Co-registration and bias corrections of satellite elevation data sets for quantifying glacier thickness change

C Nuth,A Kääb

doi:10.5194/tc-5-271-2011

Abstract

Abstract. There are an increasing number of digital elevation models (DEMs) available worldwide for deriving elevation differences over time, including vertical changes on glaciers. Most of these DEMs are heavily post-processed or merged, so that physical error modelling becomes difficult and statistical error modelling is required instead. We propose a three-step methodological framework for assessing and correcting DEMs to quantify glacier elevation changes: (i) remove DEM shifts, (ii) check for elevation-dependent biases, and (iii) check for higher-order, sensor-specific biases. A simple, analytic and robust method to co-register elevation data is presented in regions where stable terrain is either plentiful (case study New Zealand) or limited (case study Svalbard). The method is demonstrated using the three global elevation data sets available to date, SRTM, ICESat and the ASTER GDEM, and with automatically generated DEMs from satellite stereo instruments of ASTER and SPOT5-HRS. After 3-D co-registration, significant biases related to elevation were found in some of the stereoscopic DEMs. Biases related to the satellite acquisition geometry (along/cross track) were detected at two frequencies in the automatically generated ASTER DEMs. The higher frequency bias seems to be related to satellite jitter, most apparent in the back-looking pass of the satellite. The origins of the more significant lower frequency bias is uncertain. ICESat-derived elevations are found to be the most consistent globally available elevation data set available so far. Before performing regional-scale glacier elevation change studies or mosaicking DEMs from multiple individual tiles (e.g. ASTER GDEM), we recommend to co-register all elevation data to ICESat as a global vertical reference system.

Highlights

Applications of regional and global scale elevation products have increased substantially in geoscience
Franz Josef and Fox glacier are located on the west side of the mountain divide and receive large amounts of accumulation due to the large eastwest precipitation gradient (Fitzharris et al, 1999) and experience high magnitudes of ablation (Anderson et al, 2006)
A 2003 ASTER SilcAst digital elevation models (DEMs) is tested against a 2008 SPOT5HRS DEM from the IPY-SPIRIT Project (Korona et al, 2009), a 1990 aerophotogrammetric DEM from the Norwegian Polar Institute and 2003–2008 ICESat data (Table 4)

Summary

Introduction

Applications of regional and global scale elevation products have increased substantially in geoscience. The third nearly global elevation dataset is the newly released ASTER GDEM based upon a composition of automatically generated DEMs from Advanced Spaceborne Emission and Reflection radiometer (ASTER) stereo scenes acquired from 2000–present (METI/NASA/USGS, 2009). In all of these datasets, errors and biases may persist from sensor instabilities, limitations of the techniques, bad surveying conditions on the ground and post-processing artifacts. The errors occur at a range of scales that directly affect measurement accuracy and precision, and increases the significance level a glacier thickness change requires for adequate detection through elevation differencing

Objectives

Methods

Results

Conclusion