Abstract
A longer temporal scale of Antarctic observations is vital to better understanding glacier dynamics and improving ice sheet model projections. One underutilized data source that expands the temporal scale is aerial photography, specifically imagery collected prior to 1990. However, processing Antarctic historical aerial imagery using modern photogrammetry software is difficult, as it requires precise information about the data collection process and extensive in situ ground control is required. Often, the necessary orientation metadata for older aerial imagery is lost and in situ data collection in regions like Antarctica is extremely difficult to obtain, limiting the use of traditional photogrammetric methods. Here, we test an alternative methodology to generate elevations from historical Antarctic aerial imagery. Instead of relying on pre-existing ground control, we use structure-from-motion photogrammetry techniques to process the imagery with manually derived ground control from high-resolution satellite imagery. This case study is based on vertical aerial image sets collected over Byrd Glacier, East Antarctica in December 1978 and January 1979. Our results are the oldest, highest resolution digital elevation models (DEMs) ever generated for an Antarctic glacier. We use these DEMs to estimate glacier dynamics and show that surface elevation of Byrd Glacier has been constant for the past ∼40 years.
Highlights
Quantifying how the cryosphere responds to climate forcings is essential for predictions of ice sheet mass loss and sea level rise
These digital elevation models (DEMs) are created without ground control, which means that the geolocation is approximated from the sensor’s rational polynomial coefficients (RPCs), and the subsequent error is entirely dependent on the accuracy of the RPCs [23]
We find that using manually extracted ground control points (GCPs) to apply absolute locations to historical aerial imagery in SfM photogrammetry yields accurate results without requiring in situ, evenly spaced ground control, or other traditional photogrammetric parameters like flight altitude and photo center XY
Summary
Quantifying how the cryosphere responds to climate forcings is essential for predictions of ice sheet mass loss and sea level rise. We build the necessary EXIF files from metadata extracted from the original flight records and use a new method of manually extracting ground control points (GCPs) from high-resolution digital elevation models (DEMs) to provide the missing ground control. This technique has been applied to small Arctic glaciers [11,12], but never to Antarctic glaciers, which are often wider than individual images (where images of just glacier ice have no suitable features for assigning GCPs). To the best of our knowledge, there are no other studies in Antarctica using SfM photogrammetry processing with manually extracted ground control to generate elevations from analog aerial imagery. We demonstrate the validity and accuracy of this elevation processing technique for historical Antarctic data, which can later be applied to this large dataset of historical images
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