Charlton, M.

Coveney, S.

Fotheringham, S

Sweeney, J.

English

Enlighten: Publications

  
 
 
 
 
 
 
 
Coveney, S., Fotheringham , S, Charlton, M., and Sweeney, J. (2007) GPS 
verification of National Mapping Agency topographical data for generation 
of high-accuracy GPS-derived topographic model data for sea-level rise 
prediction in protected salt marsh areas.In: EUGeo 2007, 20-23 Aug 2007, 
University of Amsterdam, The Netherlands. 
 
Copyright © 2007 The Authors 
 
 
 
 
http://eprints.gla.ac.uk/87716/ 
 
 
 
 
Deposited on: 15 November 2013 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Enlighten – Research publications by members of the University of Glasgow 
http://eprints.gla.ac.uk 
GPS verification of National Mapping Agency topographical data for generation 
of high-accuracy GPS-derived topographic model data for sea-level rise 
prediction in protected salt marsh areas. 
Seamus Coveney1, Stewart Fotheringham2, Martin Charlton3, John Sweeney4 
1National Centre for Geocomputation NUIM, Ireland & Department of Geography, NUIM, Ireland. 
Telephone: (00353-1-7086196)  
Fax: (00353-1-7086456)  
Email: seamus.j.coveney@nuim.ie 
2 & 3 National Centre for Geocomputation NUIM, Ireland. 
4 Department of Geography, NUIM, Ireland. 
Global average temperatures have increased by approximately 0.6°C during the 20th 
century, and are projected to increase by a minimum additional 1.4 °C by 2100. The 
relationship between atmospheric warming and sea-level rise (SLR) is well 
documented, and is expected to lead to SLR of up to 0.8m by 2100 (IPCC, 2007). 
Estuaries are predominantly sedimentary environments, and are characterised by 
shallow sloping gradients, making them particularly sensitive to SLR. The Shannon 
estuary is the largest river estuary in Ireland and is designated as a Special Area of 
Conservation, providing legislative protection for a range of habitat types, including 
estuarine salt marsh (E.U., 1992). 
This paper discusses the development of methods for enhancing the accuracy of SLR 
predictions in the estuary up to 2100, with a particular focus on generating accurate 
predictions for salt marsh areas. Historical tidal records are frequently used to assess 
generalised regional sea-level trends (Woodworth et al., 1999). SLR is caused by 
eustatic change (rising water level) and isostatic change (land surface crustal 
movements). Ireland is experiencing both eustatic and isostatic changes. The major 
force for eustatic change is climate change, while the source of isostatic change is 
post-glacial crustal rebound. Post-glacial rebound in the north of Ireland is leading to 
compensatory downward crustal movements further south, providing an additional 
input to SLR in the south of Ireland. The specific proportional contributions of 
eustatic and isostatic forces are not as important as their combined impact on SLR 
trends. Twice-daily high-tide data from Limerick dock (15km from the project study 
area) suggests SLR of 4.0 - 4.5mm/yr for the period from 1877 - 2004. This trend is 
approximately 2.5 times greater than the observed global average SLR trend since the 
Industrial Revolution. This suggests that SLR in the Shannon estuary over the next 
century may be significantly larger than global predictions from the IPCC. 
The generation of meaningful SLR predictions presupposes the existence of accurate 
topographical data. National mapping agency Digital Elevation Model (DEM) data for 
Ireland is characterised by vertical errors of ±3m, suggesting that it is unsuitable for 
use in SLR modelling. High-accuracy Aerial Laser Scanning (LIDAR) data is 
generally preferred for SLR modelling, but LIDAR surveys for Ireland have not yet 
extended to include most of the western seaboard (including the Shannon estuary). 
While the quality of the OSi DEM suggests that it is not suitable for direct SLR 
modelling, it may be the case that errors in this dataset are lower at the coast. DEM 
are often related to topographic complexity, suggesting that flat coastal areas may be 
subject to DEM errors (Holmes et al., 2000). 
RTK and post-processed survey grade GPS, plus Terrestrial Laser scanning (TLS) 
surveys were carried out across a number of adjacent salt marsh areas in the estuary to 
evaluate error ranges in the National DEM dataset, and to provide the basis for a new 
high-quality local DEM for SLR modelling in the Shannon estuary study area. Errors 
in the OSi DEM were found to be within published ranges, with the largest errors 
occurring towards the coastline (i.e. the theoretical zero contour). This confirmed the 
unsuitability of the OSi data for use as the basis of indicative SLR modelling. The 
accuracy of the GPS survey data was validated against external GPS reference 
stations, confirming the average accuracy of the 600-point GPS survey dataset to 
between 1 and 2cm. vertical errors within in the TLS data were within the 1 – 2cm 
range also, suggesting that the GPS and TLS datasets could indeed be used to generate 
a local DEM of quality sufficient for meaningful SLR prediction. 
The survey-derived DEM data is now being used to accurately define SLR risk in the 
study area, and the DEM data is being used in conjunction with local erosion and 
deposition data and coastal morphology models to predict specific risks within 
protected salt marsh within the study area. 
 
References 
E.U., (1992), Council Directive 92/43/EEC; on the conservation of natural habitats 
and of wild fauna and flora. Office for Official Publications of the European 
Communities. 
Holmes K.W., Chadwick O.A. & Kyriakidis P.C. (2000), Error in a USGS 30-meter 
digital elevation model and its impact on terrain modelling. Journal of Hydrology, 
233, pp. 154-173. 
I.P.C.C., (2001), Climate change 2001: Impacts, Adaptation and Vulnerability. in 
McCarthy. J., Canziani, O.F., Leary, N.A., Dokken, D.J. and White, K.S. (eds.), 
Contribution of Working Group II to the Third Assessment Report of the 
Intergovernmental Panel on Climate change. Cambridge University Press. 
Woodworth, P.L., Tsimplis, M.N., Flather R.A. and Shennan, I. (1999), A review of 
the trends observed in British Isles mean sea level data measured by tide gauges. 
Geophysical Journal International, 136, 3, p.651-670. 


GPS verification of National Mapping Agency topographical data for generation of high-accuracy GPS-derived topographic model data for sea-level rise prediction in protected salt marsh areas

http://eprints.gla.ac.uk/87716/1/87716.pdf

GPS verification of National Mapping Agency topographical data for generation of high-accuracy GPS-derived topographic model data for sea-level rise prediction in protected salt marsh areas

Abstract

Similar works

Full text

Available Versions

Enlighten: Publications