Showing papers in "Applied Geomatics in 2010"

Reality-based 3D documentation of natural and cultural heritage sites—techniques, problems, and examples

Abstract: The importance of cultural and natural heritage documentation is well recognized at international level, and there is an increasing pressure to document and preserve heritage also digitally. The continuous development of new sensors, data capture methodologies, and multi-resolution 3D representations and the improvement of existing ones can contribute significantly to the 3D documentation, conservation, and digital presentation of heritages and to the growth of the research in this field. The article reviews some important documentation requirements and specifications, the actual 3D surveying and modeling techniques and methodologies with their limitations and potentialities as well some visualization issues involved in the heritage field. Some examples of world heritage sites 3D documentation are reported and discussed.

Application of remote sensing and GIS in the study of environmental sensitivity to desertification: a case study in Basrah Province, southern part of Iraq

Abstract: This research utilizes the integrated remote sensing and geographic information systems (GIS) in the southern part of Iraq (Basrah Province was taken as a case) to assess the environmentally sensitivity area to desertification. The thematic layers of soil, vegetation, climate, and extent of sand movement are the main data required for estimating the desertification sensitivity index. These layers were extracted and manipulated from the available topographic map data, geologic map, satellite image (TM in 1990 and ETM+ in 2003), and field survey data analyses. Spatial analyst function in ArcGIS 9.3 software was used for matching the thematic layers and assessing the desertification index. The obtained data on change detection reveal that the area of active sand movement has increased from 4,118.3 to 4,558.1 km2, and the highly sensitive areas for sandy desertification are located in the western–southern parts of Basrah Province, representing 61.9% of the area belonging to class 5. The rest of the southern parts of the study location exhibit moderately sensitive areas for desertification, representing 18.9% of the total area belonging to class 4. The northern parts of the study location are characterized by a very low and low sensitivity for desertification, representing 8.5% and 10.7% of the total area, respectively. It is recommended that there is a need to establish a professional arid environment center, which can be coordinated with government sectors and different universities in southern part of Iraq to solve various environmental problems.

Mapping tropical forest cover and deforestation using synthetic aperture radar (SAR) images

Abstract: The changes in forest cover in many parts of the world lead to increase the accumulation of atmospheric carbon and thus accelerate the process of global warming. Optical remote sensing has been used to map and quantify deforestation but its application is limited because of the presence of cloud coverage on the images. Recent availability of several space-borne synthetic aperture radar (SAR) missions has widened the scope of utilizing radar images for monitoring of forest cover change. The objective of this investigation is to examine the capability of SAR data to assess and map deforestation. The study area is located at the tropical forest region of southeastern Bangladesh. Shuttle Imaging Radar-C (SIR-C) data of 1994 and Advanced Land Observation Satellite (ALOS) PALSAR data of 2007 were used in this study. ALOS PALSAR data were orthorectified with Shuttle Radar Topographic Mission digital elevation model data. Image to image geometric registration was done between the two SAR scenes. Study area was clipped and separated as subsets. SIR-C data (L- and C-bands) was in dual polarization (HH and HV) and PALSAR (L-band) was in quad-polarization (HH, HV, VH, and VV). Five different categories of land covers (forest, upland soil/shrubs, lowland soil, settlements, and water/wetlands) were recognized on both SAR scenes. An additional class representing forest re-growth could be identified only on SIR-C image. Both the images were classified using maximum likelihood algorithms. The classification accuracy was computed from the randomly selected independent validation pixels. The accuracy for forest is more than 83% except users accuracy computed for PALSAR image. Forest was reduced from 18,000 to 13,800 ha in the region during the study period. The results of this study will be useful for understanding the applicability of SAR to map and quantify forest cover changes in the tropics.

Limitation of 90 m SRTM DEM in drainage network delineation using D8 method—a case study in flat terrain of Bangladesh

Abstract: Bangladesh is the deltaic flood plain located in the lower ridge of the Ganges Brahmaputra and Meghna basins. The country is very flat having 40% of its landmass up to 10 m above the mean sea level. Shuttle Radar Topography Mission (SRTM) 90 m, i.e., 3-arc second digital elevation model (DEM) is being widely used to delineate river network and to extract catchment information using hydrology tool of ArcGIS. The hydrology tool uses the D8 method for extraction of drainage pattern. The study was carried out to find the limitation and suitability of 90 m SRTM DEM data in flat terrains especially in Bangladesh using ArcGIS. Twelve catchments of varying geomorphology were chosen from five hydrological zones of Bangladesh. Basin characteristics such as bifurcation ratio, drainage density, and channel slope of the catchments were estimated and analyzed to evaluate the suitability of 90 m SRTM DEM. The delineated catchments of slope 1:3,600 or more flat shows large deviation in river network alignment when compared with the digital river network developed by Bangladesh Water Development Board and with Google Earth’s images. The catchments having slope 1:2,850 and more steep were delineated correctly. The conclusion could not be established between slopes 1:2,850 and 1:3,600. The study also revealed that the catchment characteristics other than the slope have no effect on river network delineation.

Development of track log and point of interest management system using Free and Open Source Software

Abstract: Recent advanced performance of low-cost Global Positioning System (GPS) and GPS-enabled cell phones has contributed a great deal to the development of location-aware services and systems. High-speed broadband technology has promoted collaborative projects such as OpenStreetMap or other User Generated Contents services. In this research, a Web-based prototype system for GPS track log and point of interest (POI) management was developed to archive a collaborative framework in field surveys. The main function of the system can be separated into three parts: data collection, data management, and data quality enhancement. The system supports real-time data collection for the future ubiquitous environment and also can monitor real-time GPS positions. This research shows functionalities that can minimize GPS errors using Dilution of Precision filtering and data quality enhancing techniques using the Douglas-Peucker algorithm and PgRouting. The research introduces a system that provides an interoperable framework in which to work with other geospatial services through open geospatial standards.

Use of spectral analysis for detection of alterations in ETM data, Yazd, Iran

Abstract: Spectral analysis methods were used for detection of mineralogical features on a set of Enhanced Thematic Mapper Plus data of Behabad zone, central Iran. Several indicative minerals for hydrothermal alterations were identified in the study area. The spectra of unknowns were determined by comparing to USGS mineral spectral library. Different pre-processings and processings were performed to achieve the highest possible accuracy. These are the minimum noise fraction, the pixel purity index analysis, spectral feature fitting, spectral angle mapper and binary encoding. The results of spectral analysis, as a map of minerals abundances, along with the results of other Image processing methods such as least square fit, and Crosta method were integrated within ArcGIS Software to achive a potential map of hydrothermal alterations. The minerals: allanite, magnetite, alunite, clay minerals, and muscovite were therefore detected and mapped in this study. The detected alterations here highly match to the mineral concentrations which are formerly found and measured in the study area that emphasizes the reliability of the applied method.

Investigation of fusion of SAR and Landsat data for shoreline super resolution mapping: the northeastern Mediterranean Sea coast in Egypt

Abstract: A shoreline is defined as the line of contact between land and water surface. Shoreline extraction/mapping is critical in many coastal zone applications such as safe navigation and coastal environmental protection. Digitizing a feature such as the coastline is a very tedious and time-consuming operation. In this research shoreline mapping at a sub-pixel and pixel levels was evaluated in the northern part of the coastal zone of Egypt (Port Said). Three different image fusion techniques have been used to merge two co-registered data, radar (Radarsat) and optical (Landsat), to improve the classification accuracy. Spatial, spectral, and radiometric qualities of the fused images have been evaluated. The resulted three fused images, the Landsat and Radarsat images, were fed to the fuzzy and the maximum likelihood classifiers where the classification delineated two classes; water and nonwater. The accuracy of the classified images was estimated based on a reference data. After classification, the results have been compared where it was found that image fusion has improved the classification accuracy and the accuracy of the fuzzy classification is better than the maximum likelihood classification in all cases. The best resulted classified image from the ten cases is that obtained from the fused Radarsat-Landsat images using IHS technique that was classified with the fuzzy classifier. Shoreline has been extracted from the (IHS-fuzzy), (SAR-fuzzy), and (Landsat-fuzzy). Experimental results showed that the shoreline extraction accuracy is dramatically improved by the effective image fusion of Landsat and SAR data. The accuracies of the extracted shorelines from (Landsat-fuzzy), (Radarsat-fuzzy), and (IHS-fuzzy) data based on twenty differential GPS check points are estimated to be 5.69, 5.26, and 5.14 m, respectively. The three shorelines extracted/mapped from (Landsat-fuzzy), (Radarsat-fuzzy), (IHS-fuzzy) data were compared to a reference shoreline. The RMS has been computed related to thirty checkpoints on the reference shoreline. The accuracies of the extracted shorelines from (Landsat-fuzzy), (SAR-fuzzy), and (IHS-fuzzy) data are estimated to be 8.3, 7.27, and 6.75 m, respectively. The positional quality of the extracted shorelines (using generalization factor) from (Landsat-fuzzy), (SAR-fuzzy), and (IHS-fuzzy) data are estimated to be 0.977, 0.986, and 0.999, respectively.

LiDAR digital building models for true orthophoto generation

Abstract: The importance of digital orthophotos in spatial databases has increased in recent years, since they are an efficient, low-cost and, if properly managed, accurate product. Usually, the generation of orthophotos is carried out using digital terrain models (DTMs); meaning without taking into account vegetation, buildings, and other attached and detached structures. This leads to low accuracies in urban areas, bringing distortions into the image. To avoid this unwanted effect, one must adopt a digital surface model (DSM), as proposed by Amhar et al. (Int Arch Photogrammetry Remote Sens 32(4):16-22, 1998). The method proposed in this paper allows for the creation of true orthophotos by using a DSM to refine the representation of buildings. The pixel size of the DSM must be similar to that of the true orthophoto in order to model the roof edges with sufficient accuracy. This paper presents a new method capable of correcting the roof displacement using an approach based on the integration of several products today available in public administrations, such as a geodatabase, DTMs/DSMs, and light detection and ranging (LiDAR) data. The method is based on a rigorous modelling of simple roofs starting from their 2D projection in the geodatabase, while information about their heights can be obtained using LiDAR data. For some selected simple roofs, automatic modelling can be carried out, in which a robust interpolation method, such as RANSAC, is used to model the pitches identified by a clustering procedure. For complex roofs, where creating a rigorous model in a fully automatic way is not possible, a procedure based on the thickening of a DSM is carried out.

Indicator kriging modeling epidemiology of common bean anthracnose

Abstract: The present work aims to characterize the spatial variability of common bean (Phaseolus vulgaris L.) anthracnose (Colletotrichum lindemuthianum (Sacc. & Magnus) Briosi & Cavara) using indicator kriging systems and nonlinear regression models. Seeds inoculated with a hydric restriction technique at −1 MPa were sowed in the center of plots as a pointwise inoculum source during a rainy and a drought season. The disease incidence was evaluated 26, 33, 40, 47, 54, and 61 days after sowing, in both considered seasons. Spacewise patterns of the disease were influenced by weather conditions and sprinkler irrigation. Based on spherical semivariogram models and kriging probability maps, the disease was disseminated around the primary inoculum source presenting strongly aggregated pattern in the rainy season. Disease presents higher aggressiveness in the drought period, spreading with secondary inoculum sources that became coalescent over time. Power model describes the increase of disease range variation over time in the rainy and drought seasons, with higher range values in the drought period.

Utilizing 3-D topographical information for the quality assessment of a satellite surveying

Abstract: Fostered by the rapid development of spatial information techniques, three-dimensional topographical information (e.g., digital terrain models and digital surface models) of a higher quality is becoming accessible to the public. The main emphasis of this study is on developing a satellite visibility and quality assessment technique for a global navigation and satellite system utilizing high-resolution 3-D topographical information. An adaptive sampling and analysis procedure is proposed to increase the computational efficiency while processing high-resolution topographical data. Additionally, a unified least-squares approach is introduced to realistically model the uncertainties in satellite orbits. Finally, simulation tests and global positioning system (GPS) field work have been performed to demonstrate the performance and capability of the proposed approach. The results reveal a significant improvement in efficiency and reliability for the quality estimation of a satellite surveying. Consequently, the proposed approach will benefit applications in which a pre-evaluation of the positioning quality is of a major concern for a satellite surveying (e.g., GPS field planning or network design).

The contribution of the digital elevation models and geographic information systems in a watershed hydrologic research

Abstract: The hydrological and physical characteristic description of a watershed constitutes an essential task for hydrologic research. Usually, this one requires a hydrologic model of which the running needs a great number of data and information. The main purpose of this study was to use Shuttle Radar Topography Mission (SRTM) data, free of charge, for hydrologic studies in Algeria. This work will also be a good assessment test of hydrologic geospatial tools HEC-GeoHMS integrated in the ESRI ArcView 3.2 GIS. It is to define the watershed of Macta and its sub-basins and to extract the hydrographical network and also other topographic and hydrologic parameters from the SRTM data. The data bank with the obtained results and the schematisation of the studied watershed (Macta watershed is in the western of Algeria) will be used as a foundation of a hydrologic model.

A case study comparing landscape metrics to geologic and seismic data from the Ischia Island (Southern Italy)

Abstract: In this paper, a high-resolution digital elevation model (DEM) of the Ischia Island has been created, and a digital terrain analysis has been carried out to identify of morphostructural elements of this landscape. Ischia is an active volcano located in the Western sector of the Gulf of Naples that is characterized by historical and recent volcano-tectonic activity. The local kinematics is unclear, and so identification of tectonic lineaments might elucidate recent tectonic processes. We identify morphostructural features using geomorphic parameters derived from analysis of the high-resolution DEM. Successively, the comparison with known geologic features provides validation of the extracted morphotectonic data. We found that one of the main directions of the morphostructural lineaments extracted is consistent with the regional NE-SW extensional stress field; moreover, the lineaments on the northern flank of Mt. Epomeo are strictly correlated with the mapped faults that have a history of strong and moderate earthquakes. The technique implemented for this study area allowed us to identify new original morphostructural lineaments in a reproducible way that may be useful for investigating various landscapes where field survey is not possible. Indeed, the extracted lineaments represent potential active faults near the northern coast of the Ischia Island, where both seismicity and intense urbanization delineate a high seismic risk.

Fire-prone areas delineated from a combination of the Nesterov Fire-risk Rating Index with multispectral satellite data

Abstract: Traditional fire-risk rating indices are founded on statistical relations between pre-event meteorological conditions and the number of fire outbreaks observed in a forested area. However, traditional weather-based indices cannot render information on the spatial distribution of fire-susceptible sites over extensive forested areas because their only inputs are meteorological observations made at sparsely distributed weather stations. Therefore, only an area-averaged value of the risk of fire can be obtained from these indices. This disadvantage can be relieved by using remote sensing data from polar-orbiting satellites scanning the Earth's surface in the visible and thermal spectral regions. This paper presents a synthesis of the Nesterov Fire-rating Index, an index extensively used in Central and Eastern Europe—and how this was merged with the Temperature–Vegetation Dryness Index (TVDI) derived from multispectral images scanned by Landsat ETM+. This paper demonstrates the methodology of how TVDI was merged with the Nesterov Index to give a map of the spatial patterns of fire-prone sites. The test region is located in a pine-forested (dominated by Pinus sylvestris) area in western Slovakia. Our investigation suggests that coupling TVDI with the Nesterov Index, or any other weather-based fire-rating index, can become an effective tool for delineating areas prone to fire outbreaks even in regions with insufficient coverage of weather stations.

The employment of terrestrial laser scanner in cultural heritage conservation: the case study of Vallinotto Chapel in Carignano-Italy

Abstract: Terrestrial laser scanner is a key methodology in cultural heritage survey, as it allows representing objects with high accuracy from the geometric point of view but allows also generating graphic representation of high visual impact for public (nontechnical) audience. The case study is a Vittone’s chapel, located in Carignano (Turin Province, NW Italy) characterized by a complex internal structure due to multiple layers of arches and other structures. The role of these features is not only structural but also figurative in order to represent, in the Chapel, the different levels of celestial hierarchy. The Chapel is now involved in a documentation project and thanks to the presence of scaffolding structures different scans have been carried out with an Optech-ILRIS 3D instrument. In the same time, using a calibrated digital camera, different pictures of the building have been taken. Scans have been accomplished at three different levels, due to scaffolding height, (10 m, 6 m, and ground) in order to obtain a complete survey of the building interior. A second series of scans has then been made in order to measure the exterior of the building. In the same time a classical topographical survey has been performed, using a no prism Sokkia total station, with the purpose of measuring tie point therefore used to merge the internal and external scans and to assess the alignment phase’s accuracy. The final model has then been processed in order to project calibrated images on some test areas through orthoimage generation.

Doppler measurement integration for kinematic real-time GPS positioning

Abstract: The present paper discusses the advantages of the use of Doppler shift measurements in a Kalman filter estimator in order to improve the kinematic stand-alone global positioning system positioning performance. Tests conducted in an urban environment using a single-frequency receiver demonstrate the real advantages of the proposed real-time computation technique.

Wireless sensor networks and their applications in geomatics: case study on developments in developing countries

Abstract: We are at a time of transition in the fields of planetary geodesy, mapping, and imaging. Planetary exploration has moved from a time of initial reconnaissance of the solar system using mostly planetary flyby missions and images exclusively from framing cameras to much more extensive missions of targeted exploration using orbiting spacecraft, line-scanner cameras, laser altimeters, and other sensors. It is appropriate to review the past history of this effort, recent advances in this area, and the current state of the art in both planetary and terrestrial geodesy, mapping, planetary imaging and surveillance, and reference systems. A wireless sensor network is a network consisting of small sensing devices spatially distributed using sensors to cooperatively monitor various conditions (Romer and Mattern, IEEE Wireless Comm 11(6):54–61, 2004; Thomas Haenselmann, Sensornetworks, GFDL Wireless Sensor Network textbook, http://www.informatik.uni-mannheim.de/∼haensel/sn_book, 2006). So far, over 100 physical (light, pressure, humidity, etc.), chemical (gas, liquid, solid, etc.), and biological (DNA, protein, acoustics, etc.) properties can be sensed by using in situ sensing technology. With the presence of cheaper, miniature, faster, and smart in situ sensors, the increasing availability of abundant ubiquitous computing devices, wireless and mobile network access, and autonomous and intelligent geospatial software agents, distributed networked in situ sensing becomes clearly a technological trend. Sensor Webs can perform as an extensive monitoring and sensing system that provides timely, comprehensive, continuous, and multi-mode observations on underground mining, wildlife, and various physical infrastructures such as bridges, pipelines, and buildings. These new earth-observation systems open up new avenues to fast assimilation of data from various sensors (both in situ and remote) and to accurate analysis and informed decision-makings. This paper studies the security aspects and present and future applications of these networks. The paper first introduces the revolutionary concept of the Sensor Web and provides a comprehensive study of Sensor Web (both Sensor Web and sensors mean the same), and then presents its related security problems, threats, risks, and characteristics. Additionally, the paper gives a brief introduction to the application and the opportunities available for these networks in rural India and thereby provides an opportunity to improve the quality of life which is integrated with that of domestic animal health, soil and water quality, and plant/crop health. We examine the possibility of setting up of sensor networks to monitor these aspects so as to provide a detailed set of information to the residents as well as planners.

Evaluation of the uncertainty of the length of energy distribution networks

Abstract: A statistical evaluation of the uncertainty of the length of a utility network is frequently omitted in current geographic information system (GIS) applications, although this information is important for management purposes. Nevertheless, the spatial database storing geographic information about the network might have been set up through a complex process (ground surveying, digitising of analogue maps, integration of different data sources), resulting in a dataset with unclassified uncertainty. This paper proposes a practical but ‘rigorous’ approach to evaluate the influence of the uncertainty in the determination of the length of a network. Starting from the definition of length uncertainty in terms of simple geometric elements (arc, pair of arcs, open and closed path), some rules for its evaluation in the case of complex networks have been developed. The statistical concept applied for the evaluation of uncertainty is quite standard because it is based on the covariance propagation theory. On the other hand, the influence of correlations between the lengths of adjacent elements has been considered as well. The application of this method only requires the topological structure of the network that can be built in a GIS environment. Furthermore, an alternative ‘approximate’ method is proposed to find an approximation of the uncertainty of the network length with a simple formula, which requires neither any particular processing step nor the network topology. Both methods have been tested and validated on simulated and real datasets.

Vertical gravity anomaly gradient effect of innermost zone on geoid-quasigeoid separation and an optimal integration radius in planar approximation

Abstract: This study mainly focuses on the solution of the vertical gravity anomaly gradient and determination of its effect on the total geoid-quasigeoid separation. Due to its small effect on geoid-quasigeoid separation, the planar approximation of vertical gravity anomaly in the innermost zone has been implemented. The computation of a strongly singular integral expressing the vertical gravity anomaly gradient was used for this purpose for even order (up to n = 6) of the Simpson and Newton–Cotes integration technique. The derivation of the relationships for different integration radii has been made to obtain these solutions using gridded data of free air anomaly. The comparison of relationships for the different integration radii was made in order to select an optimum radius of the integration in planar approximation for the vertical gravity anomaly gradient dependent geoid-quasigeoid separation term. The integration radii of 3.1, 6.2 and 9.3 km show an increasing behaviour towards saturation. The effect of vertical gravity anomaly gradient has similar pattern on the geoid-quasigeoid separation term towards saturation. The saturation trend for vertical gravity anomaly gradient is comparatively faster than its corresponding geoid-quasigeoid separation dependent term. The results also show that 2nd order Newton–Cotes integration is found to be comparable with the approximate linear solution for the vertical gravity anomaly gradient given by Heiskanen and Moritz. The vertical gravity anomaly dependant term has a rather small effect on geoid-quasigeoid separation in the mid elevation range and ranges from −6.18 to 2.7 mm for n = 6. The findings of the study leads to the inferences that the order of integration should be selected either n = 4 or n = 6 for better estimates of vertical gravity anomaly gradient solution. This criterion is also valid for their effect on geoid-quasigeoid separation with planar approximation in the innermost zone for the low- to mid-range elevation areas.