The vulnerability of Africa to the impact of climate change, which results in natural disasters and environmental degradation, accelerates hardship and poverty for millions of Africans. However, Africa still lacks the necessary scientific and technical capacity to assess fully and to monitor the possible future impacts of climate change. One of the instruments available to address the challenges of environmental monitoring (including climate change) and to provide early warnings of natural and human-made disasters for Africa's development is Earth observation satellites. Earth observation satellites record Earth's information from space and provide accurate, continuous, simultaneous measurements of our planet. The results of the application of Earth observation satellites have longterm social benefits which include the early detection of hurricanes and typhoons that can lead to prompt warnings for areas predicted to be affected, thus providing crucial time to implement safety measures to mitigate the effects of such disasters. Several authors concur with this position, stating that the global view from satellite observation is unmatched in its ability to capture the dynamics and variability of Earth processes. The capability to predict weather (among other things) has led Earth observation satellites to become essential to everyday applications that improve human safety and quality of life. However, despite the many benefits of the use of Earth observation satellites, it still remains a major challenge for Africa to explore the full potential of Earth observation satellites in addressing continental needs (Figure 1). 1 This commentary assesses the status of Africa in regard to Earth observation satellites. Nations which have had successful, independently launched satellites on indigenously developed launch vehicles Nations which have had unsuccessful, independently launched satellites on indigenously developed launch vehicles or have procured external launches for their satellites Nations which have used external resources for developing and launching their satellites Nations which have claimed to have successful, independently launched satellites on indigenously developed launch vehicles, but the claims have not been verified Source: Sharpe 1 Figure 1: The status of African space activities with regard to other countries Earth observation and space development in Africa African countries are currently participating in a variety of notable space technology initiatives. We have chosen, however, to focus on Africa's role in Earth observation. Africa is regarded as both a collector and a user of data for and from the Earth observation satellites. The notable leading African countries involved in Earth observation are South Africa, Egypt, Algeria and Nigeria. South Africa's history with space science is well documented. 2-6 The country's involvement in space science can be traced back to the 1950s to amateur rocket launch activities. Major activities in South Africa's participation in space science really expanded af...

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The appetite for up-to-date information about the earth’s surface is ever increasing, as such information provides a basis for a large number of applications. These include the earth’s resource detection and evaluation, land cover and land use change monitoring together with other vast environmental studies such as climate change assessment. Due to the advantages of repetitive data acquisition, the synoptic view, together with the varied spatial resolution it provides, and its available historically achieved dataset, remote sensing earth observation has become the major preferred data source for various earth studies. This study assesses land cover change detection of the land cover products (2013_2014 and 2017_2018) derived from earth observation.There are vast number of change detection methodologies and techniques with some still emerging. This study embarked on post classification change detection methodology which entailed morphological and spectral filtering techniques. The 10 land cover classes that were assessed for change detection are: natural wooded land, shrubland, grassland, waterbodies, wetlands, barren lands, cultivated, built-up, planted forest together with mines and quarries. The change detection accuracy result was 74.97%. Through the likelihood analysis, the likelihood for change to occur (e.g. cultivated to grassland) and unlikelihood of change to occur (e.g. built-up to planted forest), resulted in 72.2% areas of potential realistic change.The change detection results, further depend on the quality, compatibility and accuracy of the input land cover datasets. The application of different ancillary data together with different modelling techniques for land cover classification also affect the true reflectance of land cover change detection. Therefore extra caution should be exercised when analysing change detection so as to provide true and reliable changes.

This .study investigates the use of Remote Sensing technology for geological mapping in an area south of the Orange River near Alexander Bay in South Africa. Landsat, ASTER and Hymap images were used to discriminate geological lithologies and .stnictures in the study area. The results of the images were compared witli each other using the 1: 50 000 geological map as a reference.The Minimum Noise Fraction (MNF) was the remote sensing technique used to identify different lithological units in the study area. The MNF bands were displayed in an RGB band (colour) combination in order to enhance the lithologies identified in each image. The MNF 459, .S21, and 431 band combinations for Hymap. ASTER and Landsat images were used respectively. Hymap images were the most infoimative in lithological discrimination followed by ASTER and with Landsat being the least effective. The rock types of the Orange River Group (ba.saltic andésite and rhyolite) were clearly identified from the Vioolsdrif Suite rock types (granitoids) occurring in the study area by the Hymap image.Pixel size, spectral and spatial resolution differences of Hymap, ASTER and Landsat images were the result of discriminatory qualities of lithological information retrieved by the different sensors. Tlie co.st effectiveness of each image type in relation to the stutly area size is one of the major challenges in data selection and therefore should be considered in the initial planning stages of geological mapping. ,

This research focuses on the application of the Spectral Angle Mapper technique on hyperspectral HyMap airborne data and band ratios of ASTER satellite multispectral data together with aeromagnetic data for target area detection for porphyry copper exploration in the Namaqua Metamorphic Province. Improved spectral and spatial resolution of both aerial and satellite remote sensors made it possible to map the lithology and mineralogy in greater detail than in the past. This study pinpointed one location with a high potential for porphyry copper deposits, warranting detailed field verification. The field verification would include geochemical and laboratory analysis to study economic viability of the deposit. SOUTH AFRICAN JOURNAL OF GEOLOGY MULTISPECTRAL AND HYPERSPECTRAL REMOTE SENSING 260 Figure 1. The location and geological map (1:50 000) of the study area.