Klemen Zakšek | University of Hamburg (original) (raw)

Papers by Klemen Zakšek

Dans le cadre du projet ArchaeDyn un groupe de travail a été créé pour coordonner l'élaboration, ... more Dans le cadre du projet ArchaeDyn un groupe de travail a été créé pour coordonner l'élaboration, la mise en oeuvre et l'application de méthodes d'analyses spatiales et d'outils. Les activités de ce groupe ont été orientées par différents problèmes. Le premier concerne la création d'un réseau, commun à tous les groupes de travail et l'homogénéisation des zones d'études que les différents groupes de travail thématiques ont traité avec leurs bases de données. Une méthode, appelée cartes de confiance, a été proposée afin d'évaluer la qualité et la quantité des informations répertoriées dans les bases de données. Les cartes de confiance, produites par la combinaison simple des cartes de représentation et de fiabilité, peuvent être considérées comme un «masque» pour l'interprétation des résultats de l'analyse spatiale. L'équipe de recherche a également testé, développé et adapté différentes méthodes statistiques et géostatistiques pour définir des indicateurs spatiaux de stabilité dans le temps (durabilité / rythmes, mutations, mobilité / trajectoires).

Some applications e.g. from traffic management or energy meteorology require air temperature at 2... more Some applications e.g. from traffic management or energy meteorology require air temperature at 2 metres height above the ground in a high spatial and temporal resolution, partly even in near-real-time. Thus a parameterization based on boundary layer physical principles, which determines air temperature from remote sensing data (SEVIRI data aboard the MSG and MODIS data aboard Terra and Aqua satellites),

ISPRS Journal of Photogrammetry and Remote Sensing, 2009

Some applications, e.g. from traffic or energy management, require air temperature data in high s... more Some applications, e.g. from traffic or energy management, require air temperature data in high spatial and temporal resolution at two metres height above the ground (T2m), sometimes in near-real-time. Thus, a parameterization based on boundary layer physical principles was developed that determines the air temperature from remote sensing data (SEVIRI data aboard the MSG and MODIS data aboard Terra and Aqua

Some applications e.g. from traffic management or energy meteorology require air temperature at 2... more Some applications e.g. from traffic management or energy meteorology require air temperature at 2 metres height above the ground in a high spatial and temporal resolution, partly even in near-real-time. Thus a parameterization based on boundary layer physical principles, which determines air temperature from remote sensing data (SEVIRI data aboard the MSG and MODIS data aboard Terra and Aqua satellites), was developed. The method consists of two parts. First, a downscaling procedure from the SEVIRI pixel resolution of several kilometres to one kilometre spatial resolution is performed using a regression analysis between the land surface temperature (LST) and normalized differential vegetation index (NDVI) acquired by the MODIS instrument. Secondly, the data as albedo, downwelling surface short-and long-wave fluxes, relief characteristics and NDVI data are used as input parameters in the empirical parameterization that removes the lapse rate between LST and 2 m air temperature. The method was successfully tested for Slovenia, the French region Franche-Comté and southern Germany in May to December 2005 allowing the development of a parameterization valid for central Europe. This parameterisation results in a RMSD of 2.0 K during daytime with a bias of -0.01 K and a correlation coefficient of 0.95. This is a promising result especially considering the high temporal (30 min) and spatial resolution (1000 m) of the results.

RED SEED stands for Risk Evaluation, Detection and Simulation during Effusive Eruption Disasters,... more RED SEED stands for Risk Evaluation, Detection and Simulation during Effusive Eruption Disasters, and combines stakeholders from the remote sensing, modelling and response communities with experience in tracking volcanic effusive events. The group first met during a three day-long workshop held in Clermont Ferrand (France) between 28 and 30 May 2013. During each day, presentations were given reviewing the state of the art in terms of (a) volcano hot spot detection and parameterization, (b) operational satellite-based hot spot detection systems, (c) lava flow modelling and (d) response protocols during effusive crises. At the end of each presentation set, the four groups retreated to discuss and report on requirements for a truly integrated and operational response that satisfactorily combines remote sensors, modellers and responders during an effusive crisis. The results of collating the final reports, and follow-up discussions that have been on-going since the workshop, are given here. We can reduce our discussions to four main findings. (1) Hot spot detection tools are operational and capable of providing effusive eruption onset notice within 15 min. (2) Spectral radiance metrics can also be provided with high degrees of confidence. However, if we are to achieve a truly global system, more local receiving stations need to be installed with hot spot detection and data processing modules running on-site and in real time. (3) Models are operational, but need real-time input of reliable time-averaged discharge rate data and regular updates of digital elevation models if they are to be effective; the latter can be provided by the radar/photogrammetry community. (4) Information needs to be provided in an agreed and standard format following an ensemble approach and using models that have been validated and recognized as trustworthy by the responding authorities. All of this requires a sophisticated and centralized data collection, distribution and reporting hub that is based on a philosophy of joint ownership and mutual trust. While the next chapter carries out an exercise to explore the viability of the last point, the detailed recommendations behind these findings are detailed here.

This paper describes the contribution of path modelling to the ancient settlement pattern study o... more This paper describes the contribution of path modelling to the ancient settlement pattern study over the long term. The path modelling methodology is a stimulating tool, which is complementary to the hierarchical approaches in the landscape archaeology since it contributes to the understanding of the spatial relation between archaeological sites. The existing methodology was enhanced by enlarging the set of path reconstitution parameters (visibility) and by modelling in two scales. The proposed model is based on parameters derived merely from the relief because its changes should be insignificant even over a long period time.

The focus of interest in remote sensing for archaeology has shifted from aerial photography, whic... more The focus of interest in remote sensing for archaeology has shifted from aerial photography, which has been in use since the beginning of the previous century, towards multispectral and hyperspectral satellite imagery, and active techniques such as laser scanning. With airborne laser scanning we can observe details with high elevation accuracy and with a spatial resolution of less than one meter. However, an effective interpretation of the digital elevation models (DEMs) created from these data requires appropriate visualization. Hill-shading is the most frequently used relief visualization technique and is well suited for printed maps. Several authors have tried to overcome its limitations by using multiple angle shading and filtering. The sky-view factor is a new method that computes the portion of visible sky limited by the relief for every point on the ground. By applying it to lidar data we have been able to accurately map unknown archaeological sites and update the existing maps. Sky-view factor additionally proved to be a superior visualization technique as it reveals small relief features while preserving the perception of general topography. Rather than just presenting or visualizing the same information in a new way it extracts new information that can be further processed. In addition to the studies of the past cultural and natural landscapes it can be effectively used in other scientific fields in which digital elevation model visualizations and automatic feature extraction techniques are indispensable, e.g. geography, geomorphology, cartography, hydrology, glaciology, forestry and disaster management.

Atmospheric and Climate Sciences, 2012

Spatial variations in temperature may be ascribed to many variables. Among these, variables perta... more Spatial variations in temperature may be ascribed to many variables. Among these, variables pertaining to topography are prominent. Thus various topographic variables were calculated from 50 m-resolution digital terrain models (DTMs) for three study areas in France and for Slovenia. The "classic" geomatic variables (altitude, aspect, gradient, etc.) are supplemented by the description of landforms (amplitude of humps and hollows). Special care is taken in managing collinearity among variables and building windows with different dimensions. Statistical processing involves linear regressions of daily temperatures taken as the response variables and six topographic variables (explanatory variables). Altitude accounts significantly for the spatial variation in temperatures in 90% of cases, except in the Gironde, a lowlying area (50%). The scale of landforms also appears to be highly correlated to the measured temperature. Variations in the frequency with which topographic descriptors account for temperatures are examined from several standpoints. Altitude is less frequently taken as an explanatory variable for spatial variation of temperatures in winter (75%) than in spring (80%) and late summer (85%). Minimum temperatures are influenced on average much more by the amplitude of humps and hollows (56%) than maximum temperatures (38%) are. The frequency with which these two landforms account for the spatial variation of temperature is reversed between the minima and maxima.

IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 2014

Geodetski vestnik, 2010

Daljinsko zaznavanje v termičnem infrardečem spektru je sodobno orodje, ki nam omogoča opazovanje... more Daljinsko zaznavanje v termičnem infrardečem spektru je sodobno orodje, ki nam omogoča opazovanje aktivnih ognjenikov. Z njim lahko zaznamo manjše toplotne anomalije, kot so vroči izviri ali fumarole, pa tudi večja telesa, kot so tokovi ali jezera lave. Vse anomalije imajo ne glede na temperaturo običajno manjšo površino od prostorske ločljivosti senzorjev (od 30 do 4000 m), ki so primerni za njihovo opazovanje. Da bi lahko anomalijo kljub temu zaznali in določili njene fizikalne parametre, moramo uporabiti podatke iz več kanalov v ustreznem spektru. Toplotno anomalijo najbolj robustno opišemo s toplotnim tokom. Za razumevanje aktivnosti ognjenika moramo spremljati razvoj časovne vrste toplotnega toka. Ker so satelitski podatki podvrženi vplivom atmosfere, reliefa, itd., je v časovni vrsti vedno prisoten šum. Kot primer smo prikazali zmanjšanje šuma s kalmanovim filtrom, s katerim smo obdelali izbruh Etne jeseni 2002. KLJUČNE BESEDE termično daljinsko zaznavanje, ognjenik, toplotni tok, kalmanov filter thermal remote sensing, volcano, radiative heat flux, Kalman filter UDK: 528.7:528.9

Theory, Practice and Interpretation of Factors and Effects of Long Term Landscape Formation and Transformation, 2014

Some applications e.g. from traffic management or energy meteorology require air temperature at 2... more Some applications e.g. from traffic management or energy meteorology require air temperature at 2 metres height above the ground in a high spatial and temporal resolution, partly even in near-real-time. Thus a parameterization based on boundary layer physical principles, which determines air temperature from remote sensing data (SEVIRI data aboard the MSG and MODIS data aboard Terra and Aqua satellites), was developed. The method consists of two parts. First, a downscaling procedure from the SEVIRI pixel resolution of several kilometres to one kilometre spatial resolution is performed using a regression analysis between the land surface temperature (LST) and normalized differential vegetation index (NDVI) acquired by the MODIS instrument. Secondly, the data as albedo, downwelling surface short-and long-wave fluxes, relief characteristics and NDVI data are used as input parameters in the empirical parameterization that removes the lapse rate between LST and 2 m air temperature. The method was successfully tested for Slovenia, the French region Franche-Comté and southern Germany in May to December 2005 allowing the development of a parameterization valid for central Europe. This parameterisation results in a RMSD of 2.0 K during daytime with a bias of -0.01 K and a correlation coefficient of 0.95. This is a promising result especially considering the high temporal (30 min) and spatial resolution (1000 m) of the results.

Dans le cadre du projet ArchaeDyn un groupe de travail a été créé pour coordonner l'élaboration, ... more Dans le cadre du projet ArchaeDyn un groupe de travail a été créé pour coordonner l'élaboration, la mise en oeuvre et l'application de méthodes d'analyses spatiales et d'outils. Les activités de ce groupe ont été orientées par différents problèmes. Le premier concerne la création d'un réseau, commun à tous les groupes de travail et l'homogénéisation des zones d'études que les différents groupes de travail thématiques ont traité avec leurs bases de données. Une méthode, appelée cartes de confiance, a été proposée afin d'évaluer la qualité et la quantité des informations répertoriées dans les bases de données. Les cartes de confiance, produites par la combinaison simple des cartes de représentation et de fiabilité, peuvent être considérées comme un «masque» pour l'interprétation des résultats de l'analyse spatiale. L'équipe de recherche a également testé, développé et adapté différentes méthodes statistiques et géostatistiques pour définir des indicateurs spatiaux de stabilité dans le temps (durabilité / rythmes, mutations, mobilité / trajectoires).

Some applications e.g. from traffic management or energy meteorology require air temperature at 2... more Some applications e.g. from traffic management or energy meteorology require air temperature at 2 metres height above the ground in a high spatial and temporal resolution, partly even in near-real-time. Thus a parameterization based on boundary layer physical principles, which determines air temperature from remote sensing data (SEVIRI data aboard the MSG and MODIS data aboard Terra and Aqua satellites),

ISPRS Journal of Photogrammetry and Remote Sensing, 2009

Some applications, e.g. from traffic or energy management, require air temperature data in high s... more Some applications, e.g. from traffic or energy management, require air temperature data in high spatial and temporal resolution at two metres height above the ground (T2m), sometimes in near-real-time. Thus, a parameterization based on boundary layer physical principles was developed that determines the air temperature from remote sensing data (SEVIRI data aboard the MSG and MODIS data aboard Terra and Aqua

Some applications e.g. from traffic management or energy meteorology require air temperature at 2... more Some applications e.g. from traffic management or energy meteorology require air temperature at 2 metres height above the ground in a high spatial and temporal resolution, partly even in near-real-time. Thus a parameterization based on boundary layer physical principles, which determines air temperature from remote sensing data (SEVIRI data aboard the MSG and MODIS data aboard Terra and Aqua satellites), was developed. The method consists of two parts. First, a downscaling procedure from the SEVIRI pixel resolution of several kilometres to one kilometre spatial resolution is performed using a regression analysis between the land surface temperature (LST) and normalized differential vegetation index (NDVI) acquired by the MODIS instrument. Secondly, the data as albedo, downwelling surface short-and long-wave fluxes, relief characteristics and NDVI data are used as input parameters in the empirical parameterization that removes the lapse rate between LST and 2 m air temperature. The method was successfully tested for Slovenia, the French region Franche-Comté and southern Germany in May to December 2005 allowing the development of a parameterization valid for central Europe. This parameterisation results in a RMSD of 2.0 K during daytime with a bias of -0.01 K and a correlation coefficient of 0.95. This is a promising result especially considering the high temporal (30 min) and spatial resolution (1000 m) of the results.

RED SEED stands for Risk Evaluation, Detection and Simulation during Effusive Eruption Disasters,... more RED SEED stands for Risk Evaluation, Detection and Simulation during Effusive Eruption Disasters, and combines stakeholders from the remote sensing, modelling and response communities with experience in tracking volcanic effusive events. The group first met during a three day-long workshop held in Clermont Ferrand (France) between 28 and 30 May 2013. During each day, presentations were given reviewing the state of the art in terms of (a) volcano hot spot detection and parameterization, (b) operational satellite-based hot spot detection systems, (c) lava flow modelling and (d) response protocols during effusive crises. At the end of each presentation set, the four groups retreated to discuss and report on requirements for a truly integrated and operational response that satisfactorily combines remote sensors, modellers and responders during an effusive crisis. The results of collating the final reports, and follow-up discussions that have been on-going since the workshop, are given here. We can reduce our discussions to four main findings. (1) Hot spot detection tools are operational and capable of providing effusive eruption onset notice within 15 min. (2) Spectral radiance metrics can also be provided with high degrees of confidence. However, if we are to achieve a truly global system, more local receiving stations need to be installed with hot spot detection and data processing modules running on-site and in real time. (3) Models are operational, but need real-time input of reliable time-averaged discharge rate data and regular updates of digital elevation models if they are to be effective; the latter can be provided by the radar/photogrammetry community. (4) Information needs to be provided in an agreed and standard format following an ensemble approach and using models that have been validated and recognized as trustworthy by the responding authorities. All of this requires a sophisticated and centralized data collection, distribution and reporting hub that is based on a philosophy of joint ownership and mutual trust. While the next chapter carries out an exercise to explore the viability of the last point, the detailed recommendations behind these findings are detailed here.

This paper describes the contribution of path modelling to the ancient settlement pattern study o... more This paper describes the contribution of path modelling to the ancient settlement pattern study over the long term. The path modelling methodology is a stimulating tool, which is complementary to the hierarchical approaches in the landscape archaeology since it contributes to the understanding of the spatial relation between archaeological sites. The existing methodology was enhanced by enlarging the set of path reconstitution parameters (visibility) and by modelling in two scales. The proposed model is based on parameters derived merely from the relief because its changes should be insignificant even over a long period time.

The focus of interest in remote sensing for archaeology has shifted from aerial photography, whic... more The focus of interest in remote sensing for archaeology has shifted from aerial photography, which has been in use since the beginning of the previous century, towards multispectral and hyperspectral satellite imagery, and active techniques such as laser scanning. With airborne laser scanning we can observe details with high elevation accuracy and with a spatial resolution of less than one meter. However, an effective interpretation of the digital elevation models (DEMs) created from these data requires appropriate visualization. Hill-shading is the most frequently used relief visualization technique and is well suited for printed maps. Several authors have tried to overcome its limitations by using multiple angle shading and filtering. The sky-view factor is a new method that computes the portion of visible sky limited by the relief for every point on the ground. By applying it to lidar data we have been able to accurately map unknown archaeological sites and update the existing maps. Sky-view factor additionally proved to be a superior visualization technique as it reveals small relief features while preserving the perception of general topography. Rather than just presenting or visualizing the same information in a new way it extracts new information that can be further processed. In addition to the studies of the past cultural and natural landscapes it can be effectively used in other scientific fields in which digital elevation model visualizations and automatic feature extraction techniques are indispensable, e.g. geography, geomorphology, cartography, hydrology, glaciology, forestry and disaster management.

Atmospheric and Climate Sciences, 2012

Spatial variations in temperature may be ascribed to many variables. Among these, variables perta... more Spatial variations in temperature may be ascribed to many variables. Among these, variables pertaining to topography are prominent. Thus various topographic variables were calculated from 50 m-resolution digital terrain models (DTMs) for three study areas in France and for Slovenia. The "classic" geomatic variables (altitude, aspect, gradient, etc.) are supplemented by the description of landforms (amplitude of humps and hollows). Special care is taken in managing collinearity among variables and building windows with different dimensions. Statistical processing involves linear regressions of daily temperatures taken as the response variables and six topographic variables (explanatory variables). Altitude accounts significantly for the spatial variation in temperatures in 90% of cases, except in the Gironde, a lowlying area (50%). The scale of landforms also appears to be highly correlated to the measured temperature. Variations in the frequency with which topographic descriptors account for temperatures are examined from several standpoints. Altitude is less frequently taken as an explanatory variable for spatial variation of temperatures in winter (75%) than in spring (80%) and late summer (85%). Minimum temperatures are influenced on average much more by the amplitude of humps and hollows (56%) than maximum temperatures (38%) are. The frequency with which these two landforms account for the spatial variation of temperature is reversed between the minima and maxima.

IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 2014

Geodetski vestnik, 2010

Daljinsko zaznavanje v termičnem infrardečem spektru je sodobno orodje, ki nam omogoča opazovanje... more Daljinsko zaznavanje v termičnem infrardečem spektru je sodobno orodje, ki nam omogoča opazovanje aktivnih ognjenikov. Z njim lahko zaznamo manjše toplotne anomalije, kot so vroči izviri ali fumarole, pa tudi večja telesa, kot so tokovi ali jezera lave. Vse anomalije imajo ne glede na temperaturo običajno manjšo površino od prostorske ločljivosti senzorjev (od 30 do 4000 m), ki so primerni za njihovo opazovanje. Da bi lahko anomalijo kljub temu zaznali in določili njene fizikalne parametre, moramo uporabiti podatke iz več kanalov v ustreznem spektru. Toplotno anomalijo najbolj robustno opišemo s toplotnim tokom. Za razumevanje aktivnosti ognjenika moramo spremljati razvoj časovne vrste toplotnega toka. Ker so satelitski podatki podvrženi vplivom atmosfere, reliefa, itd., je v časovni vrsti vedno prisoten šum. Kot primer smo prikazali zmanjšanje šuma s kalmanovim filtrom, s katerim smo obdelali izbruh Etne jeseni 2002. KLJUČNE BESEDE termično daljinsko zaznavanje, ognjenik, toplotni tok, kalmanov filter thermal remote sensing, volcano, radiative heat flux, Kalman filter UDK: 528.7:528.9

Theory, Practice and Interpretation of Factors and Effects of Long Term Landscape Formation and Transformation, 2014

Some applications e.g. from traffic management or energy meteorology require air temperature at 2... more Some applications e.g. from traffic management or energy meteorology require air temperature at 2 metres height above the ground in a high spatial and temporal resolution, partly even in near-real-time. Thus a parameterization based on boundary layer physical principles, which determines air temperature from remote sensing data (SEVIRI data aboard the MSG and MODIS data aboard Terra and Aqua satellites), was developed. The method consists of two parts. First, a downscaling procedure from the SEVIRI pixel resolution of several kilometres to one kilometre spatial resolution is performed using a regression analysis between the land surface temperature (LST) and normalized differential vegetation index (NDVI) acquired by the MODIS instrument. Secondly, the data as albedo, downwelling surface short-and long-wave fluxes, relief characteristics and NDVI data are used as input parameters in the empirical parameterization that removes the lapse rate between LST and 2 m air temperature. The method was successfully tested for Slovenia, the French region Franche-Comté and southern Germany in May to December 2005 allowing the development of a parameterization valid for central Europe. This parameterisation results in a RMSD of 2.0 K during daytime with a bias of -0.01 K and a correlation coefficient of 0.95. This is a promising result especially considering the high temporal (30 min) and spatial resolution (1000 m) of the results.