The FreeForm Data Handler

Preface

This document describes the OPeNDAP FreeForm ND Data Handler, which can be used with the OPeNDAP data server. It is not a complete description of the FreeForm ND software. For that, please refer to the ND manual.

This document contains much material originally written at the National Oceanic and Atmospheric Administration's National Environmental Satellite, Data, and Information Service, which is part of the National Geophysical Data Center in Boulder, Colorado.

This document has been updated to include information on FreeForm ND, the last release of FreeForm. FreeForm is now supported only for use with the Distributed Oceanographic Data System; see the OPeNDAP for more information.

We are interested in your comments about the OPeNDAP software, and the FreeForm ND software and this document. Send them to: support@opendap.org.

Using FreeForm ND with OPeNDAP, a researcher can easily make his or her data available to the wider community of OPeNDAP users without having to convert that data into another data file format. This document presents the FreeForm ND software, and shows how to use it with the OPeNDAP server.

Tasks Illustrated in this Guide

For a quick start to getting, installing, and using the FreeForm ND software, see the list below of tasks described in this document.

• Quick start. (here)
• Getting and installing the FreeForm ND software. (here)
• Serving tabular data. (here)
• Array tabular data. (here)
• Dealing with data file headers (here)
• Setup of File servers (here)

Who is this Guide for?

This guide is for people who wish to use FreeForm ND to serve scientific datasets using the OPeNDAP software. Scientists who wish to share their data with colleagues may also find this a useful system, since it is a relatively simple matter to set up a server that can allow remote access to your data.

This documentation assumes that the readers are familiar with computers and the internet, but are not necessarily programmers. More than a passing familiarity with different data file formats will be useful, as will an understanding of elementary internet concepts, such as URLs and http.

This manual also assumes some familiarity with the OPeNDAP software. If you are starting from scratch, knowing nothing at all about OPeNDAP, we strongly encourage you to browse the The OPeNDAP User Guide before reading too far here.

Organization of this Document

This book contains both introductory and reference material. There is also a description of the installation procedure.

Chapter 1

: contains an overview of the OPeNDAP FreeForm ND Data Handler

software, including how to get it and install it.

Chapter 2

provides a brief introduction to writing

format descriptions and using the OPeNDAP FreeForm ND Data Handler.

Chapter 3

provides detailed information about

writing format descriptions to facilitate access to data in tabular formats.

Chapter 4

provides detailed information about

writing format descriptions to facilitate access to data in non-tabular (array) formats.

Chapter 5

tells you how to work with header

formats.

Chapter 6

describes the operation of the OPeNDAP FreeForm ND Data Handler, with tips for writing format files.

Chapter 7

Chapter 8

presents FreeForm ND file name

conventions, the search rules for locating format files, and standard command line arguments for FreeForm ND programs.

Chapter 9

shows you how to use the FreeForm ND

program newform to convert data from one format to another and also how to read the data in a binary file.

Chapter 10

discusses the FreeForm ND program

checkvar, which you can use to check data distribution and quality.

Chapter 11

\appref{ff,hdf}

provides explanations for a small selection

of tools that will be useful for programmers working with the HDF file format.

\appref{ff,errors}

presents a list of common FreeForm ND error

messages. These are the error messages that may be issued by the \ffnd utilities, such as newform, not the OPeNDAP FreeForm ND Data Handler.

A position box is often used in this book to indicate column position of field values in data files. It is shown at the beginning of a data list in the documentation, but does not appear in the data file itself. It looks something like this:

1         2         3         4         5         6
012345678901234567890123456789012345678901234567890