Applied Geomatics

The 20 m SPOT DEM (Digital Elevation Model) was acquired by the Office of the Surveyor-General of the Federation (OSGoF) in Nigeria for use in topographic mapping. A localized assessment of the DEM is needed to validate its stated accuracies as it is well-known that the vertical accuracies of global DEMs vary in different landscape contexts. Hence, this study assessed the quality of the DEM in various landscapes and terrain contexts by comparing its heights against 780 Ground Control Points (GCPs) in Lagos State and the Federal Capital Territory (FCT) of Nigeria. The pattern of distribution of the height differences was analyzed using spatial autocorrelation analysis, including other accuracy metrics employed. In the general accuracy assessment, the DEM yielded root mean square errors of 2.33 m in Lagos and 3.69 m in the FCT. It was shown that heights over the bare lands were the most accurately represented on the DEM while heights over built-up areas were the least accurate at both...

Historic gardens and their related landscapes are often experienced only for their social, aesthetic, and environmental resources, yet their cultural, architectural, and perceptive significance is often ignored. The paper demonstrates how historic and educational values of historic gardens and related landscapes can be revealed by combining historic maps, reading perspective cones, and also applying advanced digital and educational methods and techniques. Historical maps, especially military and cadastral maps, associated with historical iconography, can provide us with a lot of information to study historical gardens and also to define conservation and valorization plans that are related to the history of the site: geomatics tools to georeference and co-relate metric and non-metric historical maps provide growing useful outputs, that can be deployed through the use of Virtual Hubs, boosting the availability of content and the accessibility of open data for policy makers, experts, a...

The 20 m SPOT DEM (Digital Elevation Model) was acquired by the Office of the Surveyor-General of the Federation (OSGoF) in Nigeria for use in topographic mapping. A localized assessment of the DEM is needed to validate its stated accuracies as it is well-known that the vertical accuracies of global DEMs vary in different landscape contexts. Hence, this study assessed the quality of the DEM in various landscapes and terrain contexts by comparing its heights against 780 Ground Control Points (GCPs) in Lagos State and the Federal Capital Territory (FCT) of Nigeria. The pattern of distribution of the height differences was analyzed using spatial autocorrelation analysis, including other accuracy metrics employed. In the general accuracy assessment, the DEM yielded root mean square errors of 2.33 m in Lagos and 3.69 m in the FCT. It was shown that heights over the bare lands were the most accurately represented on the DEM while heights over built-up areas were the least accurate at both...

The 20 m SPOT DEM (Digital Elevation Model) was acquired by the Office of the Surveyor-General of the Federation (OSGoF) in Nigeria for use in topographic mapping. A localized assessment of the DEM is needed to validate its stated accuracies as it is well-known that the vertical accuracies of global DEMs vary in different landscape contexts. Hence, this study assessed the quality of the DEM in various landscapes and terrain contexts by comparing its heights against 780 Ground Control Points (GCPs) in Lagos State and the Federal Capital Territory (FCT) of Nigeria. The pattern of distribution of the height differences was analyzed using spatial autocorrelation analysis, including other accuracy metrics employed. In the general accuracy assessment, the DEM yielded root mean square errors of 2.33 m in Lagos and 3.69 m in the FCT. It was shown that heights over the bare lands were the most accurately represented on the DEM while heights over built-up areas were the least accurate at both locations. Despite this, the SPOT DEM accuracies in the varying land cover types surpassed its stated global accuracy. Also, Pearson’s correlation analysis revealed no indication that error distribution over the landscape was a function of slope and/or aspect. While the spatial distribution of height differences in Lagos State exhibited randomness, the trend in FCT manifested some spatial clustering. It is recommended that the country should extend the application scope of the DEM to exploit its utility to the maximum.

The documentation of heritage buildings is the preliminary action to deal with any problem related to the built heritage. The procedure of documentation requires a very diverse range of data (quantitative and qualitative) to be obtained and investigated in order to produce an accurate digital representation of the building. This type of work of data capture and interpretation is often conducted in isolation by different stakeholders and for a range of purposes, leading to a lack of communication between different data types, repeated effort and incomplete documentation. Heritage Building Information Modelling (H-BIM) is set to play a key role in the digital documentation of heritage buildings, as it can combine quantitative and qualitative data and facilitate the integration of different stakeholders and specialised data into the digital management of the different phases of dealing with heritage buildings. This paper aims to review the multitude of data types that could be included...

In recent times, there has been renewed interest in understanding the dynamics of land cover change and its relationship with several environmental parameters. This study assesses the interrelationship between land surface temperature (LST), normalized difference vegetation index (NDVI), normalized difference built-up index (NDBI), and land cover change in Amuwo-Odofin Local Government Area of Lagos State, Nigeria. Multi-temporal and multi-spectral Landsat imageries for years 2002, 2013, 2016, and 2019 served as the primary dataset. Using the parallelepiped classifier, the imageries were classified into five land cover classes-mixed vegetation, bare land, built-up area, water body, and wetland. The spectral indices (NDVI and NDBI) were computed and the LST was determined using a single-channel algorithm. Land cover transition matrices were calculated to examine the proportion of land cover change between classes, including the unchanged areas. Pearson's correlation analysis enabled an analysis of the interdependence or interrelationship in the distribution of the parameters. From 2002 to 2019, the highest land cover transitions recorded were bare land to built-up area (12.64 km 2), mixed vegetation to built-up area (21.55 km 2), wetland to mixed vegetation (8.87 km 2), and mixed vegetation to bare land (8.46 km 2). There was a negative correlation between LST and NDVI, and between NDVI and NDBI. The distribution of the LST, NDVI, and NDBI varied correspondingly in accordance with land cover changes. The increase in built-up area could be the major driver of the observed changes in LST, NDBI, and NDVI, with an observed relationship that NDBI and LST values increase with increase in built-up areas.

The 20 m SPOT DEM (Digital Elevation Model) was acquired by the Office of the Surveyor-General of the Federation (OSGoF) in Nigeria for use in topographic mapping. A localized assessment of the DEM is needed to validate its stated accuracies as it is well-known that the vertical accuracies of global DEMs vary in different landscape contexts. Hence, this study assessed the quality of the DEM in various landscapes and terrain contexts by comparing its heights against 780 Ground Control Points (GCPs) in Lagos State and the Federal Capital Territory (FCT) of Nigeria. The pattern of distribution of the height differences was analyzed using spatial autocorrelation analysis, including other accuracy metrics employed. In the general accuracy assessment, the DEM yielded root mean square errors of 2.33 m in Lagos and 3.69 m in the FCT. It was shown that heights over the bare lands were the most accurately represented on the DEM while heights over built-up areas were the least accurate at both locations. Despite this, the SPOT DEM accuracies in the varying land cover types surpassed its stated global accuracy. Also, Pearson’s correlation analysis revealed no indication that error distribution over the landscape was a function of slope and/or aspect. While the spatial distribution of height differences in Lagos State exhibited randomness, the trend in FCT manifested some spatial clustering. It is recommended that the country should extend the application scope of the DEM to exploit its utility to the maximum.

The paper investigates the issue of finite element model development for the structural assessment of existing structures on the basis of detailed (terrestrial laser scanning and image-based) point clouds to parametric models generated using HBIM (Heritage Building Information Modelling) technology. Different procedures and software combinations are investigated in order to provide useful hints trying to solve some of the criticalities which are still unsolved albeit the subject has been under investigation since some years now. It is worth noting that, when assets belonging to the cultural heritage domain (CH) are considered, the difficulties increase because of the peculiarity of the structural behaviour and often the singularity of the geometrical shape. The proposed methodology is presented considering the case of the “Paraboloide” of Casale (Italy), a construction from the early reinforced concrete age, which is now a relevant example of Italian concrete industrial heritage mai...

The 20 m SPOT DEM (Digital Elevation Model) was acquired by the Office of the Surveyor-General of the Federation (OSGoF) in Nigeria for use in topographic mapping. A localized assessment of the DEM is needed to validate its stated accuracies as it is well-known that the vertical accuracies of global DEMs vary in different landscape contexts. Hence, this study assessed the quality of the DEM in various landscapes and terrain contexts by comparing its heights against 780 Ground Control Points (GCPs) in Lagos State and the Federal Capital Territory (FCT) of Nigeria. The pattern of distribution of the height differences was analyzed using spatial autocorrelation analysis, including other accuracy metrics employed. In the general accuracy assessment, the DEM yielded root mean square errors of 2.33 m in Lagos and 3.69 m in the FCT. It was shown that heights over the bare lands were the most accurately represented on the DEM while heights over built-up areas were the least accurate at both...

Quick response in emergency situations is crucial, because any delay can result in dramatic consequences and potentially human losses. Therefore, many institutions/authorities are relying on development of strategies for emergency management, specially to have a quick response process using modern technologies like unmanned aerial vehicles. A key factor affecting this process is to have a quick geo-situation report of the emergency in real time, which reflects the current emergency situation and supports in right decision-making. Providing such geo-reports is still not an easy task because—in most cases—a priori known spatial data like map data (raster/vector) or geodatabases are outdated, and anyway would not provide an overview on the current situation. Therefore, this paper introduces a management methodology of spatial data focusing on enabling a free access and viewing the data of interest in real time and in situ to support emergency managers. The results of this work are twof...

The documentation of heritage buildings is the preliminary action to deal with any problem related to the built heritage. The procedure of documentation requires a very diverse range of data (quantitative and qualitative) to be obtained and investigated in order to produce an accurate digital representation of the building. This type of work of data capture and interpretation is often conducted in isolation by different stakeholders and for a range of purposes, leading to a lack of communication between different data types, repeated effort and incomplete documentation. Heritage Building Information Modelling (H-BIM) is set to play a key role in the digital documentation of heritage buildings, as it can combine quantitative and qualitative data and facilitate the integration of different stakeholders and specialised data into the digital management of the different phases of dealing with heritage buildings. This paper aims to review the multitude of data types that could be included...

Today, range cameras represent a cheap, intuitive and effective technology for collecting the 3D geometry of objects and environments automatically and practically in real time. Such features can make these sensors a valuable tool for documenting archaeological small finds, especially when not expert users are involved. Therefore, in this work, Scanner and itSeez3D, two of the most promising scanning applications actually available for the Structure Sensor, a range camera specifically designed for mobile devices, were tested in order to evaluate their accuracy in modelling the 3D geometry of two archaeological artefacts, characterized by different shape and dimensions. The 3D models obtained through the two scanning applications were thus compared with the reference ones generated with the more accurate photogrammetric technique. The results demonstrate that both the applications show the same level of geometric accuracy, which amounts generally to very few millimetres, from an overall point of view, and, at the same time, they substantially point out the good quality of the Structure Sensor 3D reconstruction technology. In particular, the itSeez3D application is surely the best solution for the color restitution, even if it requires a payment of $7 to export and thus to use effectively each model generated. On the other side, Scanner is a free application and its geometric accuracy is comparable to that of itSeez3D, but, however, the colours are frequently smoothed and sometimes not fully rendered.

This note presents the experimental results deriving from the application of two innovative photogrammetric techniques (with particular reference to non-conventional photogrammetric applications) for the production of time-space 3D models of the marine surface. Moreover, the first method (automatic three images processing (ATIP)) proposes some easy procedures to solve typical non-linear problems of analytical photogrammetry. In particular, once validated the technique of orientation of two images (two-step procedure based on two phases: relative orientation and absolute orientation, both characterized by non-linear functions), we propose a procedure for the automatic orientation of three images (the introduction of a third image allows avoiding human decision to find the final solution). The second method (Computer Vision Raspberry Pi—CVR) refers to the use of the “prompt” technique of computer vision (structure from motion) using five appropriately synchronized cameras to acquire simultaneously the various frames, thanks to the use of an acquisition system based on the use of Raspberry Pi. The experimentation was conducted both in the laboratory (on a model that allows to study a typical phenomenon of the Alpine Valtellina region, in the North of Italy) that directly at sea (on a portion of marine surface located in Reggio Calabria near the seafront). The results obtained show a substantial comparability of the results both between the two methods and with the actual data measured at sea with dedicated instrumentation.

Since many years, the GNSS has been regarded by the meteorological community as one of the systems for atmospheric water vapour remote sensing. Time series of wet delays, estimated as by-products of accurate positioning, have been assimilated into numerical weather prediction models. However, a dedicated use the system for water vapour monitoring is still under investigation. Ad hoc dense networks have been designed and implemented to collect data at a high spatial resolution, baseline lengths lower than 10 km, with the aim of describing the high spatial and temporal variability of tropospheric water vapour. Within this framework, the paper reports a study on how the positioning strategy affects the estimated coordinates and tropospheric parameters. The study was conducted on the data collected by an experimental network of geodetic receivers, used as single or dual frequency ones. More specifically, investigations were made on the use of L1-only or iono-free combinations in differential positioning of receivers 100 to 10 km apart, finding that L1-only data provide more accurate results. Therefore, comparisons between local coordinates and ZWD obtained from relative and absolute positioning were performed to provide the statistics of the differences; the agreement between the results for short baselines is always better than 1 cm standard deviation. In order to assess the differences in the results that can be obtained from the two strategies when applied to the same observation set, a further comparison was carried out in terms of baseline components and ZWD increments. It results that, even for dense networks, the differential approach produces accurate results without losing information compared to the absolute one.

There are several studies related to the cultural heritage digitization through HBIM (Heritage Building Information Modelling) techniques. Today, BIM (Building Information Modelling) software cannot represent old buildings with complex prominent and particularly detailed architecture perfectly, and multiple software are combined to obtain the buildings’ representation. In this paper, in order to find an alternative way of replicating the complex details present in antique buildings, a new methodology is presented. The methodology is based on a process of direct insertion of various 3D model parts (.obj), into a BIM environment. These 3D model elements, coming from the points cloud segmentation (from UAV and Laser Scanner), are transformed in intelligent objects and interconnected to form the smart model. The methodology allows to represent detail of the objects that make up an element of cultural heritage, although not standardizable in shape. Although this methodology allows to ens...

In this study, the impact of land use/land cover (LULC) change and climate variability on hydrological processes was assessed and simulated using the Soil and Water Assessment Tool (SWAT) in the Upper Brantas river basin, Indonesia. The Mann–Kendall (MK) test was used to analyze the spatial variations and temporal trends of the hydro-climatic variables in the basin. The model performance was assessed by using statistical indicators like coefficient of determination (R2), Nash–Sutcliffe model efficiency (NSE), the ratio of root mean square error to measured standard deviation (RSR), and percentage bias (PBIAS). These were found to be 0.905, 0.997, 0.061, and 5.7 during calibration and 0.916, 0.995, 0.071, and −6.967 during validation, respectively. During 1989–2006, LULC changes were found to be 26.12% forest, converted to 1.3% grassland, 0.03% water, 14.58% urban area, 6.77% mixed plants, and 3.44% rice fields. The integrated effects of the LULC change and climate variability decreased surface runoff, groundwater, lateral flow, and streamflow by −4.44, −2.27, −4.47, and −5.50%, respectively, but evapotranspiration (ET) increased to 0.63%. LULC change increased surface runoff by 20.14%, ET 0.03%, and streamflow 0.29%, but decreased in groundwater by −9.65% and lateral flow by −3.70%. The climate variability decreased surface runoff, groundwater, lateral flow, and streamflow by −19.07, −1.50, −0.53, and −5.78%, respectively. Both climate variability and LULC changes influence the hydrological processes. Therefore, this study recommends that the above two aspects should be taken into consideration for water resources planning and management in the study region in Indonesia.

The present study was carried out to identify the extent of flood hazard on the Fogera floodplain in the Ribb catchment of the Blue Nile River basin in Ethiopia. A coupled 1 dimensional (D) and 2D hydrodynamic model (i.e., MIKE FLOOD) was used to simulate the flood inundation extent and flooding depth under climate change scenario in the study area. MIKE FLOOD coupled with a SWAT was used to simulate the floods hazard maps under short-term (2030s) and long-term (the 2060s) future climate projections for the RCP4.5 scenario. The results were revealed that the future minimum and maximum temperature can be increased to 1.99 °C and 2.65 °C, respectively. The average annual rainfall can be increased in the future. The dimensionless inflow hydrograph was best fitted with Gumbel distribution for the 100 years return period. This was derived from an output of the hydrological model and then fed into MIKE FLOOD to generate the flood hazard maps. The intensity of annual floods was indicated an increasing trend under the RCP4.5 scenario. The model was calibrated using the historical hydro-meteorological data, measured River cross-section data, and Lake Tana water level. The result of flood frequency analysis showed that a flow value of 100 year return period can be expected to 290 m3/s, 346 m3/s, and 367 m3/s for historical, short-term, and long-term time periods, respectively. The prepared flood hazard map indicated that the flooded area can be expected to 57.72 km2, 59.3 km2, and 61.01 km2 for the base period, 2030s, and 2060s, respectively, while the depth of inundated flood flow in the study area may be anticipated to a depth of 4.23 m, 4.68 m, and 4.96 m for similar time periods, respectively. Therefore, this study will be helpful for the decision makers to take the decision about the planning for the flood mitigation measures in the study region.