Executive Summary
Environment Systems were commissioned by the Scottish Government, working with the British National Space Centre ( BNSC) under the GIFTSS programme (Government Information from the Space Sector), to evaluate satellite earth observation as a cost-effective method of assessing the extent and severity of erosion in the upland organic soils of Scotland.
Soil is a non-renewable resource which performs many vital functions as part of the systems supporting food and other biomass production, storage, filtration and transformation of many substances including water, carbon and nitrogen. Peat soils are formed as a result of organic material that has accumulated over centuries. This build-up of organic deposits can be several metres in depth.
The spatial extent of exposed peat, intact peat, vegetated bog surfaces and pools is a highly important component in regards to the potential modelling of the carbon budget of peatland and global climate change. As long as a peat bog accumulates more organic matter than it loses, it functions as a carbon sink.
Previous attempts to map the distribution of upland peatlands have been reliant on aerial photography or satellite sensors (jointly known as 'earth observation') and have only attempted to answer first level ecological questions such as the extent of exposed peat. Advances in techniques and understanding of earth observation now allow for more detailed mapping and monitoring the surface of the Earth.
The GIFTSS study was set up to deliver an implementation test of mapping peat erosion using earth observation. The study was based on the Monadhliath Mountains which are located within the westernmost range of the Grampian Mountains in the highlands of Scotland.
For the study area SPOT5, IRS P6 and ASTER satellite imagery were prepared; including full geometric and atmospheric correction. Critical to the success of the project was the availability and full integration (into the automated processing chain) of current digital aerial photography. This image data was then complemented by GIS datasets that, whilst often historical and at differing scales and nomenclatures, provide a set of core topographic and thematic information.
The Definiens Developer object orientated rule-based classification software was successfully used to classify the imagery to produce a set of 'core level' data, which in turn was used to produce 'application level' data; in this case peat erosion maps. The advanced image segmentation (automated digitising) within Definiens provided the spatial framework for the classification, with a bespoke set of spectral and spatial rules driving the classification of the image segments. Overall map accuracy was calculated as over 84%, with clear visual coincidence between the classified map and both the in-situ field data and aerial imagery.
Indicative costs of implementing this method for Scotland have been provided to enable the costs and benefits of different approaches to soil monitoring to be evaluated.