1. Background

The Republic of Indonesia is a country located in Southeast Asia and Oceania, and comprises 17,508 islands with the area of 1,919,440 square kilometers, about 6,000 of which are inhabited. They are scattered over both sides of equator. Lying along the equator, Indonesia has a tropical climate, with two distinct monsoonal wet and dry seasons. Temperature differs little throughout the year; the average daily temperature range in Jakarta, capital city, is 26–30oC, with high humidity with average of about 80%. With a population of 230 million people, it is the world’s fourth most populous country and has the world’s largest population of Muslims. Its average population density is 134 people per square kilometer, although Java, the world’s most populous island, has a population density of 940 people per square kilometer. About 60% of the total Indonesian population lives in Java whose area is about 10% of the whole land area, as can be seen on the map below. Many islands contain rugged mountains, dense jungles, swamps, and valleys. There are around 200 volcanoes, of which 60 are still active. Because of these geographical conditions there are many areas very difficult to reach.