Geospatial Sciences & Technology
Permanent URI for this collection
Browse
Recent Submissions
Item An overview of the ORACLES (Observations of Aerosols above Clouds and their interactions) project: aerosol–cloud–radiation interactions in the southeast Atlantic basin(2020-06-14) Redemann, J ,; Wood, R; Zuidema, P; Doherty, S. J; Luna, B; LeBlanc, S E; Diamond, M S; Shinozuka, Y; Chang, I Y; Ueyama, R; Pfister, L; Ryoo, J.-M; Dobracki, A. N; da Silva, A M; Longo, K. M; Kacenelenbogen, M. S; Flynn, C. J; Pistone, K; Knox, N. M; Piketh, S. J; Haywood, J. M; Formenti, P.; Mallet, M; Stier, P; Ackerman, A S; Bauer, S.E; Fridlind, A.M; Carmichael, G. R; Saide, P. E; Ferrada, G. A; Howell, S. G; Freitag, S; Cairns, B; Holben, B. N; Knobelspiesse, K. D; Tanelli, S; L'Ecuyer, T. S; Dzambo, A. M; Sy, O.O; McFarquhar, G. M; Poellot, M. R; Gupta, S; O'Brien, J.R; Nenes, A; Kacarab, M; Wong, J. P. S.; Small-Griswold, J. D; Thornhill, K. L; Podolske, J. R; Schmidt, K.S; Pilewskie, P; Chen, H; Cochrane, S. P; Sedlacek, A. J; Lang, T. J; Stith, E; Segal-Rozenhaimer, M; Ferrare, R. A; Burton, S. P; Hostetler, C. A.; Diner, D. J; Seidel, F. C F. C.; Platnick, S. E; Myers, J. S; Meyer, K. G; Spangenberg, D.A; Maring, H; Gao, LSouthern Africa produces almost a third of the Earth's biomass burning (BB) aerosol particles, yet the fate of these particles and their influence on regional and global climate is poorly understood. ORACLES (ObseRvations of Aerosols above CLouds and their intEractionS) is a 5-year NASA EVS-2 (Earth Venture Suborbital-2) investigation with three intensive observation periods designed to study key atmospheric processes that determine the climate impacts of these aerosols. During the Southern Hemisphere winter and spring (June–October), aerosol particles reaching 3–5 km in altitude are transported westward over the southeast Atlantic, where they interact with one of the largest subtropical stratocumulus (Sc) cloud decks in the world. The representation of these interactions in climate models remains highly uncertain in part due to a scarcity of observational constraints on aerosol and cloud properties, as well as due to the parameterized treatment of physical processes. Three ORACLES deployments by the NASA P-3 aircraft in September 2016, August 2017, and October 2018 (totaling ∼350 science flight hours), augmented by the deployment of the NASA ER-2 aircraft for remote sensing in September 2016 (totaling ∼100 science flight hours), were intended to help fill this observational gap. ORACLES focuses on three fundamental science themes centered on the climate effects of African BB aerosols: (a) direct aerosol radiative effects, (b) effects of aerosol absorption on atmospheric circulation and clouds, and (c) aerosol–cloud microphysical interactions. This paper summarizes the ORACLES science objectives, describes the project implementation, provides an overview of the flights and measurements in each deployment, and highlights the integrative modeling efforts from cloud to global scales to address science objectives. Significant new findings on the vertical structure of BB aerosol physical and chemical properties, chemical aging, cloud condensation nuclei, rain and precipitation statistics, and aerosol indirect effects are emphasized, but their detailed descriptions are the subject of separate publications. The main purpose of this paper is to familiarize the broader scientific community with the ORACLES project and the dataset it produced.Item Use of TanDEM-X and Sentinel Products to Derive Gully Activity Maps in Kunene Region (Namibia) Based on Automatic Iterative Random Forest Approach(2021) Orti, Miguel Vallejo; Winiwarter, Lukas; Corral-Pazos-de-Provens, Eva; Williams, Jack G; Bubenzer, Olaf; Höfle, BernhardGullies are landforms with specific patterns of shape, topography, hydrology, vegetation, and soil characteristics. Remote sensing products (TanDEM-X, Sentinel-1, and Sentinel-2) serve as inputs into an iterative algorithm, initialized using a micromapping simulation as training data, to map gullies in the northwestern of Namibia. A Random Forest Classifier examines pixels with similar characteristics in a pool of unlabeled data, and gully objects are detected where high densities of gully pixels are enclosed by an alpha shape. Gully objects are used in subsequent iterations following a mechanism where the algorithm uses the most reliable pixels as gully training samples. The gully class continuously grows until an optimal scenario in terms of accuracy is achieved. Results are benchmarked with manually tagged gullies (initial gully labeled area <0.3% of the total study area) in two different watersheds (408 and 302 km2, respectively) yielding total accuracies of>98%, with 60% in the gully class, Cohen Kappa >0.5, Matthews Correlation Coefficient >0.5, and receiver operating characteristic Area Under the Curve >0.89. Hence, our method outlines gullies keeping low false-positive rates while the classification quality has a good balance for the two classes (gully/no gully). Results show the most significant gully descriptors as the high temporal radar signal coherence (22.4%) and the low temporal variability in Normalized Difference Vegetation Index (21.8%). This research builds on previous studies to face the challenge of identifying and outlining gully-affected areas with a shortage of training data using global datasets, which are then transferable to other large (semi-) arid regionsItem Use of TanDEM-X and Sentinel Products to Derive Gully Activity Maps in Kunene Region (Namibia) Based on Automatic Iterative Random Forest Approach(2020) Orti, Miguel Vallejor; Winiwarter, Lukas; Corral-Pazos-de-Provens, Eva; Williams, Jack G.; Bubenzer, Olaf; Höfle, BernhardGullies are landforms with specific patterns of shape,topography, hydrology, vegetation, and soil characteristics. Remote sensing products (TanDEM-X, Sentinel-1, and Sentinel-2) serve as inputs into aniterative algorithm, initialized using a micro mapping simulation as training data, to map gullies in the northwestern of Namibia. A Random Forest Classifier examines pixels with similar characteristics in a pool of unlabeled data, and gully objects are detected where high densities of gully pixels are enclosed by an alpha shape. Gully objects are used in subsequent iterations following a mechanism where the algorithm uses the most reliable pixels as gully training samples. The gully class continuously grows until an optimal scenario in terms of accuracy is achieved. Results are benchmarked with manually tagged gullies (initial gully labeled area <0.3% of the total study area) in two different watersheds (408 and 302 km2, respectively) yielding total accuracies of>98%, with 60% in the gully class, Cohen Kappa >0.5, Matthews Correlation Coefficient >0.5, and receiver operating characteristic Area Under the Curve >0.89. Hence, our method outlines gullies keeping low false-positive rates while the classification quality has a good balance for the two classes (gully/no gully). Results show the most significant gully descriptors as the high temporal radar signal coherence (22.4%) and the low temporal variability in Normalized Difference Vegetation Index (21.8%). This research builds on previous studies to face the challenge of identifying and outlining gully-affected areas with a shortage of training data using global datasets, which are then transferable to other large (semi-) arid regions.Item An analysis of the risk of collisions between aircraft and vultures in Namibia(Environmental Information Service and Namibia University of Science and Technology, 2020) Hauptfleisch, Morgan; Knox, Nichola; Heita, P; Aschenborn, Ortwin; MacKenzie., Monique LeaCollisions between aircraft and birds and other animals occur frequently and are known in the aviation industry as wildlife strikes. They are considered to be one of the most serious safety and financial risks to the global aviation industry. The International Civil Aviation Organisation, a United Nations specialised Agency, requires that the appropriate authority shall take action to eliminate or to prevent the establishment of any source which may attract wildlife to the aerodrome, or its vicinity, unless an appropriate wildlife assessment indicates that they are unlikely to create conditions conducive to a wildlife hazard problem. Namibian airports reduce the wildlife strike risk by managing the airport habitat and actively chasing birds and other hazardous animals away. The bird strike risk in airspace between airports is not managed or assessed in Namibia. Following one White-Backed Vulture strike and several reports of near-misses with vultures by pilots of small aircraft, this study investigated possible collision hotspot areas considering small commercial aircraft flight paths and vulture movement areas. The study used spatial proximity analysis and temporal overlap to compare telemetry and nesting location data for the three most commonly encountered vulture species to flight paths and times of small commercial aircraft. Collision risk hotspots were identified over three national parks: Etosha, Waterberg and the Pro-Namib portion of the Namib-Naukluft. Ascending from, or approaching, Hosea Kutako International Airport from the east was identified as a particular risk for White-backed Vulture conflict, while risk of Lappet-faced vulture strikes was high to the east of Walvis Bay airport. Flight times of vultures and aircraft corresponded greatly, increasing the collision risk. The recommendations of this work are that pilots of small commercial aircraft should be made aware of particular risk areas, and that landing at Hosea Kutako from the east, or taking off in an easterly direction should be minimised when wind conditions allow, to reduce vulture collision risk.Item Collaborative postgraduate programme in applied science in earth observation, Geographic Information Systems and Remote Sensing(Klaus Hess Publishers, 2018) Louw, Frikkie; Mwewa, Lameck; Maphanyane, Joyce; Sakala, Enock; Motola, SiddiqueCapacity-building in the Southern Africa Science Services Centre for Climate Change and Adaptive Land Management (SASSCAL) is an essential part of the initiative’s science programme. One of the major capacity limitations identifi ed at the Southern African Development Community (SADC) level is in the fi eld of Earth Observation, Geographic Information Systems, and Remote Sensing. Within Task 303, a collaborative Master of Science degree in Geographic Information Systems, Remote Sensing, and Earth Observation was designed and implemented by four SADC universities: University of Botswana (UB), University of Zambia (UNZA), Cape Peninsula University of Science and Technology (CPUT, SouthAfrica), and Namibia University of Science and Technology (NUST), the coordinating university.)Item An analysis of the risks collisions between aircraft and vultures in Namibia(Namibian Journal of Environment, 2020-05) Hauptfleisch, ML; Knox, Nichola; Aschenborn, O; MacKenzie, ML; Heita, PCollisions between aircraft and birds and other animals occur frequently and are known in the aviation industry as wildlife strikes. They are considered to be one of the most serious safety and financial risks to the global aviation industry. The International Civil Aviation Organisation, a United Nations specialised Agency, requires that the appropriate authority shall take action to eliminate or to prevent the establishment of any source which may attract wildlife to the aerodrome, or its vicinity, unless an appropriate wildlife assessment indicates that they are unlikely to create conditions conducive to a wildlife hazard problem. Namibian airports reduce the wildlife strike risk by managing the airport habitat and actively chasing birds and other hazardous animals away. The bird strike risk in airspace between airports is not managed or assessed in Namibia. Following one White-Backed Vulture strike and several reports of near-misses with vultures by pilots of small aircraft, this study investigated possible collision hotspot areas considering small commercial aircraft flight paths and vulture movement areas. The study used spatial proximity analysis and temporal overlap to compare telemetry and nesting location data for the three most commonly encountered vulture species to flight paths and times of small commercial aircraft. Collision risk hotspots were identified over three national parks: Etosha, Waterberg and the Pro-Namib portion of the Namib-Naukluft. Ascending from, or approaching, Hosea Kutako International Airport from the east was identified as a particular risk for White-backed Vulture conflict, while risk of Lappet-faced vulture strikes was high to the east of Walvis Bay airport. Flight times of vultures and aircraft corresponded greatly, increasing the collision risk. The recommendations of this work are that pilots of small commercial aircraft should be made aware of particular risk areas, and that landing at Hosea Kutako from the east, or taking off in an easterly direction should be minimised when wind conditions allow, to reduce vulture collision risk.Item Mapping and Monitoring Fractional Woody Vegetation Cover in the Arid Savannas of Namibia Using LiDAR Training Data, Machine Learning, and ALOS PALSAR Data(2019-11) Knox, Nichola; Wessels, Konrad; Mathieu, Renaud; Main, Russell; Naidoo, Laven; Steenkamp, KarenNamibia is a very arid country, which has experienced significant bush encroachment and associated decreased livestock productivity. Therefore, it is essential to monitor bush encroachment and widespread debushing activities, including selective bush thinning and complete bush clearing. The aim of study was to develop a system to map and monitor fractional woody cover (FWC) at national scales (50 m and 75 m resolution) using Synthetic Aperture Radar (SAR) satellite data (Advanced Land Observing Satellite (ALOS) Phased Arrayed L-band Synthetic Aperture Radar (PALSAR) global mosaics, 2009, 2010, 2015, 2016) and ancillary variables (mean annual precipitation—MAP, elevation), with machine learning models that were trained with diverse airborne Light Detection and Ranging (LiDAR) data sets (244,032 ha, 2008–2014). When only the SAR variables were used, an average R2 of 0.65 (RSME = 0.16) was attained. Adding either elevation or MAP, or both ancillary variables, increased the mean R2 to 0.75 (RSME = 0.13), and 0.79 (RSME = 0.12). The inclusion of MAP addressed the overestimation of FWC in very arid areas, but resulted in anomalies in the form of sharp gradients in FWC along a MAP contour which were most likely caused by to the geographic distribution of the LiDAR training data. Additional targeted LiDAR acquisitions could address this issue. This was the first attempt to produce SAR-derived FWC maps for Namibia and the maps contain substantially more detailed spatial information on woody vegetation structure than existing national maps. During the seven-year study period the Shrubland–Woodland Mosaic was the only vegetation structural class that exhibited a regional net gain in FWC of more than 0.2 across 9% (11,906 km2) of its area that may potentially be attributed to bush encroachment. FWC change maps provided regional insights and detailed local patterns related to debushing and regrowth that can inform national rangeland policies and debushing programs.Item Temporal statistical analysis and predictive modelling of drought and flood in Rundu–Namibia(Namibia University of Science and Technology, 2019-08) Orti, Miguel Vallejo; Negussie, KalebNamibia is a semi-arid country characterized by the alternation of long drought periods and short episodes of intense rain, which often causes great stress to plants, animals and people. Thus, a deep understanding of the spatio-temporal distribution of rainfall is required to minimize their negative impacts, affecting food security. The temporal occurrence of drought and rainy events in the North East of Namibia (Rundu area) is described and studied for a series of monthly rainfall from 1940 until 2015. Inter-arrival times analysis is conducted to model the occurrence of extreme (high and low) rainfall events through a Poisson Point Process (PPP). Adapting the definitions of drought and flood to the water demands of crops in Rundu, it is deduced that the average inter-arrival time for droughts is smaller than for rainy years, presenting 3 and 10 years respectively. Results of PPP are presented on Lorenz Curves for different study cases (more than one, two and three events per time unit). From the PPP results it can be extracted that the probability of suffering a drought in a period of 5 years in Rundu is approximately 70%, while this likelihood is only 40% for floods. Considering the occurrence of three or more events in a time period of 10 years, the probability is almost 50% for drought and less than 10% floods. Point Process (PP) analysis demonstrates that Poisson Distribution can be used to model the occurrence of drought and floods in Rundu area, being especially precise to model the presence of one event in periods between 1 and 10 years.Item Assessing Namibia’s performance two decades after independence. Part 2: Sectoral Analysis.(2011) Christiansen, T.This paper presents the results of a study which reviews Namibia’s performance over its two decades since independence. The study examines the achievements and shortcomings of the country in various fields: politics, civil society, economy, and social / socio-economic development. The results have been split into two separate but interconnected papers. This first article analyses Namibia’s situation at the dawn of independence, its external support by foreign countries and Namibia’s overall performance as compared to the neighbouring countries Angola, Botswana, South Africa, Zambia, and Zimbabwe. The present paper evaluates in particular data drawn from the World Bank Development Indicator Database and the 2010 Ibrahim-Index of African Governance. A subsequent second paper will present a more detailed appraisal of the above-mentioned development sectors.Item An Exploration of Participatory Mapping Approaches for Integrated Land Use Planning in the Hardap Region, Namibia.(2013) Mundia, L.C.The paper presents empirical findings on the potential value of participatory mapping for effective Integrated Land Use Plan (ILUP) by local communities in Hardap Region. It reflects on how future participatory approaches should be structured. The research applied a combination of approaches that include sketch mapping, photo-mapping and consultative meetings. Both positive and negative impacts of participatory mapping on ILUP were measured and local communities’ knowledge of participatory approaches objectively tested on the basis of this investigation’s findings. The research established that although participatory mapping is known to the experts in the fields of Geography, Geographical Information Systems (GIS) and Land Use Planning (LUP), it is still not well known to local land users whose knowledge of other participatory approaches that can support ILUP in Namibia is limited. Participatory maps that were produced by local communities in Hardap region suggest that local communities are willing to learn about participatory approaches and willing to share their knowledge on land use. Sketch and photo-maps - although not accurate and sometimes imprecise - were found to be satisfactory approaches to capture and document local knowledge. Local communities are motivated to improve their land use activities by the outcomes of their knowledge input in participatory mapping. Key recommendations include comprehensive participatory land use planning and better knowledge gathering from local communities. The paper presents results of participatory mapping and lessons learned from exploring participatory mapping.Item Remote sensing of forage nutrients: Combining ecological and spectral absorption feature data(Elsevier, 2012) Knox, N.M.; Skidmore, A.K.; Prins, H.H.T.; Heitkönig, I.M.A.; Slotow, R.; van der Waal, C.; de Boer, W.F.Forage quality in grassland-savanna ecosystems support high biomass of both wild ungulates and domestic livestock. Forage quality is however variable in both space and time. In this study findings from ecological and laboratory studies, focused on assessing forage quality, are combined to evaluate the feasibility of a remote sensing approach for predicting the spatial and temporal variations in forage quality. Spatially available ecological findings (ancillary data), and physically linked spectral data (absorption data) are evaluated in this study and combined to create models which predict forage quality (nitrogen, phosphorus and fibre concentrations) of grasses collected in the Kruger National Park, South Africa, and analysed in both dry and wet seasons. Models were developed using best subsets regression modelling. Ancillary data alone, could predict forage components, with a higher goodness of fit and predictive capability, than absorption data (Ancillary: R2 adj ¼ 0:42—0:74 compared with absorption: R2 adj ¼ 0:11—0:51, and lower RMSE values for each nutrient produced by the ancillary models). Plant species and soil classes were found to be ecological variables most frequently included in prediction models of ancillary data. Models in which both ancillary and absorption variables were included, had the highest predictive capabilities( R2adj ¼ 0:49—0:74 and lowest RMSE values) compared to models where data sources were derived from only one of the two groups. This research provides an important step in the process of creating biochemical models for mapping forage nutrients in savanna systems that can be generalised seasonally over large areas.Item Assessing Namibia’s performance two decades after independence.(2011) Christiansen, T.This paper presents the results of a study which reviews Namibia’s performance over its two decades since independence. The study examines the achievements and shortcomings of the country in various fields: politics, civil society, economy, and social / socio-economic development. The results have been split into two separate but interconnected papers. This first article analyses Namibia’s situation at the dawn of independence, its external support by foreign countries and Namibia’s overall performance as compared to the neighbouring countries Angola, Botswana, South Africa, Zambia, and Zimbabwe. The present paper evaluates in particular data drawn from the World Bank Development Indicator Database and the 2010 Ibrahim-Index of African Governance. A subsequent second paper will present a more detailed appraisal of the above-mentioned development sectorsItem Spatial diversity of dry savanna woodlands: Assessing the spatial diversity of a dry savanna woodland stand in northern Namibia using neighbourhood-based measures.(Kluwer Academic Publishers., 2004) Graz, F.P.The dry woodland savannas of Namibia are of significant socio-economic importance. The paper tests the suitability of a number of diversity indicators developed for species poor systems in Europe in the woodland context. The indicators that were tested included the species significant mingling index, MSp, the measure of surround and the uniform angle index. The simple application of the methods permit relatively unschooled crews to conduct an enumeration in the field. The results show that the indicators do not only display current diversity status, but also reflect the ecological context of the individual species.Item Comparison of Three Algorithms for the Evaluation of TanDEM-X Data for Gully Detection in Krumhuk Farm (Namibia)(2019) Vallejo Orti, M.; Negussie, K.; Corral-Pazos-de-Provens, E.; Höfle, B.; Bubenzer, O.Namibia is a dry and low populated country highly dependent on agriculture, with many areas experiencing land degradation accelerated by climate change. One of the most obvious and damaging manifestations of these degradation processes are gullies, which lead to great economic losses while accelerating desertification. The development of standardized methods to detect and monitor the evolution of gully-affected areas is crucial to plan prevention and remediation strategies. With the aim of developing solutions applicable at a regional or even national scale, fully automated satellite-based remote sensing methods are explored in this research. For this purpose, three different algorithms are applied to a Digital Elevation Model (DEM) generated from the TanDEM-X satellite mission to extract gullies from their geomorphological characteristics: (i) Inverted Morphological Reconstruction (IMR), (ii) Smoothing Moving Polynomial Fitting (SMPF) and (iii) Multi Profile Curvature Analysis (MPCA). These algorithms are adapted or newly developed to identify gullies at the pixel level (12 m) in our study site in the Krumhuk Farm. The results of the three methods are benchmarked with ground truth; specific scenarios are observed to better understand the performance of each method. Results show that MPCA is the most reliable method to identify gullies, achieving an overall accuracy of approximately 0.80 with values of Cohen Kappa close to 0.35. The performance of these parameters improves when detecting large gullies (>30 m width and >3 m depth) achieving Total Accuracies (TA) near to 0.90, Cohen Kappa above 0.5, and User Accuracy (UA) and Producer Accuracy (PA) over 0.50 for the gully class. Small gullies (<12 m wide and <2 m deep) are usually neglected in the classification results due to spatial resolution constraints within the input DEM. In addition, IMR generates accurate results for UA in the gully class (0.94). The MPCA method developed here is a promising tool for the identification of large gullies considering extensive study areas. Nevertheless, further development is needed to improve the accuracy of the algorithms, as well as to derive geomorphological gully parameters (e.g., perimeter and volume) instead of pixel-level classification.Item Woodland resources and management in southern Africa(2018) De Cauwer, V.; Knox, N.M.; Kobue-Lekalake, R.; Lepetu, J.P.; Matenanga, O.; Naidoo, S.; Nott, A.; Parduhn, D.; Sichone, P.; Tshwenyane, S.; Yeboah, E.; Revermann, R.The countries of southern Africa have an average forest cover of 32% with most forest situated in the tropics. These dry to moist forests are deciduous with a few evergreen species. The open canopy allows enough light to reach the ground to allow the development of a rich grass layer. Generally, these forests are referred to as woodlands. The article gives an overview of the Miombo, Baikiaea and Mopane woodlands of Angola, Zambia, Namibia, and Botswana and focuses on their composition, wood and non-wood resources. Plantation forestry is briefly discussed with most information from South Africa, which has the largest commercial forestry sector in the region. Threats to the southern African woodlands are highlighted, and the current status of woodland monitoring and management is summarised.Item Potential use of 3D-derived products generated from unmanned aerial vehicle (UAV) imagery for monitoring forest degradation and woodland structure changes in the Namibian dry woodlands(Klaus Hess Publishers, 2018) Knox, N.; Strohbach, B.J.; De Cauwer, V.Different remote sensing approaches (in terms of data and analysis) have been demonstrated to be efficient mechanisms for monitoring changes in woodland cover. The use of optical remote sensing in monitoring dry woodlands has proved challenging and resulted in underestimating the cover and distribution of open woodlands (Bastin et al., 2017). With the use of an integrated LiDAR and SAR approach, Mathieu et al. (2018) have demonstrated an effective means to assessing the distribution and fractional woody cover of savanna forests (including the dry woodlands of Namibia)Item Law Reform for Improved Delivery of Land to the Urban Poor(Ministry of Justice Law Reform and Development Commission, 2017) Zongwe, D.P.; Dausab, Y.The current formal land tenure system in Namibia is unable to effectively deal with the huge backlog in formalization of informal settlements, most of which are in the rural areas of Namibia. The system is considered too slow and expensive for this purpose, and is also perceived as only benefiting the rich, while being inaccessible and too expensive for the poor. The proposed Flexible Land Tenure System (FLTS) aims to resolve this problem by implementing cheaper forms of land tenure, and bringing cadastral services closer to the poor. The system offers security of title, but the titles have significant limitations compared to freehold. It is questionable whether the FLTS will significantly accelerate the delivery of land to the poor, and whether it will indeed achieve the aims of a pro-poor land tenure system. It might in fact burden the poor with an inferior land tenure system, thereby becoming an obstacle rather than an instrument for poverty reduction and economic development. The formal land tenure system, on the other hand, is in urgent need of reform. The development of the new Urban and Regional Planning Bill, Deeds Registries Act, Flexible Land Tenure Regulations, and the current review of land survey related regulations, present an opportunity to address this issue. The development of these acts and regulations should be approached in a holistic manner aimed at improving land delivery and administration in general, with specific focus on the needs of the urban poor. The aim should be to make the system accessible and beneficial to all classes of society, thereby eliminating the need for a parallel system for the poor.Item An overview of mesoscale aerosol processes, comparisons, and validation studies from DRAGON networks.(Copernicus Publications, 2018) Holben, B.N.; Kim, J.; Sano, I.; Mukai, S.; Eck, T.F.; Giles, D.M.; Schafer, J.S.; Sinyuk, A.; Slutsker, I.; Smirnov, A.; Sorokin, M.; Anderson, B.E.; Che, H.; Choi, M.; Crawford, J.H.; Ferrare, R.A.; Garay, M.J.; Jeong, U.; Kim, M.; Kim, W.; Knox, N.; Li, Z.; Lim, H.S.; Lui, Y.; Maring, H.; Nakata, M.; Pickering, K.E.; Piketh, S.; Redemann, J.; Reid, J.S.; Salinas, S.; Seo, S.; Tan, F.; Tripathi, S.N.; Toon, O.B.; Xiao, Q.: Over the past 24 years, the AErosol RObotic NETwork (AERONET) program has provided highly accurate remote-sensing characterization of aerosol optical and physical properties for an increasingly extensive geographic distribution including all continents and many oceanic island and coastal sites. The measurements and retrievals from the AERONET global network have addressed satellite and model validation needs very well, but there have been challenges in making comparisons to similar parameters from in situ surface and airborne measurements. Additionally, with improved spatial and temporal satellite remote sensing of aerosols, there is a need for higher spatial-resolution ground-based remote-sensing networks. An effort to address these needs resulted in a number of field campaign networks called Distributed Regional Aerosol Gridded Observation Networks (DRAGONs) that were designed to provide a database for in situ and remote-sensing comparison and analysis of local to mesoscale variability in aerosol properties. This paper describes the DRAGON deployments that will continue to contribute to the growing body of research related to meso- and microscale aerosol features and processes. The research presented in this special issue illustrates the diversity of topics that has resulted from the application of data from these networksItem The Cost of Land Registration: a Case Study of Cost Efficiency in Namibia.(International Institute of Geo-Information Science and Earth Observation (ITC), Enschede, Netherlands, 2003-06) De Vries, W.T.; Georgiadou, P.Y (Yola).; Lewis, J.In the light of the global discussion on reducing public and private expenditure on cadastral processes and services, this article reviews the transaction costs of land registration, based on data gathered in Namibia. The data show a large differentiation in the types of costs incurred in the process, as well as various levels of cost recovery. In addition, the degree to which delays in the operational registration processes influence the total cost to land developers and landowners is reviewed.Item Description and ecology of pterocarpus angolensis in Namibia.(NUST, 2004-05) Graz, F.P.The tree Pterocarpus angolensis is an important component of the dry woodland savanna of northern Namibia. Its timber provides the basic resource for much of the carvings in Namibia. Unfortunately little management, particularly regeneration, has been implemented in the country and current exploitation practices amount to mining of the species.