Land Cover is the remotely observed biophysical cover of the earth’s surface, including vegetation, rock and human-modified surfaces such as buildings. This is different than Land Use, because a single land-cover type can be used in various ways by humans. Land use is a description of how people utilize the land and socio-economic activity - urban and agricultural land uses are two of the most commonly recognised high-level classes of use. www.eoearth.org definition
There is not a single approach to generate land cover & land use datasets and Infoterra RS experts emphasize on the spectral signature of the satellite image and the biophysical characterization that infers from it. The approach used is endorsed by the scientific community.
Infoterra’s method to map the Earth’s natural features and to carry out a standardised, high quality Land Cover project follows the steps below:
Land Cover steps
- Development of an agreed classification nomenclature through consultation with project partner (definition of the different classes,...)
- Selection of suitable satellite images from the time baseline onwards (for mapping changes, several years are necessary) and collection of reference data and/or use of field data from the project partner.
- Pre-processing of satellite images (ortho-rectification,...)
- Biophysical processing, i.e. processing the image to produce an absolute, physical description of the image in terms of pixel nature (vegetation, soil, ..) and attached physical characteristics. This is achieved by the so-called biophysical processing implemented in the Overland software. The output information layers are further named "biophysical layers".
- Classification using processes and algorithms under the operator’s control, i.e. the qualification of the "physical state" of each image object. The physical characterization obtained at pixel level from the biophysical layers must be supplemented by other features such as object texture or heterogeneity. A list of the accessible physical states, with attached criteria, is established and all image objects are classified according to this physical state nomenclature.
- On some cases an operation of image segmentation is necessary to produce "image objects" having manageable size and homogeneous features. Object rules can be applied at this stage.
- Quality control to check the overall quality level of the land use, land cover map.
