr>
<tr valign=top>
<td><img src="blue-dot.gif"></td>
<td>See also the source manual
<a href="http://cedadocs.badc.rl.ac.uk/73/3/G-and-H-June-1998.html">Gaines and Hipskind, 1998</a>.
</td>
</tr>
</table>
<p>
</body>
</html>