Malaysia: Nature gets a helping hand from sci-fi tech

Chai Mei Ling New Straits Times 31 Jul 11;

The aircraft glided across the skies over a vast expanse of forest, a sensor strapped to its underside capturing detailed and breathtaking shots, before this only seen in the realm of science fiction.

The hyperspectral imaging kit is able to identify individual trees, and amazingly -- after lab work -- zero in on the species.

Tree canopies will be bathed in a multitude of colours when scanned, as if buckets of paint had fallen off the sky and rained on the treetops.

In a population of mangroves, bakau minyak stands out in striking red, bakau kurap is swathed in turquoise, berembang purple, membuta emerald, piai pink, perepat yellow and gedabu bright green.

The rainbow of colours is a result of the vegetation's "varying reflectance", says Dr Alias Mohd Sood of Universiti Putra Malaysia (UPM).

When the sun shines upon objects, some of the rays are scattered and reflected.

This reflected energy is what's measured by the sensor, resulting in different colours, depending on the strength of the reflectance.

"In vegetation, chlorophyll absorbs red and blue lights but reflects green. That's why we see the leaf as green. That's the theory of light," says Alias.

While the human eye sees visible light in three bands, and satellite imaging captures eight, spectral imaging breaks down the electromagnetic spectrum into many, many more.

Up until two years ago, the airborne hyperspectral imaging system had over 200 bands, extending beyond the visible, which is why it could capture a colour and divide it into many more sub-colours.

When the sensor, attached to the belly of an aircraft, flies over forests, everything that makes up the texture of its canopy -- the combination of leaves, the shape of the leaf, the size, thickness, the branches, the subcanopy -- will be registered.

"Different plant species have different canopy textures, so they reflect light in their own way.

"That's why they appear in different colours in images," says Alias, a specialist in remote sensing, with a forestry background.

The system, put together by Professor Kamaruzaman Jusoff of UPM, was first used in the 1990s.

It detected cracks in boulders along the highway, surveyed forest reserves and mapped sedimentation in rivers.

After much fine-tuning by the forest engineering survey expert, the system was commercialised in 2004 through a joint venture between UPM and Aeroscan Precision (M) Sdn Bhd.

Among the company's earlier projects were mapping the Gunung Stong Forest Reserve in Kelantan, making an inventory of Kuala Lumpur's forested areas, and charting the coral distribution in Pulau Perhentian Kecil, Terengganu.

Then, two years ago, the company replaced the near-obsolete sensor with the latest technology -- one which comes with 488 bands at a cost of RM2.4 million.

The increased bandwidth propelled the potential of the kit's application to new areas.

The kit could now tell not just the tree condition, but also help zero in on the degree of its health, says Izani Ibrahim, chief operating officer of Aeroscan Precision.

This added edge is especially useful in the agriculture sector.

Healthy, stressed and dead trees can be revealed in a single imaging -- unhealthy trees have less chlorophyll, which in turn reflect less light. So, they register a weaker or duller colour.

"Imagine the time and manpower saved from reducing the need for plantation workers to go down to the ground and inspect each and every tree on hectares and hectares of land.

"If one-fifth or more of the tree is infected, there is no point saving it. Let it die. If the degree of infection is lower, treatment can still be carried out," says Izani.

Another useful function of the system is to identify nutrient level.

"In the oil palm business, fertiliser constitutes 50 to 60 per cent of the cost. If the tree health is already at an optimum level, there's no need for blanket application of fertiliser.

"If you're healthy, why take additional vitamins and supplements? This is precision agriculture -- applying the right amount of fertiliser to the right trees at the right time. And you save money," Izani adds.

Aside from species identification and mapping of tree height, diameter and tree crown feature, the imaging system is also able to capture tree stand count, forest health and density, timber volume estimation and vegetation index.

The kit also makes a better information-gathering tool in marine ecology, as it's able to perform ocean depth measurement and mappings of coral reef, water quality and beach infrastructure.

It can tell hard, soft and dead corals apart, the classification of coral genus and seaweed and seagrass distribution.

As the sole provider of hyperspectral imaging service in the country and the Southeast Asian region, Aeroscan Precision plans to expand its offerings overseas.

Its services has been sought by Arab countries to inventory their date plantations and map out tree health.

It is also working on sharpening the sensor's detection of valuable resources, such as minerals, gaharu in karas trees, and honeycombs on tualang trees.

Although the system is useful to detect illegal logging because it provides near real-time imagery, the noble intention of the practice is outweighed by the surging cost.

An area is surveyed only upon request because it is expensive to rent an aircraft, onto which the sensor is strapped.

Aircraft rental ranges from RM4,000 to RM4,500 an hour, and flights should only take place between 10am and 2pm -- the brightest hours of the day -- and only if the weather is good.

Rain, haze and a cloud cover of more than 20 per cent spell added cost, as the company still has to foot the aircraft rental bill despite not being able to fly.

Because of these limitations, hyperspectral imaging service does not come cheap. Aeroscan Precision charges RM30 to RM60 per hectare surveyed, an area of about 2.5 football fields.

Nevertheless, Izani stresses the importance of conservation.

The mapping of rare and endangered tree species is crucial so that the country is aware of the wealth of biodiversity that it has and can forge a better understanding on conservation methods.

Having an inventory of the distribution of corals will also encourage protection of the nation's marine ecosystem.