Welsh Researchers Turn to Satellite Technology to Build Wildlife Habitat Maps
[Satellite News 11-12-10] Satellite imagery is playing a new innovative role in the area of wildlife habitat surveys in Wales. The country is hoping to be the first in Europe to produce a national map of habitats using satellite technology through a project that will be completed in March 2012.
Professor Richard Lucas of Aberystwyth University’s Institute of Geography and Earth Sciences spoke to Satellite News about why Welsh academic and research organizations have turned to satellite technology.
Satellite News: How did the wildlife habitat survey project come about?
Lucas: The practical work started in the first part of this decade with a government project that was co-sponsored by the Countryside Council for Wales (CCW) and BNSC, which is now the U.K. Space Agency. This project focused on mapping wildlife and terrain under the Countryside and Rights of Way Act and exploited the capabilities of the image segmentation and classification software recognition.
Satellite News: What is the project’s initiative?
Lucas: This is a ‘bottom-up’ initiative in the sense that users are trying to create products and services that meet their needs, contrasting perhaps with the previous generation of ‘top-down’ initiatives from Global Monitoring for Environment and Security (GMES) program which has been focused around land cover/land use rather than habitats. The great opportunity is the meeting in the middle, where we can start to expect synoptic-scale products at a spatial and thematic resolution good enough to recognize objects and classes on the ground.
Satellite News: When did you start thinking about using satellite technology for this project?
Lucas: CCW and the other U.K. conservation agencies have always kept an eye on using optical satellite data for mapping habitats since the early days of Landsat MSS and ETM. The barrier has been: the lack of spatial resolution; the difficulty in obtaining a sufficient number of cloud-free scenes and the expense of both the imagery; and the analytical software and hardware. Agencies such as CCW have tended to rely on airborne remote sensing and air-photo interpretation for vegetation mapping and assessment, which is better matched to the scale of habitats than most optical satellite imagery. With the much greater availability of imagery at sub-30 meter resolution, cheap desktop computers and relatively cheap analytical packages, it was worth trying some practical work because, for the first, time satellite remote sensing might be affordable as routine operational methods and not just one-off research projects.
Satellite News: What do satellite technologies offer the project that you could not get elsewhere?
Lucas: Field survey is the traditional method of mapping habitats, often combined with the use of air photo interpretation. Field survey techniques have always allowed us to collect highly detailed information on the presence, distribution and condition of habitats. When combined with the use of GPS, a level of mapping can be delivered that provides excellent opportunities for monitoring and assessment over local areas and protected conservation sites.
When wide area coverage of mapping is required, this approach is very time consuming and costly. The alternatives, such as Earth observation-based approaches that can deliver comparable results, become very attractive. Satellite technology also can help us to map areas that are difficult and often dangerous for field teams to map.
Compared with air photos, optical instruments offer spectral consistency across very large areas, repeatability and the availability of data in the visible, NIR and SWIR bands. A major task was to pre-process data from a range of sensors acquired at different times of year such that these were comparable in units of surface reflectance. However, once this had been completed, the classification of habitats, which was undertaken within a rule-based system, was able to be achieved consistently across Wales.
Satellite News: Who do you purchase imagery from and what are the costs?
Lucas: Satellite companies that the project has purchased satellite data from include the NPA Group for Spot 5, and IRS data. Imagery from Aster and Landsat data also was acquired.
The costs of developing and delivery this type of project have reduced dramatically in the last few years due in part to improvements in hardware and software, but also in the knowledge required to assemble the expert systems that are required to produce mapping at this level of detail. Cost is now at a level where the production of this national map – based on satellite and airborne imagery, combined with ecological knowledge – will be less that 1/10th of the cost of reproducing it through a systematic field survey.
Satellite News: What is the significance for Wales to be the first country in Europe to use satellite imagery in this way?
Lucas: There is already some existing mapping of land cover-land use, but nothing that looks at detailed habitats. Almost all European mapping is either field-based or done through a combination of air photo interpretation and fieldwork. There have been excellent maps produced from high-spatial resolution satellite data for small areas from Ikonos and Quickbird, or for relatively large areas with only a limited number of classes. No-one else to our knowledge has mapped such very large areas to the level of habitat classes. This is of course a very rapidly developing area, so there may be other initiatives which no-one else yet knows about, but the statement seems justified for habitats and Wales as a country. The significance of the project is transferability and raising everyone’s sights over what can be achieved.
Satellite News: What is the next step for satellite technology’s role in wildlife research imagery?
Lucas: The next step is looking at change-detection and mapping of environmental goods and services. Change detection methods will be a combination of post-classification –comparing old and new maps – and image-image comparisons, and may call for us to take novel approaches when working in the frequency domain, using anomalous change-detection algorithms or focusing more on biophysical properties able to be retrieved from optical and/or radar data. We would like to get all-Wales LIDAR coverage to combine with the optical satellite data to start mapping habitat structure, and would be interested in any new satellite instruments providing high-spatial resolution SAR or LIDAR.