This paper has stressed the importance of having a complete knowledge of your films, cameras, processing, and reproduction equipment. This knowledge, coupled with comprehensive, well documented quality control techniques, will produce information of immense value and of great significance to your country and its people.

If these recommendations go unheeded, the very opposite may result. Consider, for example, the improper use of a specialized film designed to detect a virus-type infection in a nation with a one-crop economy. The source and spread of the virus may go undetected until the entire nation is infected, and catastrophic economic conditions as well as great human suffering can result.

This hypothetical situation, of course, is an extreme case. I have asked my wife what she would think if her beloved Honduras lost an entire crop of bananas, rice, beans, or coffee to a virus or insect plague. Her reaction was one of horror and dismay for our friends and relatives in her native land.

The information presented in this tutorial paper is based on knowledge gained through the mistakes and successes of a quarter century in the profession. My first attempt at aerial remote sensing began with a $20 camera and a small piece of infrared film in a rented Piper Cub, trying to locate a geologic fault zone hidden under glacial debris since before man occupied North America. It was an unqualified success and enabled me to complete a university thesis. Recent assignments have dealt with highly sophisticated cameras being used by our astronauts to record geologic information on the far side of the moon.

The most important point I have tried to establish here is that only you and your scientists can determine the best system to accomplish your specific requirements. It was, I think, best said 2500 years ago by one of the most important human beings ever to inhabit our Earth:

"Believe nothing merely because you have been told it, or because it is traditional, or because you have imagined it. But whatsoever after due examination you find to be conducive to the good and to the welfare of all being—that doctrine believe and cling to it, and take it as your guide." The author was Gautama Buddha.