Palmer, S.C.J., Pelevin, V.V., Goncharenko, I., Kovács, A.W., Zlinszky, A., Présing, M., Horvát... more Palmer, S.C.J., Pelevin, V.V., Goncharenko, I., Kovács, A.W., Zlinszky, A., Présing, M., Horváth, H., Nicolás-Perea, V., Balzter, H. and Tóth, V.R. (2013): Ultraviolet Fluorescence LiDAR (UFL) as a robust measurement tool for water quality parameters in turbid lake conditions, Remote Sensing 5, 4405-4422; doi:10.3390/rs5094405, http://hdl.handle.net/2381/28884
The hydrology of Lake Balaton, the largest lake in Central Europe has a long history of human imp... more The hydrology of Lake Balaton, the largest lake in Central Europe has a long history of human impact, which probably started in prehistoric times through agricultural expansion. The most important change in the water regime of the Lake is considered to be the opening of the Sió Canal in 1863. This resulted in the lowering of the average water level
Outlining patches dominated by different plants in wetland vegetation provides
information on spe... more Outlining patches dominated by different plants in wetland vegetation provides information on species succession, microhabitat patterns, wetland health and ecosystem services. Aerial photogrammetry and hyperspectral imaging are the usual data acquisition methods but the application of airborne laser scanning (ALS) as a standalone tool also holds promises for this field since it can be used to quantify 3-dimensional vegetation structure. Lake Balaton is a large shallow lake in western Hungary with shore wetlands that have been in decline since the 1970s. In August 2010, an ALS survey of the shores of Lake Balaton was completed with 1 pt/m2 discrete echo recording. The resulting ALS dataset was processed to several output rasters describing vegetation and terrain properties, creating a sufficient number of independent variables for each raster cell to allow for basic multivariate classification. An expert-generated decision tree algorithm was applied to outline wetland areas, and within these, patches dominated by Typha sp. Carex sp., and Phragmites australis. Reed health was mapped into four categories: healthy, stressed, ruderal and die-back. The output map was tested against a set of 775 geo-tagged ground photographs and had a user’s accuracy of >97% for detecting non-wetland features (trees, artificial surfaces and low density Scirpus stands), >72% for dominant genus detection and >80% for most reed health categories (with 62% for one category). Overall classification accuracy was 82.5%, Cohen’s Kappa 0.80, which is similar to some hyperspectral or multispectral-ALS fusion studies. Compared to hyperspectral imaging, the processing chain of ALS can be automated in a similar way but relies directly on differences in vegetation structure and actively sensed reflectance and is thus probably more robust. The data acquisition parameters are similar to the national surveys of several European countries, suggesting that these existing datasets could be used for vegetation mapping and monitoring.
Socio-hydrology is the science of human influence
on hydrology and the influence of the water cyc... more Socio-hydrology is the science of human influence on hydrology and the influence of the water cycle on human social systems. This newly emerging discipline inherently involves a historic perspective, often focusing on timescales of several centuries. While data on human history is typically available for this time frame, gathering information on the hydrological situation during such a period can prove difficult: measured hydrological data for such long periods are rare, while models and secondary data sets from geomorphology, pedology or archaeology are typically not accurate enough over such a short time. In the first part of this study, the use of historic maps in hydrology is reviewed. Major breakthroughs were the acceptance of historic map content as valid data, the use of preserved features for investigating situations earlier than the map, and the onset of digital georeferencing and data integration. Historic maps can be primary quantitative sources of hydro-geomorphological information, they can provide a context for point-based measurements over larger areas, and they can deliver time series for a better understanding of change scenarios. In the second part, a case study is presented: water level fluctuations of Lake Balaton were reconstructed from maps, levelling logs and other documents. An 18th century map system of the whole 5700 km2 catchment was georeferenced, integrated with two 19th century map systems, and wetlands, forests and open water digitized. Changes in wetland area were compared with lake water level changes in a 220 yr time series. Historic maps show that the water level of the lake was closer to present-day levels than expected, and that wetland loss pre-dates drainage of the lake. The present and future role of historic maps is discussed. Historic hydrological data has to be treated with caution: while it is possible to learn form the past, the assumption that future changes will be like past changes does not always hold. Nevertheless, old maps are relatively accessible data sets and the knowledge base for using them is rapidly growing, and it can be expected that long-term time series will be established by integrating georeferenced map systems over large areas. In the Appendix, a step-by-step guide to using historic maps in hydrology is given, starting from finding a map, through georeferencing and processing the map to publication of the results.
There is increasing demand for reliable, high-resolution vegetation maps
covering large areas. Ai... more There is increasing demand for reliable, high-resolution vegetation maps covering large areas. Airborne laser scanning data is available for large areas with high resolution and supports automatic processing, therefore, it is well suited for habitat mapping. Lowland hay meadows are widespread habitat types in European grasslands, and also have one of the highest species richness. The objective of this study was to test the applicability of airborne laser scanning for vegetation mapping of different grasslands, including the Natura 2000 habitat type lowland hay meadows. Full waveform leaf-on and leaf-off point clouds were collected from a Natura 2000 site in Sopron, Hungary, covering several grasslands. The LIDAR data were processed to a set of rasters representing point attributes including reflectance, echo width, vegetation height, canopy openness, and surface roughness measures, and these were fused to a multi-band pseudo-image. Random forest machine learning was used for classifying this dataset. Habitat type, dominant plant species and other features of interest were noted in a set of 140 field plots. Two sets of categories were used: five classes focusing on meadow identification and the location of lowland hay meadows, and 10 classes, including eight different grassland vegetation categories. For five classes, an overall accuracy of 75% was reached, for 10 classes, this was 68%. The method delivers unprecedented fine resolution vegetation maps for management and ecological research. We conclude that high-resolution full-waveform LIDAR data can be used to detect grassland vegetation classes relevant for Natura 2000.
Natura 2000 Habitat Conservation Status is currently evaluated based on fieldwork.
However, this... more Natura 2000 Habitat Conservation Status is currently evaluated based on fieldwork.
However, this is proving to be unfeasible over large areas. The use of remote sensing is
increasingly encouraged but covering the full range of ecological variables by such datasets
and ensuring compatibility with the traditional assessment methodology has not been achieved
yet. We aimed to test Airborne Laser Scanning (ALS) as a source for mapping all variables
required by the local official conservation status assessment scheme and to develop
an automated method that calculates Natura 2000 conservation status at 0.5 m raster resolution
for 24 km2 of Pannonic Salt Steppe habitat (code 1530). We used multi-temporal (summer
and winter) ALS point clouds with full-waveform recording and a density of 10 pt/m2.
Some required variables were derived from ALS product rasters; others involved vegetation
classification layers calculated by machine learning and fuzzy categorization. Thresholds
separating favorable and unfavorable values of each variable required by the national
assessment scheme were manually calibrated from 10 plots where field-based assessment
was carried out. Rasters representing positive and negative scores for each input variable were integrated in a ruleset that exactly follows the Hungarian Natura 2000 assessment
scheme for grasslands. Accuracy of each parameter and the final conservation status score
and category was evaluated by 10 independent assessment plots. We conclude that ALS is
a suitable data source for Natura 2000 assessments in grasslands, and that the national
grassland assessment scheme can successfully be used as a GIS processing model for
conservation status, ensuring that the output is directly comparable with traditional field
based assessments.
Airborne lidar is a remote sensing method commonly
used for mapping surface topography in high re... more Airborne lidar is a remote sensing method commonly used for mapping surface topography in high resolution. A water surface in hydrostatic equilibrium theoretically represents a gravity potential isosurface. Here we compare lidar-based ellipsoidal water surface height measurements all around the shore of a major lake with a local high-resolution quasi-geoid model. The ellipsoidal heights of the 87 km2 we sampled all around the shore of the 597 km2 lake surface vary by 0.8m and strong spatial correlation with the quasi-geoid undulation was calculated (R2 = 0.91). After subtraction of the local geoid undulation from the measured ellipsoidal water surface heights, their variation was considerably reduced. Based on a network of water gauge measurements, dynamic water surface heights were also successfully corrected for. This demonstrates that the water surface heights of the lake were truly determined by the local gravity potential.We conclude that both the level of hydrostatic equilibrium of the lake and the accuracy of airborne lidar were sufficient for identifying the spatial variations of gravity potential.
Habitat quality is the ability of the environment to provide conditions appropriate
for individua... more Habitat quality is the ability of the environment to provide conditions appropriate for individual and species persistence. Measuring or monitoring habitat quality requires complex integration of many properties of the ecosystem, where traditional terrestrial data collection methods have proven extremely time-demanding. Remote sensing has known potential to map various ecosystem properties, also allowing rigorous checking of accuracy and supporting standardized processing. Our Special Issue presents examples where remote sensing has been successfully used for habitat mapping, quantification of habitat quality parameters, or multi-parameter modelling of habitat quality itself. New frontiers such as bathymetric scanning, grassland vegetation classification and operational use were explored, various new ecological verification methods were introduced and integration with ongoing habitat conservation schemes was demonstrated. These studies show that remote sensing and Geoinformation Science for habitat quality analysis have evolved from isolated experimental studies to an active field of research with a dedicated community. It is expected that these new methods will substantially contribute to biodiversity conservation worldwide.
Monitoring of lakeshore ecosystems requires fine-scale information to account for the high biodi... more Monitoring of lakeshore ecosystems requires fine-scale information to account for the high biodiversity typically encountered in the land-water ecotone. Sentinel-2 is a satellite with high spatial and spectral resolution and improved revisiting frequency and is expected to have significant potential for habitat mapping and classification of complex lakeshore ecosystems. In this context, investigations of the capabilities of Sentinel-2 in regard to the spatial and spectral dimensions are needed to assess its potential and the quality of the expected output. This study presents the first simulation of the high spatial resolution (i.e., 10 m and 20 m) bands of Sentinel-2 for lakeshore mapping, based on the satellite’s Spectral Response Function and hyperspectral airborne data collected over Lake Balaton, Hungary in August 2010. A comparison of supervised classifications of the simulated products is presented and the information loss from spectral aggregation and spatial upscaling in the context of lakeshore vegetation classification is discussed. We conclude that Sentinel-2 imagery has a strong potential for monitoring fine-scale habitats, such as reed beds.
The geoid is the theoretical model of the Earth, defined as an equipotential surface. Typically i... more The geoid is the theoretical model of the Earth, defined as an equipotential surface. Typically it corresponds to a mean ocean surface and is extended through the continents. Elevations are measured above “sea level” based on the fact that the surface of water in equilibrium closely follows this equipotential surface. On dry land, the geoid can be determined from gravimetric measurements, and interpolation methods are used to represent variations of gravity in a regular grid model. For practical reasons, these are represented as geoid ...
Palmer, S.C.J., Pelevin, V.V., Goncharenko, I., Kovács, A.W., Zlinszky, A., Présing, M., Horvát... more Palmer, S.C.J., Pelevin, V.V., Goncharenko, I., Kovács, A.W., Zlinszky, A., Présing, M., Horváth, H., Nicolás-Perea, V., Balzter, H. and Tóth, V.R. (2013): Ultraviolet Fluorescence LiDAR (UFL) as a robust measurement tool for water quality parameters in turbid lake conditions, Remote Sensing 5, 4405-4422; doi:10.3390/rs5094405, http://hdl.handle.net/2381/28884
The hydrology of Lake Balaton, the largest lake in Central Europe has a long history of human imp... more The hydrology of Lake Balaton, the largest lake in Central Europe has a long history of human impact, which probably started in prehistoric times through agricultural expansion. The most important change in the water regime of the Lake is considered to be the opening of the Sió Canal in 1863. This resulted in the lowering of the average water level
Outlining patches dominated by different plants in wetland vegetation provides
information on spe... more Outlining patches dominated by different plants in wetland vegetation provides information on species succession, microhabitat patterns, wetland health and ecosystem services. Aerial photogrammetry and hyperspectral imaging are the usual data acquisition methods but the application of airborne laser scanning (ALS) as a standalone tool also holds promises for this field since it can be used to quantify 3-dimensional vegetation structure. Lake Balaton is a large shallow lake in western Hungary with shore wetlands that have been in decline since the 1970s. In August 2010, an ALS survey of the shores of Lake Balaton was completed with 1 pt/m2 discrete echo recording. The resulting ALS dataset was processed to several output rasters describing vegetation and terrain properties, creating a sufficient number of independent variables for each raster cell to allow for basic multivariate classification. An expert-generated decision tree algorithm was applied to outline wetland areas, and within these, patches dominated by Typha sp. Carex sp., and Phragmites australis. Reed health was mapped into four categories: healthy, stressed, ruderal and die-back. The output map was tested against a set of 775 geo-tagged ground photographs and had a user’s accuracy of >97% for detecting non-wetland features (trees, artificial surfaces and low density Scirpus stands), >72% for dominant genus detection and >80% for most reed health categories (with 62% for one category). Overall classification accuracy was 82.5%, Cohen’s Kappa 0.80, which is similar to some hyperspectral or multispectral-ALS fusion studies. Compared to hyperspectral imaging, the processing chain of ALS can be automated in a similar way but relies directly on differences in vegetation structure and actively sensed reflectance and is thus probably more robust. The data acquisition parameters are similar to the national surveys of several European countries, suggesting that these existing datasets could be used for vegetation mapping and monitoring.
Socio-hydrology is the science of human influence
on hydrology and the influence of the water cyc... more Socio-hydrology is the science of human influence on hydrology and the influence of the water cycle on human social systems. This newly emerging discipline inherently involves a historic perspective, often focusing on timescales of several centuries. While data on human history is typically available for this time frame, gathering information on the hydrological situation during such a period can prove difficult: measured hydrological data for such long periods are rare, while models and secondary data sets from geomorphology, pedology or archaeology are typically not accurate enough over such a short time. In the first part of this study, the use of historic maps in hydrology is reviewed. Major breakthroughs were the acceptance of historic map content as valid data, the use of preserved features for investigating situations earlier than the map, and the onset of digital georeferencing and data integration. Historic maps can be primary quantitative sources of hydro-geomorphological information, they can provide a context for point-based measurements over larger areas, and they can deliver time series for a better understanding of change scenarios. In the second part, a case study is presented: water level fluctuations of Lake Balaton were reconstructed from maps, levelling logs and other documents. An 18th century map system of the whole 5700 km2 catchment was georeferenced, integrated with two 19th century map systems, and wetlands, forests and open water digitized. Changes in wetland area were compared with lake water level changes in a 220 yr time series. Historic maps show that the water level of the lake was closer to present-day levels than expected, and that wetland loss pre-dates drainage of the lake. The present and future role of historic maps is discussed. Historic hydrological data has to be treated with caution: while it is possible to learn form the past, the assumption that future changes will be like past changes does not always hold. Nevertheless, old maps are relatively accessible data sets and the knowledge base for using them is rapidly growing, and it can be expected that long-term time series will be established by integrating georeferenced map systems over large areas. In the Appendix, a step-by-step guide to using historic maps in hydrology is given, starting from finding a map, through georeferencing and processing the map to publication of the results.
There is increasing demand for reliable, high-resolution vegetation maps
covering large areas. Ai... more There is increasing demand for reliable, high-resolution vegetation maps covering large areas. Airborne laser scanning data is available for large areas with high resolution and supports automatic processing, therefore, it is well suited for habitat mapping. Lowland hay meadows are widespread habitat types in European grasslands, and also have one of the highest species richness. The objective of this study was to test the applicability of airborne laser scanning for vegetation mapping of different grasslands, including the Natura 2000 habitat type lowland hay meadows. Full waveform leaf-on and leaf-off point clouds were collected from a Natura 2000 site in Sopron, Hungary, covering several grasslands. The LIDAR data were processed to a set of rasters representing point attributes including reflectance, echo width, vegetation height, canopy openness, and surface roughness measures, and these were fused to a multi-band pseudo-image. Random forest machine learning was used for classifying this dataset. Habitat type, dominant plant species and other features of interest were noted in a set of 140 field plots. Two sets of categories were used: five classes focusing on meadow identification and the location of lowland hay meadows, and 10 classes, including eight different grassland vegetation categories. For five classes, an overall accuracy of 75% was reached, for 10 classes, this was 68%. The method delivers unprecedented fine resolution vegetation maps for management and ecological research. We conclude that high-resolution full-waveform LIDAR data can be used to detect grassland vegetation classes relevant for Natura 2000.
Natura 2000 Habitat Conservation Status is currently evaluated based on fieldwork.
However, this... more Natura 2000 Habitat Conservation Status is currently evaluated based on fieldwork.
However, this is proving to be unfeasible over large areas. The use of remote sensing is
increasingly encouraged but covering the full range of ecological variables by such datasets
and ensuring compatibility with the traditional assessment methodology has not been achieved
yet. We aimed to test Airborne Laser Scanning (ALS) as a source for mapping all variables
required by the local official conservation status assessment scheme and to develop
an automated method that calculates Natura 2000 conservation status at 0.5 m raster resolution
for 24 km2 of Pannonic Salt Steppe habitat (code 1530). We used multi-temporal (summer
and winter) ALS point clouds with full-waveform recording and a density of 10 pt/m2.
Some required variables were derived from ALS product rasters; others involved vegetation
classification layers calculated by machine learning and fuzzy categorization. Thresholds
separating favorable and unfavorable values of each variable required by the national
assessment scheme were manually calibrated from 10 plots where field-based assessment
was carried out. Rasters representing positive and negative scores for each input variable were integrated in a ruleset that exactly follows the Hungarian Natura 2000 assessment
scheme for grasslands. Accuracy of each parameter and the final conservation status score
and category was evaluated by 10 independent assessment plots. We conclude that ALS is
a suitable data source for Natura 2000 assessments in grasslands, and that the national
grassland assessment scheme can successfully be used as a GIS processing model for
conservation status, ensuring that the output is directly comparable with traditional field
based assessments.
Airborne lidar is a remote sensing method commonly
used for mapping surface topography in high re... more Airborne lidar is a remote sensing method commonly used for mapping surface topography in high resolution. A water surface in hydrostatic equilibrium theoretically represents a gravity potential isosurface. Here we compare lidar-based ellipsoidal water surface height measurements all around the shore of a major lake with a local high-resolution quasi-geoid model. The ellipsoidal heights of the 87 km2 we sampled all around the shore of the 597 km2 lake surface vary by 0.8m and strong spatial correlation with the quasi-geoid undulation was calculated (R2 = 0.91). After subtraction of the local geoid undulation from the measured ellipsoidal water surface heights, their variation was considerably reduced. Based on a network of water gauge measurements, dynamic water surface heights were also successfully corrected for. This demonstrates that the water surface heights of the lake were truly determined by the local gravity potential.We conclude that both the level of hydrostatic equilibrium of the lake and the accuracy of airborne lidar were sufficient for identifying the spatial variations of gravity potential.
Habitat quality is the ability of the environment to provide conditions appropriate
for individua... more Habitat quality is the ability of the environment to provide conditions appropriate for individual and species persistence. Measuring or monitoring habitat quality requires complex integration of many properties of the ecosystem, where traditional terrestrial data collection methods have proven extremely time-demanding. Remote sensing has known potential to map various ecosystem properties, also allowing rigorous checking of accuracy and supporting standardized processing. Our Special Issue presents examples where remote sensing has been successfully used for habitat mapping, quantification of habitat quality parameters, or multi-parameter modelling of habitat quality itself. New frontiers such as bathymetric scanning, grassland vegetation classification and operational use were explored, various new ecological verification methods were introduced and integration with ongoing habitat conservation schemes was demonstrated. These studies show that remote sensing and Geoinformation Science for habitat quality analysis have evolved from isolated experimental studies to an active field of research with a dedicated community. It is expected that these new methods will substantially contribute to biodiversity conservation worldwide.
Monitoring of lakeshore ecosystems requires fine-scale information to account for the high biodi... more Monitoring of lakeshore ecosystems requires fine-scale information to account for the high biodiversity typically encountered in the land-water ecotone. Sentinel-2 is a satellite with high spatial and spectral resolution and improved revisiting frequency and is expected to have significant potential for habitat mapping and classification of complex lakeshore ecosystems. In this context, investigations of the capabilities of Sentinel-2 in regard to the spatial and spectral dimensions are needed to assess its potential and the quality of the expected output. This study presents the first simulation of the high spatial resolution (i.e., 10 m and 20 m) bands of Sentinel-2 for lakeshore mapping, based on the satellite’s Spectral Response Function and hyperspectral airborne data collected over Lake Balaton, Hungary in August 2010. A comparison of supervised classifications of the simulated products is presented and the information loss from spectral aggregation and spatial upscaling in the context of lakeshore vegetation classification is discussed. We conclude that Sentinel-2 imagery has a strong potential for monitoring fine-scale habitats, such as reed beds.
The geoid is the theoretical model of the Earth, defined as an equipotential surface. Typically i... more The geoid is the theoretical model of the Earth, defined as an equipotential surface. Typically it corresponds to a mean ocean surface and is extended through the continents. Elevations are measured above “sea level” based on the fact that the surface of water in equilibrium closely follows this equipotential surface. On dry land, the geoid can be determined from gravimetric measurements, and interpolation methods are used to represent variations of gravity in a regular grid model. For practical reasons, these are represented as geoid ...
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information on species succession, microhabitat patterns, wetland health and ecosystem
services. Aerial photogrammetry and hyperspectral imaging are the usual data acquisition
methods but the application of airborne laser scanning (ALS) as a standalone tool also
holds promises for this field since it can be used to quantify 3-dimensional vegetation
structure. Lake Balaton is a large shallow lake in western Hungary with shore wetlands that
have been in decline since the 1970s. In August 2010, an ALS survey of the shores of Lake
Balaton was completed with 1 pt/m2 discrete echo recording. The resulting ALS dataset
was processed to several output rasters describing vegetation and terrain properties,
creating a sufficient number of independent variables for each raster cell to allow for basic
multivariate classification. An expert-generated decision tree algorithm was applied to
outline wetland areas, and within these, patches dominated by Typha sp. Carex sp., and
Phragmites australis. Reed health was mapped into four categories: healthy, stressed,
ruderal and die-back. The output map was tested against a set of 775 geo-tagged ground
photographs and had a user’s accuracy of >97% for detecting non-wetland features (trees,
artificial surfaces and low density Scirpus stands), >72% for dominant genus detection and
>80% for most reed health categories (with 62% for one category). Overall classification accuracy was 82.5%, Cohen’s Kappa 0.80, which is similar to some hyperspectral or
multispectral-ALS fusion studies. Compared to hyperspectral imaging, the processing
chain of ALS can be automated in a similar way but relies directly on differences in
vegetation structure and actively sensed reflectance and is thus probably more robust. The
data acquisition parameters are similar to the national surveys of several European
countries, suggesting that these existing datasets could be used for vegetation mapping
and monitoring.
on hydrology and the influence of the water cycle on human
social systems. This newly emerging discipline inherently involves
a historic perspective, often focusing on timescales of
several centuries. While data on human history is typically
available for this time frame, gathering information on the
hydrological situation during such a period can prove difficult:
measured hydrological data for such long periods are
rare, while models and secondary data sets from geomorphology,
pedology or archaeology are typically not accurate
enough over such a short time. In the first part of this study,
the use of historic maps in hydrology is reviewed. Major
breakthroughs were the acceptance of historic map content
as valid data, the use of preserved features for investigating
situations earlier than the map, and the onset of digital georeferencing
and data integration. Historic maps can be primary
quantitative sources of hydro-geomorphological information,
they can provide a context for point-based measurements
over larger areas, and they can deliver time series for
a better understanding of change scenarios.
In the second part, a case study is presented: water level
fluctuations of Lake Balaton were reconstructed from maps,
levelling logs and other documents. An 18th century map
system of the whole 5700 km2 catchment was georeferenced,
integrated with two 19th century map systems, and wetlands,
forests and open water digitized. Changes in wetland area
were compared with lake water level changes in a 220 yr time
series. Historic maps show that the water level of the lake was
closer to present-day levels than expected, and that wetland
loss pre-dates drainage of the lake.
The present and future role of historic maps is discussed.
Historic hydrological data has to be treated with caution:
while it is possible to learn form the past, the assumption
that future changes will be like past changes does not always
hold. Nevertheless, old maps are relatively accessible data
sets and the knowledge base for using them is rapidly growing,
and it can be expected that long-term time series will be
established by integrating georeferenced map systems over
large areas.
In the Appendix, a step-by-step guide to using historic
maps in hydrology is given, starting from finding a map,
through georeferencing and processing the map to publication
of the results.
covering large areas. Airborne laser scanning data is available for large areas with high
resolution and supports automatic processing, therefore, it is well suited for habitat
mapping. Lowland hay meadows are widespread habitat types in European grasslands, and
also have one of the highest species richness. The objective of this study was to test the
applicability of airborne laser scanning for vegetation mapping of different grasslands,
including the Natura 2000 habitat type lowland hay meadows. Full waveform leaf-on and
leaf-off point clouds were collected from a Natura 2000 site in Sopron, Hungary, covering several grasslands. The LIDAR data were processed to a set of rasters representing point
attributes including reflectance, echo width, vegetation height, canopy openness, and
surface roughness measures, and these were fused to a multi-band pseudo-image. Random
forest machine learning was used for classifying this dataset. Habitat type, dominant plant
species and other features of interest were noted in a set of 140 field plots. Two sets of
categories were used: five classes focusing on meadow identification and the location of
lowland hay meadows, and 10 classes, including eight different grassland vegetation
categories. For five classes, an overall accuracy of 75% was reached, for 10 classes, this
was 68%. The method delivers unprecedented fine resolution vegetation maps for
management and ecological research. We conclude that high-resolution full-waveform
LIDAR data can be used to detect grassland vegetation classes relevant for Natura 2000.
However, this is proving to be unfeasible over large areas. The use of remote sensing is
increasingly encouraged but covering the full range of ecological variables by such datasets
and ensuring compatibility with the traditional assessment methodology has not been achieved
yet. We aimed to test Airborne Laser Scanning (ALS) as a source for mapping all variables
required by the local official conservation status assessment scheme and to develop
an automated method that calculates Natura 2000 conservation status at 0.5 m raster resolution
for 24 km2 of Pannonic Salt Steppe habitat (code 1530). We used multi-temporal (summer
and winter) ALS point clouds with full-waveform recording and a density of 10 pt/m2.
Some required variables were derived from ALS product rasters; others involved vegetation
classification layers calculated by machine learning and fuzzy categorization. Thresholds
separating favorable and unfavorable values of each variable required by the national
assessment scheme were manually calibrated from 10 plots where field-based assessment
was carried out. Rasters representing positive and negative scores for each input variable were integrated in a ruleset that exactly follows the Hungarian Natura 2000 assessment
scheme for grasslands. Accuracy of each parameter and the final conservation status score
and category was evaluated by 10 independent assessment plots. We conclude that ALS is
a suitable data source for Natura 2000 assessments in grasslands, and that the national
grassland assessment scheme can successfully be used as a GIS processing model for
conservation status, ensuring that the output is directly comparable with traditional field
based assessments.
used for mapping surface topography in high resolution.
A water surface in hydrostatic equilibrium theoretically
represents a gravity potential isosurface. Here we compare
lidar-based ellipsoidal water surface height measurements all
around the shore of a major lake with a local high-resolution
quasi-geoid model. The ellipsoidal heights of the 87 km2 we
sampled all around the shore of the 597 km2 lake surface vary
by 0.8m and strong spatial correlation with the quasi-geoid
undulation was calculated (R2 = 0.91). After subtraction of
the local geoid undulation from the measured ellipsoidal water
surface heights, their variation was considerably reduced.
Based on a network of water gauge measurements, dynamic
water surface heights were also successfully corrected for.
This demonstrates that the water surface heights of the lake
were truly determined by the local gravity potential.We conclude
that both the level of hydrostatic equilibrium of the lake
and the accuracy of airborne lidar were sufficient for identifying
the spatial variations of gravity potential.
for individual and species persistence. Measuring or monitoring habitat quality requires
complex integration of many properties of the ecosystem, where traditional terrestrial data
collection methods have proven extremely time-demanding. Remote sensing has known
potential to map various ecosystem properties, also allowing rigorous checking of accuracy
and supporting standardized processing. Our Special Issue presents examples where remote
sensing has been successfully used for habitat mapping, quantification of habitat quality
parameters, or multi-parameter modelling of habitat quality itself. New frontiers such as
bathymetric scanning, grassland vegetation classification and operational use were explored,
various new ecological verification methods were introduced and integration with ongoing habitat conservation schemes was demonstrated. These studies show that remote sensing and
Geoinformation Science for habitat quality analysis have evolved from isolated experimental
studies to an active field of research with a dedicated community. It is expected that these
new methods will substantially contribute to biodiversity conservation worldwide.
information on species succession, microhabitat patterns, wetland health and ecosystem
services. Aerial photogrammetry and hyperspectral imaging are the usual data acquisition
methods but the application of airborne laser scanning (ALS) as a standalone tool also
holds promises for this field since it can be used to quantify 3-dimensional vegetation
structure. Lake Balaton is a large shallow lake in western Hungary with shore wetlands that
have been in decline since the 1970s. In August 2010, an ALS survey of the shores of Lake
Balaton was completed with 1 pt/m2 discrete echo recording. The resulting ALS dataset
was processed to several output rasters describing vegetation and terrain properties,
creating a sufficient number of independent variables for each raster cell to allow for basic
multivariate classification. An expert-generated decision tree algorithm was applied to
outline wetland areas, and within these, patches dominated by Typha sp. Carex sp., and
Phragmites australis. Reed health was mapped into four categories: healthy, stressed,
ruderal and die-back. The output map was tested against a set of 775 geo-tagged ground
photographs and had a user’s accuracy of >97% for detecting non-wetland features (trees,
artificial surfaces and low density Scirpus stands), >72% for dominant genus detection and
>80% for most reed health categories (with 62% for one category). Overall classification accuracy was 82.5%, Cohen’s Kappa 0.80, which is similar to some hyperspectral or
multispectral-ALS fusion studies. Compared to hyperspectral imaging, the processing
chain of ALS can be automated in a similar way but relies directly on differences in
vegetation structure and actively sensed reflectance and is thus probably more robust. The
data acquisition parameters are similar to the national surveys of several European
countries, suggesting that these existing datasets could be used for vegetation mapping
and monitoring.
on hydrology and the influence of the water cycle on human
social systems. This newly emerging discipline inherently involves
a historic perspective, often focusing on timescales of
several centuries. While data on human history is typically
available for this time frame, gathering information on the
hydrological situation during such a period can prove difficult:
measured hydrological data for such long periods are
rare, while models and secondary data sets from geomorphology,
pedology or archaeology are typically not accurate
enough over such a short time. In the first part of this study,
the use of historic maps in hydrology is reviewed. Major
breakthroughs were the acceptance of historic map content
as valid data, the use of preserved features for investigating
situations earlier than the map, and the onset of digital georeferencing
and data integration. Historic maps can be primary
quantitative sources of hydro-geomorphological information,
they can provide a context for point-based measurements
over larger areas, and they can deliver time series for
a better understanding of change scenarios.
In the second part, a case study is presented: water level
fluctuations of Lake Balaton were reconstructed from maps,
levelling logs and other documents. An 18th century map
system of the whole 5700 km2 catchment was georeferenced,
integrated with two 19th century map systems, and wetlands,
forests and open water digitized. Changes in wetland area
were compared with lake water level changes in a 220 yr time
series. Historic maps show that the water level of the lake was
closer to present-day levels than expected, and that wetland
loss pre-dates drainage of the lake.
The present and future role of historic maps is discussed.
Historic hydrological data has to be treated with caution:
while it is possible to learn form the past, the assumption
that future changes will be like past changes does not always
hold. Nevertheless, old maps are relatively accessible data
sets and the knowledge base for using them is rapidly growing,
and it can be expected that long-term time series will be
established by integrating georeferenced map systems over
large areas.
In the Appendix, a step-by-step guide to using historic
maps in hydrology is given, starting from finding a map,
through georeferencing and processing the map to publication
of the results.
covering large areas. Airborne laser scanning data is available for large areas with high
resolution and supports automatic processing, therefore, it is well suited for habitat
mapping. Lowland hay meadows are widespread habitat types in European grasslands, and
also have one of the highest species richness. The objective of this study was to test the
applicability of airborne laser scanning for vegetation mapping of different grasslands,
including the Natura 2000 habitat type lowland hay meadows. Full waveform leaf-on and
leaf-off point clouds were collected from a Natura 2000 site in Sopron, Hungary, covering several grasslands. The LIDAR data were processed to a set of rasters representing point
attributes including reflectance, echo width, vegetation height, canopy openness, and
surface roughness measures, and these were fused to a multi-band pseudo-image. Random
forest machine learning was used for classifying this dataset. Habitat type, dominant plant
species and other features of interest were noted in a set of 140 field plots. Two sets of
categories were used: five classes focusing on meadow identification and the location of
lowland hay meadows, and 10 classes, including eight different grassland vegetation
categories. For five classes, an overall accuracy of 75% was reached, for 10 classes, this
was 68%. The method delivers unprecedented fine resolution vegetation maps for
management and ecological research. We conclude that high-resolution full-waveform
LIDAR data can be used to detect grassland vegetation classes relevant for Natura 2000.
However, this is proving to be unfeasible over large areas. The use of remote sensing is
increasingly encouraged but covering the full range of ecological variables by such datasets
and ensuring compatibility with the traditional assessment methodology has not been achieved
yet. We aimed to test Airborne Laser Scanning (ALS) as a source for mapping all variables
required by the local official conservation status assessment scheme and to develop
an automated method that calculates Natura 2000 conservation status at 0.5 m raster resolution
for 24 km2 of Pannonic Salt Steppe habitat (code 1530). We used multi-temporal (summer
and winter) ALS point clouds with full-waveform recording and a density of 10 pt/m2.
Some required variables were derived from ALS product rasters; others involved vegetation
classification layers calculated by machine learning and fuzzy categorization. Thresholds
separating favorable and unfavorable values of each variable required by the national
assessment scheme were manually calibrated from 10 plots where field-based assessment
was carried out. Rasters representing positive and negative scores for each input variable were integrated in a ruleset that exactly follows the Hungarian Natura 2000 assessment
scheme for grasslands. Accuracy of each parameter and the final conservation status score
and category was evaluated by 10 independent assessment plots. We conclude that ALS is
a suitable data source for Natura 2000 assessments in grasslands, and that the national
grassland assessment scheme can successfully be used as a GIS processing model for
conservation status, ensuring that the output is directly comparable with traditional field
based assessments.
used for mapping surface topography in high resolution.
A water surface in hydrostatic equilibrium theoretically
represents a gravity potential isosurface. Here we compare
lidar-based ellipsoidal water surface height measurements all
around the shore of a major lake with a local high-resolution
quasi-geoid model. The ellipsoidal heights of the 87 km2 we
sampled all around the shore of the 597 km2 lake surface vary
by 0.8m and strong spatial correlation with the quasi-geoid
undulation was calculated (R2 = 0.91). After subtraction of
the local geoid undulation from the measured ellipsoidal water
surface heights, their variation was considerably reduced.
Based on a network of water gauge measurements, dynamic
water surface heights were also successfully corrected for.
This demonstrates that the water surface heights of the lake
were truly determined by the local gravity potential.We conclude
that both the level of hydrostatic equilibrium of the lake
and the accuracy of airborne lidar were sufficient for identifying
the spatial variations of gravity potential.
for individual and species persistence. Measuring or monitoring habitat quality requires
complex integration of many properties of the ecosystem, where traditional terrestrial data
collection methods have proven extremely time-demanding. Remote sensing has known
potential to map various ecosystem properties, also allowing rigorous checking of accuracy
and supporting standardized processing. Our Special Issue presents examples where remote
sensing has been successfully used for habitat mapping, quantification of habitat quality
parameters, or multi-parameter modelling of habitat quality itself. New frontiers such as
bathymetric scanning, grassland vegetation classification and operational use were explored,
various new ecological verification methods were introduced and integration with ongoing habitat conservation schemes was demonstrated. These studies show that remote sensing and
Geoinformation Science for habitat quality analysis have evolved from isolated experimental
studies to an active field of research with a dedicated community. It is expected that these
new methods will substantially contribute to biodiversity conservation worldwide.