Error determination in the photogrammetric assessment of shoreline changes

Abstract

The evaluation of error or uncertainty in shoreline change studies is an issue of prime importance for providing an adequate framework for calculated rates of change, and to allow the establishment of threshold values above which the rates would be significant. In this note a practical, easy-to-use method is presented to estimate error involved in the calculation of shoreline changes on aerial photographs, including the three most used types of shoreline indicators: high water line, dune/cliff toe and cliff top. This approach takes into account the specific characteristics of each shoreline proxy, such as relief in the case of the cliff top or tidal oscillations in the case of the high water line. At the same time it includes the error components that are independent from the proxy, basically related to the technical aspects of the process such as photo scanning and georeferencing. A practical example of application of the method is provided for several types of data inputs, based on shoreline changes around the Bay of Cadiz (SW Spain).

Coastline evolution of Portuguese low-lying sandy coast in the last 50 years: an integrated approach

“…Considering that this study targets low-lying sandy coasts backed by dunes, the coastline indicator used in this study was the foredune toe, and recognized as the morphological feature less affected by short-term (tidal) and medium-term (seasonal) changes (e.g. Komar et al, 2001;Ferreira et al, 2006;Del Río and Gracia, 2013).…”

Morphological and evolutionary classification of sandy beaches in Cadiz coast (SW Spain)

“…Rates of change between the different dates were then calculated on each transect by linear regression technique (Dolan et al, 1991), as it is considered the most statistically robust quantitative method when a limited number of shorelines are available (Crowell et al, 1997). High-accuracy shoreline change data were obtained, and the uncertainty of resulting rates was calculated on a photo-by-photo basis according to the method proposed by Del Río and Gracia (2012), by taking into account spatial resolution of the image, RMS error of the georeferencing process and tiderelated variability in HWL position.…”

Drivers of island beach evolution: insights from an island‐scale study at Boa Vista (Cabo Verde)

“…Shoreline indicator, due to its high dynamic nature, is more affected by short-term (wave, tidal and seasonal) changes (Ferreira et al, 2006;Del Río and Gracia, 2013;Ponte Lira et al, 2016) than the morphology-based coastline indicator. This makes coastline indicator particularly useful in long-term studies (Ponte Lira et al, 2016) as is less influenced by highfrequency changes on the land-water interface.…”