High Resolution Monitoring Systems

Radar imagery is superior to optical imagery for obtaining a timely cloud free overview of recent changes in forest areas.
The 1998 image above - a small subset of a beautiful JERS radar composite - shows pristine and logged-over peat swamp forest (logging rails visible). One of the few useful Landat scenes available - for 2001 - still suffers from cloud cover. The ASAR Wide Swath radar image of 2005 with only 75 meter resolution shows enough detail to detect changes such as a new road (linear feature on the left), deforestation before 2005 (dark green/blue), recent deforestation (red/yellow) and fire impact (red). MODIS fire hotspots of the same period nicely overlap with the latter. These changes are also depicted in pink on the 2005 Landsat (note the scanline errors resulting from satellite malfunction since 2003).

The high resolution system routinely generates detailed information on land cover and land cover change every 35 days. Such systematic monitoring is practically impossible using traditional sensors such as Landsat hampered by cloud cover and smoke. Radar however can see through clouds and smoke. Map updates can be generated frequently (every 35 days), thus allowing for fast detection of changes such as suspected illegal logging in support of forest law enforcement. Detection of other adverse conditions such as fire risk, active fires, and fire damage are other types of information generated.

Publication of results can be shown on the internet. This enables authorities and the general public at large to regularly follow the condition of production forest and protected areas. The detail offered using ERS and ASAR is convenient for change mapping in nature reserves, forest concession areas and agro-industrial plantations and surroundings. Relevant changes can be highlighted, such as changes in the forest canopy through logging or landslides, (illegal) clearing of areas (for agriculture, mining, oil palm plantation), expansion of road networks, fire impacts and vegetation development.

Pre processing
During the pre processing phase every new input (radar) remote sensing image is calibrated, precisely georeferenced to the same coordinates as previous images and carefully corrected for topographic influences. It is then added to a "stack" (pile) of all previous images.

Change detection
In the change detection process, the latest image is compared to previous images of the image stack. The radar signal of undisturbed forest remains fairly stable over time, allowing for changes to be distinguished. After taking natural variation into account, any significant changes are written to a raw change map.

Post processing
The raw change map/image is further processed to be adapted to the actual field circumstances and combined with other GIS layers.

Map making
The final step is the production of a user friendly map of the latest changes detected (see example map in Application fields below). This can be a hardcopy or digital map or an update of a dedicated webGIS front-end. Accurate coordinates are included to enable fast verification of change areas in the field by local users, for instance by means of cheap ultra-light aircraft or land-rover (in accessible areas).

Application fields

Support nature conservation
The system is perfectly suitable in support of local management and law enforcement in National Parks and Nature Reserves. The system can provide regular information on the location of changes within park and reserve borders and surroundings, such as changes in the forest canopy through logging or landslides, (illegal) clearing of areas (for agriculture, mining, oil palm plantation) and encroachment patterns, expansion of road networks, fire impacts and vegetation development.

In addition, based on the monitoring data, the existing condition of the land and vegetation (forest) cover can be mapped. Radar imagery can be interpreted to derive several types of vegetation and land use including natural forest (Dipterocarp forest and Heath forest), selective logging activity, secondary forest, plantation areas, agriculture and settlement areas. The combination with Landsat or ASTER imagery offers even more possibilities.

Support the plantation industry
The establishment and management of industrial timber, pulp and paper, oil palm, soy, and tea and coffee plantations has frequently been linked with illegal logging, deforestation, forest fires and conflict with local communities over land. Widespread plantation expansion represents an important threat to wildlife habitat. Rising concern of civil society that not all plantations are established and managed sustainably could present a risk to the industry if not addressed. Investors, producers and retailers increasingly recognise these concerns and have begun developing voluntary codes of conduct in several sectors.

SarVision is currently working with the industry to provide critical (spatial) information to effectively take up two main challenges:

• The sound selection of appropriate lands for establishing new plantations
• The monitoring of sustainable management of existing plantations

Our monitoring systems can provide regular information on the implementation of voluntary principles and criteria on a transparent basis, making it accountable to all stakeholders.

Support timber industry
Regular analysis of ERS and / or ASAR imagery could be applied for frequent localisation of forest activities and timely detection and identification of areas for fast response on the ground. However, forest areas are often very large and inaccessible or fragmented into a large number of areas, making them difficult to administer effectively. In many countries, there is a lack of personnel, infrastructure and equipment, hampering adequate policing and supervision of logging activities. What little is available may much more efficiently be put into action using up-to-date remotely sensed information.

Regular analysis of ERS and / or ASAR imagery makes effective tracing of development of major disturbances possible:

• location of new logging roads
• degree of change in canopy cover associated with logging
• settlement and agricultural expansion into forested areas
• mining operations
• fire susceptibility and fire damage

In addition, regrowth of forest can be observed in ERS images, which may be of importance to monitor forest rehabilitation obligations.

Examples

The Mawas peat swamp forest reserve in Central Kalimantan is being monitored by SarVision since 2002 using ERS radar data and ENVISAT ASAR imagery as of late 2003.