I am interested in developing and taking advantage of remotely sensed data to monitor glaciers, icecaps, and ice sheets. Supervisors: Ted Scambos and Gareth Rees
Glaciers are key to understanding the world's hydrological cycle as well as regional and global c... more Glaciers are key to understanding the world's hydrological cycle as well as regional and global climate change. Glacier surfaces metamorphose into a range of zones which have implications for surface energy balance and can be used as a proxy for a glacier's mass balance. Multispectral images (in particular Landsat data) have been extensively used to classify and study glacier surfaces. This study uses full-spectrum in situ surface reflectance data from Midtre Lovénbreen (Svalbard) and Langjökull (Iceland) which are combined with Landsat ETM+ imagery to inform and explore glacier surface classification.
Deriving glacier outlines from satellite data has become increasingly popular in the past decade.... more Deriving glacier outlines from satellite data has become increasingly popular in the past decade. In particular when glacier outlines are used as a base for change assessment, it is important to know how accurate they are. Calculating the accuracy correctly is challenging, as appropriate reference data (e.g. from higher-resolution sensors) are seldom available. Moreover, after the required manual correction of the raw outlines (e.g. for debris cover), such a comparison would only reveal the accuracy of the analyst rather than of the algorithm applied. Here we compare outlines for clean and debriscovered glaciers, as derived from single and multiple digitizing by different or the same analysts on very high-(1 m) and medium-resolution (30 m) remote-sensing data, against each other and to glacier outlines derived from automated classification of Landsat Thematic Mapper data. Results show a high variability in the interpretation of debris-covered glacier parts, largely independent of the spatial resolution (area differences were up to 30%), and an overall good agreement for clean ice with sufficient contrast to the surrounding terrain (differences $5%). The differences of the automatically derived outlines from a reference value are as small as the standard deviation of the manual digitizations from several analysts. Based on these results, we conclude that automated mapping of clean ice is preferable to manual digitization and recommend using the latter method only for required corrections of incorrectly mapped glacier parts (e.g. debris cover, shadow).
Abstract Three independent data sets are combined to produce a 30m-resolution digital elevation m... more Abstract Three independent data sets are combined to produce a 30m-resolution digital elevation model (DEM) of Langj��kull, Iceland's second largest icecap (~ 950 km2) for 2007. The data are from: i) an airborne LiDAR survey; ii) skidoo-mounted GPS; and iii) Landsat ETM+ band 4. The technique of photoclinometry (which calculates slope angles and aspects from visible imagery) is applied to the Landsat data, which is then integrated to produce interpolated elevation data between the LiDAR flight lines and the GPS skidoo tracks. It is ...
34 One of synthesis activities (although both short in time and thematic) could be implemented wi... more 34 One of synthesis activities (although both short in time and thematic) could be implemented within discussions undertaken within this meeting. The discussion will focus several questions such as: 1. What changes in natural environment (ecosystems) in taiga-tundra interface ...
Glaciers are key to understanding the world's hydrological cycle as well as regional and global c... more Glaciers are key to understanding the world's hydrological cycle as well as regional and global climate change. Glacier surfaces metamorphose into a range of zones which have implications for surface energy balance and can be used as a proxy for a glacier's mass balance. Multispectral images (in particular Landsat data) have been extensively used to classify and study glacier surfaces. This study uses full-spectrum in situ surface reflectance data from Midtre Lovénbreen (Svalbard) and Langjökull (Iceland) which are combined with Landsat ETM+ imagery to inform and explore glacier surface classification.
Deriving glacier outlines from satellite data has become increasingly popular in the past decade.... more Deriving glacier outlines from satellite data has become increasingly popular in the past decade. In particular when glacier outlines are used as a base for change assessment, it is important to know how accurate they are. Calculating the accuracy correctly is challenging, as appropriate reference data (e.g. from higher-resolution sensors) are seldom available. Moreover, after the required manual correction of the raw outlines (e.g. for debris cover), such a comparison would only reveal the accuracy of the analyst rather than of the algorithm applied. Here we compare outlines for clean and debriscovered glaciers, as derived from single and multiple digitizing by different or the same analysts on very high-(1 m) and medium-resolution (30 m) remote-sensing data, against each other and to glacier outlines derived from automated classification of Landsat Thematic Mapper data. Results show a high variability in the interpretation of debris-covered glacier parts, largely independent of the spatial resolution (area differences were up to 30%), and an overall good agreement for clean ice with sufficient contrast to the surrounding terrain (differences $5%). The differences of the automatically derived outlines from a reference value are as small as the standard deviation of the manual digitizations from several analysts. Based on these results, we conclude that automated mapping of clean ice is preferable to manual digitization and recommend using the latter method only for required corrections of incorrectly mapped glacier parts (e.g. debris cover, shadow).
Abstract Three independent data sets are combined to produce a 30m-resolution digital elevation m... more Abstract Three independent data sets are combined to produce a 30m-resolution digital elevation model (DEM) of Langj��kull, Iceland's second largest icecap (~ 950 km2) for 2007. The data are from: i) an airborne LiDAR survey; ii) skidoo-mounted GPS; and iii) Landsat ETM+ band 4. The technique of photoclinometry (which calculates slope angles and aspects from visible imagery) is applied to the Landsat data, which is then integrated to produce interpolated elevation data between the LiDAR flight lines and the GPS skidoo tracks. It is ...
34 One of synthesis activities (although both short in time and thematic) could be implemented wi... more 34 One of synthesis activities (although both short in time and thematic) could be implemented within discussions undertaken within this meeting. The discussion will focus several questions such as: 1. What changes in natural environment (ecosystems) in taiga-tundra interface ...
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