Digital elevation models (DEMs) are considered an imperative tool for many 3D visualization applications; however, for applications related to topography, they are exploited mostly as a basic source of information. In the study of landslide susceptibility mapping, parameters or landslide conditioning factors are deduced from the information related to DEMs, especially elevation. In this paper conditioning factors related with topography are analyzed and the impact of resolution and accuracy of DEMs on these factors is discussed. Previously conducted research on landslide susceptibility mapping using these factors or parameters through exploiting different methods or models in the last two decades is reviewed, and modern trends in this field are presented in a tabulated form. Two factors or parameters are proposed for inclusion in landslide inventory list as a conditioning factor and a risk assessment parameter for future studies.

Disasters, whether natural or man induced have increased during the last decades in frequency all over the globe threatening a huge population within varied backgrounds. Over the years, remote sensing technologies have been functional in various disasters such as droughts, earthquakes, tsunamis, cyclones, etc. Its large area coverage capacity and observation repeatability makes its application cost effective. This paper tries to give the fundamental contributions and role of geographic information systems and remote sensing in disaster management applications. As an overview, it examines some recent practical application in disaster events. It also tries to look at some measurement characteristics and systems that have been applied to some disaster events within the disaster management framework and technologies. These various techniques and roles of remote sensing and geographic information systems in urban disaster monitoring and controlling, extends to disaster risk management using some sensors and satellites of emerging technologies. This discussion summarises in a single paper some of the many current techniques remote sensing and GIS employ in urban disaster management. Lessons from events can be drawn and implemented in similar scenarios to save lives and property.

Lack of historical land cover and urban growth governance structure makes spatial planning within the economic capitals of developing countries difficult. Monitoring urban built-up growth with insitu methods is complicated. In this paper, long-term Landsat archive is utilised to map the built-up areas of Accra, the economic capital of Ghana, in Africa. Simple two band ratio and band combination is coupled with historic Google Earth imagery to monitor built-up dynamics from 1980-2017. A 10-year period was sub-divided into three parts each; early period, mid period and late periodfor analysis. Maximum Likelihood classifier was used for the classification within the ENVI environment. The results show 11.90% as the highest and 4.63% as the lowest built-up growth rates between 2001-2005 and 1996-2000 respectively. Annual loss of non-built-up areas was 1.31%, and 48.57% over the entire study period. Water bodies lost 0.08% annually but 3.1% over the 37-year period. Highest and lowest overall accuracy were 87.18% and 81.31% respectively, with an average kappa coefficient of 0.7618. Gain in the built-up area was 1676.69 km 2 but non-built up areas lost 1576.10 km 2 while water bodies lost 100.60 km 2 . Results will be of interest to spatial planners, policy makers and land administrators.

Satellite navigation and communications system can substantially be disturbed by ionospheric perturbations. Consequently, monitoring ionospheric anomalous has great significance. In this study, we focus on the short-term irregular disturbances through a strong thunderstorm in Wuhan City, Hubei, China by using ground-based GNSS observations from dense Continuously Operating Reference Stations (CORS) with a sampling rate of 1s. The total electron content (TEC) was used to find possible perturbations after biases have been calibrated for the derived TEC. Additionally, the geomagnetic conditions and the state of solar radiation was checked in the study period to recognize the causes for the ionospheric disturbances. The maxima and minima values of TEC deviations were ~2.5 and 0.5 TECU, respectively. Three methods of Detrended Fluctuations Analysis (DFA) were applied to assess the ionospheric disturbances over GNSS CORS stations; “Multi-step numerical difference”(MSND), “6th order polynomials fitting” (PF), and “one-week average difference”(AD). The analyzed results showed that MSND has the lowest performance. Meanwhile, the fitted TEC data with 6th order polynomials technique presented an improvement and a discrepancy related to MSND. To resolve this discrepancy, we proposed AD technique, it accomplished the best performance related to the TEC disturbances and was compared with the other two techniques. The research findings showed that ionospheric disturbed electrons can be generated with various rates and different velocities through lightning influences.

Decentralization problems in Africa have caused some infrastructure disparity between country capitals and distant districts. In Ghana, less public investment has created a gap between implementation results and theoretical benefits. Spectral indices are a good approach to extracting impervious surfaces, which is a good method of measuring urbanization. These are restricted by complexity, sensor limitation, threshold values, and high computational time. In this study, we measure the urbanization dynamics of Wa District in Ghana by applying a proposed method of impervious surface extraction index (ISEI), to evaluate the decentralization policy using Landsat images from 1984–2018 and a single S2A data. Comparing our proposed method with five other existing indexes, ISEI provided good discriminated results between target feature and background, with pixel values ranging between 0 and +1. Other indexes produced negative values. ISEI accuracy varied from 84.62–94.00% while existing indexes varied from 73.85–90.00%. Our results also showed increased impervious surface areas of 83.26 km2, which is about 7.72% of total area while the average annual urban growth was recorded as 4.42%. These figures proved that the quantification of decentralization is very positive. The study provides a foundation for urban environment research in the context of decentralization policy.

Besides OpenStreetMap (OSM), there are other local sources, such as open government data (OGD), that have the potential to enrich the modeling process with decision criteria that uniquely reflect some local patterns. However, both data are affected by uncertainty issues, which limits their usability. This work addresses the imprecisions on suitability layers generated from such data. The proposed method is founded on fuzzy logic theories. The model integrates OGD, OSM data and remote sensing products and generate reliable landfill suitability results. A comparison analysis demonstrates that the proposed method generates more accurate, representative and reliable suitability results than traditional methods. Furthermore, the method has facilitated the introduction of open government data for suitability studies, whose fusion improved estimations of population distribution and land-use mapping than solely relying on free remotely sensed images. The proposed method is applicable for preparing decision maps from open datasets that have undergone similar generalization procedures as the source of their uncertainty. The study provides evidence for the applicability of OGD and other related open data initiatives (ODIs) for land-use suitability studies, especially in developing countries.