The spatial calculation of vector data is crucial for geochemical analysis in geological big data... more The spatial calculation of vector data is crucial for geochemical analysis in geological big data. However, large volumes of geochemical data make for inefficient management. Therefore, this study proposed a shapefile storage method based on MongoDB in GeoJSON form (SSMG) and a shapefile storage method based on PostgreSQL with open location code (OLC) geocoding (SSPOG) to solve the problem of low efficiency of electronic form management. The SSMG method consists of a JSONification tier and a cloud storage tier, while the SSPOG method consists of a geocoding tier, an extension tier, and a storage tier. Using MongoDB and PostgreSQL as databases, this study achieved two different types of high-throughput and high-efficiency methods for geochemical data storage and retrieval. Xinjiang, the largest province in China, was selected as the study area in which to test the proposed methods. Using geochemical data from shapefile as a data source, several experiments were performed to improve g...
Water resources are increasingly under stress in Central Asia because downstream countries are hi... more Water resources are increasingly under stress in Central Asia because downstream countries are highly dependent on upstream countries. Water is essential for irrigation and is becoming scarcer due to climate change and human activities. Based on 20 hydrological stations, this study firstly analyzed the annual and seasonal spatial–temporal changes of the river discharges, precipitation, and temperature in the Syr Darya River Basin and then the possible relationships between these factors were detected. Finally, the potential reasons for the river discharge variations have been discussed. The results show that the river discharges in the upper stream of the basin had significantly risen from 1930 to 2006, mainly due to the increase in temperature (approximately 0.3 °C per decade), which accelerated the melting of glaciers, while it decreased in the middle and lower regions due to the rising irrigation. In the middle of the basin, the expansion of the construction land (128.83 km2/year...
In this short communication, we describe the shortcomings and pitfalls of a commonly used method ... more In this short communication, we describe the shortcomings and pitfalls of a commonly used method to detect ground materials that relies on setting thresholds for normalized difference indices. We analyze this method critically and present some experimental results on the USGS and ECOSTRESS spectral libraries and on real Sentinel-2 and Landsat-8 images. We demonstrate the risk of commission errors and provide some suggestions to reduce it.
Hydrological models are indispensable to describe and study hydrological conditions in catchments... more Hydrological models are indispensable to describe and study hydrological conditions in catchments. In case of fully distributed hydrological models there is a need for spatially distributed input data, which is often difficult and/or expensive to collect. Remote sensing potentially offers a relatively easy and cheap way of collecting spatially distributed information of the earth surface. Within the framework of the MAMUD project (Measuring and Modelling Urban Dynamics) one of the aims is to integrate remote sensing data into the hydrological modelling process. The fully distributed, grid based, rainfall-runoff model WetSpa is used and adapted for flexible input from remote sensing derived model parameters. The adapted model is applied on the River Tolka, an urban catchment, located in the greater Dublin area (Ireland). In strongly urbanised catchments the imperviousness of some land-cover types is of large influence on the amount and intensity of the surface runoff. Rather than using static land use maps, with subjectively defined average imperviousness for each class, direct measures of imperviousness are integrated into the WetSpa model. Proportions of imperviousness are estimated by means of a sub-pixel classification technique: using a high-resolution Quickbird image a timeseries of 4 sub-pixel imperviousness maps is derived from Landsat imagery (1988, 1994, 1997 and 2001). This time-series is integrated into the rainfall-runoff modelling for the period 1985-2005. The modelling results are compared to the original results, i.e. simulation using static land use classes. The simulation with sub-pixel imperviousness yields a considerable difference in peak discharges, confirming its status as key factor in describing the hydrological dynamics in urban catchments. Next to the integration of sub-pixel imperviousness maps it is shown that further integration of remote sensing information, such as vegetation index based parameterization and evapotranspiration estimates, will result in a more accurate estimation of the runoff. Acknowledgements: This research is funded by the Belgian Science Policy Office within the framework of the STEREO II programma - project SR/00/105.
Hydrological models are indispensable to describe and study hydrological conditions in catchments... more Hydrological models are indispensable to describe and study hydrological conditions in catchments. In case of fully distributed hydrological models there is a need for spatially distributed input data, which is often difficult and/or expensive to collect. Remote sensing potentially offers a relatively easy and cheap way of collecting spatially distributed information of the earth surface. Within the framework of the MAMUD project (Measuring and Modelling Urban Dynamics) one of the aims is to integrate remote sensing data into the hydrological modelling process. The fully distributed, grid based, rainfall-runoff model WetSpa is used and adapted for flexible input from remote sensing derived model parameters. The adapted model is applied on the River Tolka, an urban catchment, located in the greater Dublin area (Ireland). In strongly urbanised catchments the imperviousness of some land-cover types is of large influence on the amount and intensity of the surface runoff. Rather than using static land use maps, with subjectively defined average imperviousness for each class, direct measures of imperviousness are integrated into the WetSpa model. Proportions of imperviousness are estimated by means of a sub-pixel classification technique: using a high-resolution Quickbird image a timeseries of 4 sub-pixel imperviousness maps is derived from Landsat imagery (1988, 1994, 1997 and 2001). This time-series is integrated into the rainfall-runoff modelling for the period 1985-2005. The modelling results are compared to the original results, i.e. simulation using static land use classes. The simulation with sub-pixel imperviousness yields a considerable difference in peak discharges, confirming its status as key factor in describing the hydrological dynamics in urban catchments. Next to the integration of sub-pixel imperviousness maps it is shown that further integration of remote sensing information, such as vegetation index based parameterization and evapotranspiration estimates, will result in a more accurate estimation of the runoff. Acknowledgements: This research is funded by the Belgian Science Policy Office within the framework of the STEREO II programma - project SR/00/105.
Abstract:[en] Prior to the commercial availability of Very High Resolution (VHR) satellite imager... more Abstract:[en] Prior to the commercial availability of Very High Resolution (VHR) satellite imagery, the applicability of Earth Observation data in the urban planning sector was very limited. The spatial resolution of the imagery, supplied by platforms like Landsat TM and ...
ABSTRACT Images from medium-resolution satellites are frequently used to study changes in urban v... more ABSTRACT Images from medium-resolution satellites are frequently used to study changes in urban vegetation or impervious surface cover over relatively long time periods. In this paper, we applied both ldquohardrdquo and ldquosoftrdquo mapping methods on two images covering the Brussels Capital Region in a time span of roughly 20 years. Although soft approaches are more accurate because they take the occurrence of mixed pixels into account, errors that result from the application of sub-pixel proportion estimation methods nevertheless propagate if the maps are used for change analysis. In this paper, we propose a method to take uncertainty in sub-pixel classification into account when producing change maps.
... Daniel McInerney Institute for Environment & Sustainability Joint Research Centre Europea... more ... Daniel McInerney Institute for Environment & Sustainability Joint Research Centre European Commission Ispra (VA), Italy Sheila Convery and Harutyun Shahumyan Urban Institute Ireland, University College Dublin Dublin, Ireland ...
The spatial calculation of vector data is crucial for geochemical analysis in geological big data... more The spatial calculation of vector data is crucial for geochemical analysis in geological big data. However, large volumes of geochemical data make for inefficient management. Therefore, this study proposed a shapefile storage method based on MongoDB in GeoJSON form (SSMG) and a shapefile storage method based on PostgreSQL with open location code (OLC) geocoding (SSPOG) to solve the problem of low efficiency of electronic form management. The SSMG method consists of a JSONification tier and a cloud storage tier, while the SSPOG method consists of a geocoding tier, an extension tier, and a storage tier. Using MongoDB and PostgreSQL as databases, this study achieved two different types of high-throughput and high-efficiency methods for geochemical data storage and retrieval. Xinjiang, the largest province in China, was selected as the study area in which to test the proposed methods. Using geochemical data from shapefile as a data source, several experiments were performed to improve g...
Water resources are increasingly under stress in Central Asia because downstream countries are hi... more Water resources are increasingly under stress in Central Asia because downstream countries are highly dependent on upstream countries. Water is essential for irrigation and is becoming scarcer due to climate change and human activities. Based on 20 hydrological stations, this study firstly analyzed the annual and seasonal spatial–temporal changes of the river discharges, precipitation, and temperature in the Syr Darya River Basin and then the possible relationships between these factors were detected. Finally, the potential reasons for the river discharge variations have been discussed. The results show that the river discharges in the upper stream of the basin had significantly risen from 1930 to 2006, mainly due to the increase in temperature (approximately 0.3 °C per decade), which accelerated the melting of glaciers, while it decreased in the middle and lower regions due to the rising irrigation. In the middle of the basin, the expansion of the construction land (128.83 km2/year...
In this short communication, we describe the shortcomings and pitfalls of a commonly used method ... more In this short communication, we describe the shortcomings and pitfalls of a commonly used method to detect ground materials that relies on setting thresholds for normalized difference indices. We analyze this method critically and present some experimental results on the USGS and ECOSTRESS spectral libraries and on real Sentinel-2 and Landsat-8 images. We demonstrate the risk of commission errors and provide some suggestions to reduce it.
Hydrological models are indispensable to describe and study hydrological conditions in catchments... more Hydrological models are indispensable to describe and study hydrological conditions in catchments. In case of fully distributed hydrological models there is a need for spatially distributed input data, which is often difficult and/or expensive to collect. Remote sensing potentially offers a relatively easy and cheap way of collecting spatially distributed information of the earth surface. Within the framework of the MAMUD project (Measuring and Modelling Urban Dynamics) one of the aims is to integrate remote sensing data into the hydrological modelling process. The fully distributed, grid based, rainfall-runoff model WetSpa is used and adapted for flexible input from remote sensing derived model parameters. The adapted model is applied on the River Tolka, an urban catchment, located in the greater Dublin area (Ireland). In strongly urbanised catchments the imperviousness of some land-cover types is of large influence on the amount and intensity of the surface runoff. Rather than using static land use maps, with subjectively defined average imperviousness for each class, direct measures of imperviousness are integrated into the WetSpa model. Proportions of imperviousness are estimated by means of a sub-pixel classification technique: using a high-resolution Quickbird image a timeseries of 4 sub-pixel imperviousness maps is derived from Landsat imagery (1988, 1994, 1997 and 2001). This time-series is integrated into the rainfall-runoff modelling for the period 1985-2005. The modelling results are compared to the original results, i.e. simulation using static land use classes. The simulation with sub-pixel imperviousness yields a considerable difference in peak discharges, confirming its status as key factor in describing the hydrological dynamics in urban catchments. Next to the integration of sub-pixel imperviousness maps it is shown that further integration of remote sensing information, such as vegetation index based parameterization and evapotranspiration estimates, will result in a more accurate estimation of the runoff. Acknowledgements: This research is funded by the Belgian Science Policy Office within the framework of the STEREO II programma - project SR/00/105.
Hydrological models are indispensable to describe and study hydrological conditions in catchments... more Hydrological models are indispensable to describe and study hydrological conditions in catchments. In case of fully distributed hydrological models there is a need for spatially distributed input data, which is often difficult and/or expensive to collect. Remote sensing potentially offers a relatively easy and cheap way of collecting spatially distributed information of the earth surface. Within the framework of the MAMUD project (Measuring and Modelling Urban Dynamics) one of the aims is to integrate remote sensing data into the hydrological modelling process. The fully distributed, grid based, rainfall-runoff model WetSpa is used and adapted for flexible input from remote sensing derived model parameters. The adapted model is applied on the River Tolka, an urban catchment, located in the greater Dublin area (Ireland). In strongly urbanised catchments the imperviousness of some land-cover types is of large influence on the amount and intensity of the surface runoff. Rather than using static land use maps, with subjectively defined average imperviousness for each class, direct measures of imperviousness are integrated into the WetSpa model. Proportions of imperviousness are estimated by means of a sub-pixel classification technique: using a high-resolution Quickbird image a timeseries of 4 sub-pixel imperviousness maps is derived from Landsat imagery (1988, 1994, 1997 and 2001). This time-series is integrated into the rainfall-runoff modelling for the period 1985-2005. The modelling results are compared to the original results, i.e. simulation using static land use classes. The simulation with sub-pixel imperviousness yields a considerable difference in peak discharges, confirming its status as key factor in describing the hydrological dynamics in urban catchments. Next to the integration of sub-pixel imperviousness maps it is shown that further integration of remote sensing information, such as vegetation index based parameterization and evapotranspiration estimates, will result in a more accurate estimation of the runoff. Acknowledgements: This research is funded by the Belgian Science Policy Office within the framework of the STEREO II programma - project SR/00/105.
Abstract:[en] Prior to the commercial availability of Very High Resolution (VHR) satellite imager... more Abstract:[en] Prior to the commercial availability of Very High Resolution (VHR) satellite imagery, the applicability of Earth Observation data in the urban planning sector was very limited. The spatial resolution of the imagery, supplied by platforms like Landsat TM and ...
ABSTRACT Images from medium-resolution satellites are frequently used to study changes in urban v... more ABSTRACT Images from medium-resolution satellites are frequently used to study changes in urban vegetation or impervious surface cover over relatively long time periods. In this paper, we applied both ldquohardrdquo and ldquosoftrdquo mapping methods on two images covering the Brussels Capital Region in a time span of roughly 20 years. Although soft approaches are more accurate because they take the occurrence of mixed pixels into account, errors that result from the application of sub-pixel proportion estimation methods nevertheless propagate if the maps are used for change analysis. In this paper, we propose a method to take uncertainty in sub-pixel classification into account when producing change maps.
... Daniel McInerney Institute for Environment & Sustainability Joint Research Centre Europea... more ... Daniel McInerney Institute for Environment & Sustainability Joint Research Centre European Commission Ispra (VA), Italy Sheila Convery and Harutyun Shahumyan Urban Institute Ireland, University College Dublin Dublin, Ireland ...
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Papers by Tim Van de Voorde