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Seen from Space 2008

"Island of the Gods"–Bali, Indonesia

 
Fig. 1. Mosaic (composite) Image of Bali
Bali Island (kmz, 2.57MB, Low Resolution) as seen on Google Earth.
Bali is a 140km-long, 80km-wide island located at the westernmost end of Lesser Sunda Islands in the southern part of Indonesia. It is located between Java on the west and Lombok on the east, is 5,500km2 in area, and has a population of about 3 million. Major cities are the port town Singaradja on the north and the state capital Denpasar on the south. Bali is the only non-Islamic-influenced island in Indonesia. Their religious affiliation is Balinese Hinduism, which combines existing Polynesian religious ritual and Hindu. Bali is known as the "Island of the Gods" due to the thousands of temples on the island. As it is located from 8° to 9° south latitude in the tropical zone, the island is prone to clouds, and the seasonal difference between the rainy season and the dry season is quite large.

Figure 1 is composed of the three images with the least cloud cover so far observed by ALOS Daichi. Green in the three images has been adjusted so that the differences should be minimal. However, adjoining parts look somewhat unnatural due to the differences of cloud cover and the seasonal state of the plants that cover the surface. Nevertheless, deep green mountains in the west are clearly visible. Bali Barat National Park on the west side of the island is a wildlife reserve where Bali’s endemic white bird, Jalak Putih (Bali Starling), is carefully protected. In the east of the island, Mt. Agung (3,142m), the highest peak of the island, and Mt. Batur (1,717m) covered with a dark-brown exposed lava field are visible.

Fig. 2. Mosaic (composite) Image of Bali captured by PALSAR
Figure 2 is composed from three images captured by the synthetic aperture radar (PALSAR) aboard Daichi. Since radar pulses penetrate clouds and the images were acquired almost in the same season, adjoining parts look natural and the island’s geographical features are quite recognizable. Brightness of this black and white image indicates the intensity of the microwave pulses emitted from the satellite toward the ground and reflected back to the satellite. Generally speaking, reflections from ground objects that face the satellite appear stronger. Since the three images were acquired from the northbound orbit, the western slopes of the mountains look brighter. Figure 2 clearly depicts the mountains dividing the island east and west.
Although there are some lakes near Mt. Batukau (2,276m) and other mountains in the center of the island, the rain brought by the north wind falls at the mountains and mostly flows northward, which makes the south side of the island a dry desert. It is said that people dug tunnels so water could flow from the lake to the south and turned the entire south of the island into sylvan land.
Smooth water surfaces or flat ground objects, such as the sea, lakes, or airport runways, do not reflect much of the signal back to the satellite and so look darker. Urban areas in Singaradja and Denpasar are also bright, indicating that buildings reflect radar signals quite strongly. Resort areas facing Kuta Bay and on the east of Badung Peninsula also look white.
Mt. Agung erupted in 1963, but the Mother Temple of Besakih, located on the southwest foot of the mountain and the head temple of Balinese Hinduism (Agma Hindu Dharma in Bali), is always crowded with worshippers. To its northwest, Mt. Batur, which erupted in 1917 and 1926, and the caldera Lake Batur are visible. Other caldera lakes seen further west are, from east, Lake Bratan, Lake Buyan, and Lake Tamblingan. From there, many valleys run down the slope toward the south and extend to the farmlands on the alluvial plain where Denpasar is located. The many black dots scattered over the plain are thought to be water-laden paddies. These paddies are also visible in Negara district southwest of the island.

Fig. 3. Close-up of Denpasar and Vicinity
Figure 3 presents a close-up image of Denpasar and its vicinity. Ubud area is located in the upper part of the image among dotted clouds. Ubud is known as a relaxing green area where visitors can enjoy many interesting spots such as temples and ruins in the mountains, an art museum, and the beauties of nature. Many stripes of different colors scattered among the dark green area indicate farmland with crops (light green), bare farmland (brownish-red), and roofs of settlements (light brown).
The urban area of Denpasar is located south of Ubud. This area is the political and economical center of Bali where government and companies maintain their offices.
To the south of Denpasar, Ngurah Rai International Airport lies in the narrowly pinched portion of Badung Peninsula. In the resort area to the north of the airport (white area in Fig. 2), shops and hotels cluster and look grey or brownish-red. They are, from south, Kuta, Legian, and Semynyak. Kuta and Legian are the most crowded beach resorts in Bali. These were peaceful fishing villages before many surfers from Australia and Europe came from the 1960s. The sleepy villages rapidly developed since then and are now crowded with young people day and night. In contrast, Semynyak gives the impression of a quiet and fashionable town. Many foreign residents settled there and started businesses of shopping, restaurants, spas, and boutique villas. Tanjung Benoa area to the north of Nusa Dua and southeast of the airport is an exclusive beach resort developed in a government-led plan from the 1970s. Only roads can be seen in the light-brown area south of the peninsula, which is due to be developed in the future.
Udayana University Jimbaran Campus is located about 5km south of the airport but unfortunately it is hidden below the white cloud. The Center for Remote Sensing and Ocean Science of Udayana University (UNUD/CReSOS), established in 2003, participates in the "Pilot Project on Utilization of ALOS Data in Indonesia" based on an agreement between JAXA and the National Institute of Aeronautics and Space (LAPAN) and conducts application research for the coastal zones of Indonesia.



Explanation of the Images:


(Click the images twice to enlarge.)
Satellite: Advanced Land-Observing Satellite (ALOS) (Daichi)
Sensor: Advanced Visible and Near Infrared Radiometer-2 (AVNIR-2) (Figs. 1 and 3) and Phased Array type L-band Synthetic Aperture Radar (PALSAR) (Fig. 2)
Date: (AVNIR-2)
0246 (UTC) on May 2, 2007 (Left image of Fig. 1)
0244 (UTC) on November 28, 2006 (Center image of Figs. 1 and 3)
0242 (UTC) on March 29, 2007 (Right image of Fig. 1)
(PALSAR)
1515 (UTC) on August 12, 2007 (Left image of Fig. 2)
1513 (UTC) on June 10, 2007 (Center image of Fig. 2)
1511 (UTC) on July 9, 2007 (Right image of Fig. 2)
Ground resolution: 10m (AVNIR-2) and 50m (PALSAR)
Map Projection: Universal Transversal Mercator (UTM)
Figs. 1 and 3
AVNIR-2 has four observation bands. The composite images are usually produced by assigning red to Band 3 (610 to 690nm), green to Band 2 (520 to 600nm), and blue to Band 1 (420 to 500nm). The resulting images have natural coloring as if seen by the naked eye. Thus, the following colors designate ground objects.

Green: Forests
Light green: Grass fields or farmlands
Grey or reddish brown: City area or roads
Flesh color: Harvested fields or bare land
Blue: Water surfaces
White: Clouds

Fig. 2
PALSAR is an active microwave sensor using L-band frequency to achieve cloud-free and day-and-night land observation. It is equipped with a radar beam pointing function across the ALOS flight direction and a ScanSAR function to provide a much wider area of observation. PALSAR was jointly developed by the Japan Aerospace Exploration Agency (JAXA) and the Ministry of Economy, Trade Industry (METI)/Japan Resources Observation System and Space Utilization Organization (JAROS).

Related Sites:
ALOS Research and Application Page
ALOS (Daichi) observes Earthquake-Stricken Area in central Java, Indonesia
JERS-1 SAR mosaic covering Insular South-East Asia
Land, Seen from Space
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