As heads of state and other government leaders enter the final rounds of the COP-15 climate change talks, many key issues remain unresolved. The target rate of emissions reductions by wealthy nations, the amount of aid to poor nations, and monitoring compliance are at the crux of the slow-moving negotiations.

It’s the monitoring piece where geospatial comes into play. As addressed in our last entry about the REDD initiative, several remote sensing methodologies can contribute to large-area forest carbon measurement and monitoring, each with unique benefits. This week we are taking a closer look, reviewing the top-three technologies and briefly exploring their strengths and weaknesses:

Optical imaging: Offering low-cost, repeat coverage acquisition over large project areas, satellite-based hyperspectral and multispectral imagery has shown some potential for biomass estimation. Systems with sophisticated scheduling enable around 70 percent cloud-free coverage in equatorial regions, thereby reducing weather obstacles. And while satellite is proving a good source for monitoring REDD sites in Brazil, it alone isn’t a good source for carbon measurement. For that, you need tree height data and optical imagery provides only canopy-level information.

LiDAR mapping: Foresters have long used LiDAR systems to measure forest canopy and vertical structures. As an active sensor, airborne LiDAR data can be acquired night or day, providing very dense and accurate datasets. The downside to this approach is the high cost of acquisition and processing over large areas. Satellite-based LiDAR systems may help control these costs with wide area coverage and automated processing capabilities. The Geoscience Laser Altimeter System (GLAS) on NASA’s Ice, Cloud, and Land Elevation Satellite (ICESat) is one such example. Some studies show promising results, though clouds are an issue, and so is a general lack of ground height data. So, again, LiDAR may be a technology best suited for monitoring practices.

IFSAR mapping: Low frequency, long bandwidth IFSAR is an all-weather technology that provides high foliage penetration for near bare-earth elevation data, even in dense forests. When combined with higher frequency, short bandwidth IFSAR (which provides elevations of top surfaces), it is possible to detect the heights of individual trees within a forest. That’s the beauty of GeoSAR; it offers both views of the forest simultaneously and can also be used to identify forest type. This data, combined with biomass information on individual tree species, enables efficient and accurate forest carbon content estimations.

But GeoSAR isn’t a silver bullet. Given the relative high cost of airborne acquisitions in comparison to satellite sensors, IFSAR isn’t an ideal monitoring solution. It’s role is to provide accurate baseline information from which REDD programs can be evaluated.

Fugro EarthData published an article about using dual-band IFSAR for carbon accounting in the July issue of PE&RS. It’s a good source of information about remote sensing and climate change monitoring. And, if you want to catch the latest on COP-15, here’s a live web cast of the proceedings.

Next week: COP-15 wrap-up and its implications for remote sensing. Check back then!