Multi-temporal Image Data Research Articles

Comparison of relative radiometric normalization techniques

Relative radiometric normalization (RRN) is a procedure used to prepare multitemporal image data sets for the detection of spectral changes associated with phenomena such as land cover change. This procedure reduces the numeric differences between two images that have been induced by disparities in the acquisition conditions (e.g. sensor performance, solar irradiance, atmospheric effects) rather than changes in surface reflectance. We have applied seven empirical multitemporal radiometric normalization techniques to 1973 and 1990 Landsat MSS images acquired of the Washington D.C. area. The results from the various techniques have been compared both visually and using a measure of the fit based on standard error statistic. Both methods of comparison indicate that a linear regression technique using pixels from the two images which did not undergo spectral change produces the best results.

Possibility of extraction of relative terrain heights from space images by a radiometric method

Abstract The paper describes a possibility to extract relative terrain heights by a radiometric method from Landsat MSS data. The proposed radiometric method to extract relative terrain heights is based on determination of a surface normal vector at a terrain point from multitemporal image data under an assumption of a certain spatial reflectance model. Spatial characteristics of reflectance of two types of forests covered with deciduous and coniferous trees in the mountainous test area were investigated in reference with digital elevation data and Landsat MSS images under five different conditions of solar illumination. The proposed radiometric method assuming Lambertian surface were applied to multitemporal Landsat MSS band 7 images in the test area to extract relative terrain profiles. The results show the potential of extraction of relative terrain heights from multitemporal space images by the proposed radiometric method in an area with homogeneous land cover.

Drought-related changes to geomorphologic processes in central Mali

Geomorphologic evidence exists for repetitive drought conditions in the African Sahel; within this framework of broad climatic changes through time, the 1968- 1985 drought episodes are not abnormal. The impact of recent drought on the economies and environments of Sahelian nations has been substantial, however, and the recovery capabilities off severely damaged lands are not well known. Study of the geomorphology and surface processes across a portion of Mali provides some constraints on the responses of desert fringe fluvial systems to changing environmental conditions. Multi-temporal orbital image data were used in combination with field investigation to map drought-affected soils, and to document changes to both fluvial and aeolian processes across the region of study. A combination of statistical methods yields consistent evidence of net albedo increases associated with particular landforms and surface processes over a nine-year interval. Although aeolian processes are a significant transport mechanism for removal and redistribution of soil materials, both orbital data and field study indicate that fluvial erosion is responsible for much of the primary topsoil loss and landform modification in this portion of the Sahel.

Thematic mapping from multitemporal image data using the principal components transformation

The principal components transformation is used to highlight regions of localized change evident in satellite multispectral imagery associated with bushfire damage and with vegetation regrowth following fire burns. In line with previous studies by other investigators it is the higher order components that are seen to lead to change enhancement. These components are classified by unsupervised techniques to yield thematic maps on which change classes are recorded. In this manner, confusion of class signatures between dynamic and static cover types is avoided. In the present case this relates to confusion between fire burn regions and water edge mixed pixels.