scholarly journals Validation of satellite altimetry by kinematic GNSS in central East Antarctica

2017 ◽  
Vol 11 (3) ◽  
pp. 1111-1130 ◽  
Author(s):  
Ludwig Schröder ◽  
Andreas Richter ◽  
Denis V. Fedorov ◽  
Lutz Eberlein ◽  
Evgeny V. Brovkov ◽  
...  
Keyword(s):  
Satellite Altimetry ◽  
Digital Elevation Models ◽  
Surface Elevation ◽  
Data Sets ◽  
Radar Altimetry ◽  
Independent Evidence ◽  
Ice Surface ◽  
Digital Elevation ◽  
Wide Range ◽  
Elevation Data

Abstract. Ice-surface elevation profiles of more than 30 000 km in total length are derived from kinematic GNSS (GPS and the Russian GLONASS) observations on sledge convoy vehicles along traverses between Vostok Station and the East Antarctic coast. These profiles have accuracies between 4 and 9 cm. They are used to validate elevation data sets from both radar and laser satellite altimetry as well as four digital elevation models. A crossover analysis with three different processing versions of Envisat radar altimetry elevation profiles yields a clear preference for the relocation method over the direct method of slope correction and for threshold retrackers over functional fit algorithms. The validation of CryoSat-2 low-resolution mode and SARIn mode data sets documents the progress made from baseline B to C elevation products. ICESat laser altimetry data are demonstrated to be accurate to a few decimetres over a wide range of surface slopes. A crossover adjustment in the region of subglacial Lake Vostok combining ICESat elevation data with our GNSS profiles yields a new set of ICESat laser campaign biases and provides new, independent evidence for the stability of the ice-surface elevation above the lake. The evaluation of the digital elevation models reveals the benefits of combining laser and radar altimetry.

scholarly journals Validation of satellite altimetry by kinematic GNSS in central East Antarctica

2017 ◽  
Author(s):  
Ludwig Schröder ◽  
Andreas Richter ◽  
Denis V. Fedorov ◽  
Lutz Eberlein ◽  
Evgeny V. Brovkov ◽  
...  
Keyword(s):  
Satellite Altimetry ◽  
Direct Method ◽  
Digital Elevation Models ◽  
Surface Elevation ◽  
Radar Altimetry ◽  
Independent Evidence ◽  
Ice Surface ◽  
Digital Elevation ◽  
Wide Range ◽  
Crossover Analysis

Abstract. Ice-surface elevation profiles of more than 30.000 km in total length are derived from kinematic GNSS observations on sledge convoy vehicles along traverses between Vostok station and the East Antarctic coast. The profiles have accuracies between 4 and 9 cm. They are used to validate elevation datasets from both radar and laser satellite altimetry as well as four digital elevation models. A crossover analysis with three different Envisat radar altimetry datasets yields a clear preference for the relocation method over the direct method of slope correction and for threshold retrackers over functional fit algorithms. The validation of Cryosat-2 low-resolution mode and SARIn mode datasets documents the progress made from baseline B to C elevation products. ICESat laser altimetry data are demonstrated to be accurate to a few decimeters over wide range of surface slopes. A crossover adjustment above subglacial Lake Vostok combining ICESat elevation data with our GNSS profiles yields a new set of ICESat laser campaign biases and provides new, independent evidence for the stability of the ice-surface elevation above the lake. The evaluation of digital elevation models reveals the importance of radar altimetry for the reduction of interpolation errors.

scholarly journals The Greenland Ice Mapping Project (GIMP) land classification and surface elevation data sets

2014 ◽  
Vol 8 (4) ◽  
pp. 1509-1518 ◽  
Author(s):  
I. M. Howat ◽  
A. Negrete ◽  
B. E. Smith
Keyword(s):  
Satellite Altimetry ◽  
Data Sets ◽  
Image Mosaic ◽  
Terrain Classification ◽  
Land Classification ◽  
Registration Error ◽  
Digital Elevation ◽  
Elevation Data ◽  
Landsat 7 ◽  
Elevation Model

Abstract. As part of the Greenland Ice Mapping Project (GIMP) we have produced three geospatial data sets for the entire ice sheet and periphery. These are (1) a complete, 15 m resolution image mosaic, (2) ice-covered and ice-free terrain classification masks, also posted to 15 m resolution, and (3) a complete, altimeter-registered digital elevation model posted at 30 m. The image mosaic was created from a combination of Landsat-7 and RADARSAT-1 imagery acquired between 1999 and 2002. Each pixel in the image is stamped with the acquisition date and geo-registration error to facilitate change detection. This mosaic was then used to manually produce complete ice-covered and ice-free land classification masks. Finally, we used satellite altimetry and stereo-photogrammetric digital elevation models (DEMs) to enhance an existing DEM for Greenland, substantially improving resolution and accuracy over the ice margin and periphery.

scholarly journals ON GENERATING DIGITAL ELEVATION MODELS FROM LIDAR DATA – RESOLUTION VERSUS ACCURACY AND TOPOGRAPHIC WETNESS INDEX INDICES IN NORTHERN PEATLANDS

2012 ◽  
Vol 38 (2) ◽  
pp. 57-69 ◽  
Author(s):  
Abdulghani Hasan ◽  
Petter Pilesjö ◽  
Andreas Persson
Keyword(s):  
Large Scale ◽  
Drainage Area ◽  
Data Sets ◽  
Topographic Wetness Index ◽  
Absolute Deviation ◽  
Digital Elevation ◽  
Elevation Data ◽  
Scale Modelling ◽  
Data Points ◽  
Emission Modelling

Global change and GHG emission modelling are dependent on accurate wetness estimations for predictions of e.g. methane emissions. This study aims to quantify how the slope, drainage area and the TWI vary with the resolution of DEMs for a flat peatland area. Six DEMs with spatial resolutions from 0.5 to 90 m were interpolated with four different search radiuses. The relationship between accuracy of the DEM and the slope was tested. The LiDAR elevation data was divided into two data sets. The number of data points facilitated an evaluation dataset with data points not more than 10 mm away from the cell centre points in the interpolation dataset. The DEM was evaluated using a quantile-quantile test and the normalized median absolute deviation. It showed independence of the resolution when using the same search radius. The accuracy of the estimated elevation for different slopes was tested using the 0.5 meter DEM and it showed a higher deviation from evaluation data for steep areas. The slope estimations between resolutions showed differences with values that exceeded 50%. Drainage areas were tested for three resolutions, with coinciding evaluation points. The model ability to generate drainage area at each resolution was tested by pair wise comparison of three data subsets and showed differences of more than 50% in 25% of the evaluated points. The results show that consideration of DEM resolution is a necessity for the use of slope, drainage area and TWI data in large scale modelling.

Collocated OLCI optical imagery and SAR radar altimetry from Sentinel3 for enhanced sea ice surface classification

2021 ◽  
Author(s):  
Dorsa Nasrollahi Shirazi ◽  
Michel Tsamados ◽  
Isobel Lawrence ◽  
Sanggyun Lee ◽  
Thomas Johnson ◽  
...  
Keyword(s):  
Sea Ice ◽  
Classification Algorithms ◽  
Polar Regions ◽  
Radar Altimetry ◽  
Imaging Spectrometer ◽  
Ice Surface ◽  
Ice Roughness ◽  
Elevation Data ◽  
Optical Imagery ◽  
Surface Classification

<p>The Copernicus operational Sentinel-3A since February 2016 and Sentinel-3B since April 2018 build on the CryoSat-2 legacy in terms of their synthetic aperture radar (SAR) mode altimetry providing high-resolution radar freeboard elevation data over the polar regions up to 81N. This technology combined with the Ocean and Land Colour Instrument (OLCI) imaging spectrometer offers the first space-time collocated optical imagery and radar altimetry dataset. We use these joint datasets for validation of several existing surface classification algorithms based on Sentinel-3 altimeter echo shapes. We also explore the potential for novel AI techniques such as convolutional neural networks (CNN) for winter and summer sea ice surface classification (i.e. melt pond fraction, lead fraction, sea ice roughness). For lead surface classification we analyse the winters of 2018/19 and 2019/20 and for summer sea ice feature classification we focus on the Sentinel-3A &3B tandem phase of the summer 2018. We compare our CNN models with other existing surface classification algorithms.</p>

scholarly journals COMPARATIVE ANALYSIS FOR METHODS OF BUILDING DIGITAL ELEVATION MODELS FROM TOPOGRAPHIC MAPS USING GEOINFORMATION TECHNOLOGIES

2021 ◽  
Vol 47 (4) ◽  
pp. 191-199
Author(s):  
Vadim Belenok ◽  
Yuriy Velikodsky ◽  
Oleksandr Nikolaienko ◽  
Nataliia Rul ◽  
Sergiy Kryachok ◽  
...  
Keyword(s):  
Digital Elevation Models ◽  
Complex Structure ◽  
Topographic Maps ◽  
Interpolation Methods ◽  
Contour Lines ◽  
Central Russian Upland ◽  
Digital Elevation ◽  
Elevation Data ◽  
The Russian Federation ◽  
Elevation Model

The article considers the question of estimating the accuracy of interpolation methods for building digital elevation models using Soviet topographic maps. The territory of the Kursk region of the Russian Federation was used as the study area, because it is located on the Central Russian Upland and characterized by the complex structure of the vertical and horizontal dissection of the relief. Contour lines automatically obtained using a Python algorithm were used as the initial elevation data to build a digital elevation model. Digital elevation models obtained by thirteen different interpolation methods in ArcGIS and Surfer software were built and analyzed. Special attention is paid to the ANUDEM method, which allows to obtain hydrologically correct digital elevation models. Recommendations for the use of one or another method of interpolation are given. The results can be useful for professionals who use topographic maps in their work and deals with the design using digital elevation models.

scholarly journals High-resolution inventory to capture glacier disintegration in the Austrian Silvretta

2021 ◽  
Author(s):  
Andrea Fischer ◽  
Bernd Seiser ◽  
Kay Helfricht ◽  
Martin Stocker-Waldhuber
Keyword(s):  
High Resolution ◽  
Spatial Resolution ◽  
Ice Age ◽  
Surface Elevation ◽  
Glacier Changes ◽  
Wide Range ◽  
Elevation Data ◽  
Glacier Ice ◽  
Geodetic Mass Balance

Abstract. Eastern Alpine glaciers have been receding since the LIA maximum, but the majority of glacier margins could be delineated unambiguously for the last Austrian glacier inventories. Even debris-covered termini, changes in slope, colour or the position of englacial streams enabled at least an in situ survey of glacier outlines. Today the outlines of totally debris-covered glacier ice are fuzzy and raise the theoretical discussion if these glaciogenic features are still glaciers and should be part of the respective inventory – or part of an inventory of transient cryogenic landforms. A new high-resolution glacier inventory (area and surface elevation) was compiled for the years 2017 and 2018 to quantify glacier changes for the Austrian Silvretta region in full. Glacier outlines were mapped manually, based on orthophotos and elevation models and patterns of volume change of 1 to 0.5 m spatial resolution. The vertical accuracy of the DEMs generated from 6 to 8 LiDAR points per m2 is in the order of centimetres. calculated in relation to the previous inventories dating from 2004/2006 (LiDAR), 2002, 1969 (photogrammetry) and to the Little Ice Age maximum extent (moraines). Between 2004/06 and 2017/2018, the 46 glaciers of the Austrian Silvretta lost −29 ± 4 % of their area and now cover 13.1 ± 0.4 km2. This is only 32 ± 2 % of their LIA extent of 40.9 ± 4.1 km2. The area change rate increased from −0.6 %/year (1969–2002) to −2.4 %/year (2004/06–2017/18). The annual geodetic mass balance showed a loss increasing from −0.2 ± 0.1 m w.e./year (1969–2002) to –0.8 m ±0.1 w.e./year (2004/06–2017/18) with an interim peak in 2002–2004/06 at −1.5 ± 0.7 m w.e./year. Identifying the glacier outlines offers a wide range of possible interpretations of former glaciers that have evolved into small and now totally debris-covered cryogenic geomorphological structures. Only the patterns and amounts of volume changes allow us to estimate the area of the buried glacier remnants. To keep track of the buried ice and its fate, and to distinguish increasing debris cover from ice loss, we recommend inventory repeat frequencies of three to five years and surface elevation data with a spatial resolution of one metre.

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