Tidal variations might affect the results. So, how can I consider tidal variation in a scientific way?
Various methods have been created to extract shoreline from satellite images. Since the reflection of water in IR bands are almost Zero and most of vegetation have a bigger reflection versus water, shoreline can be extracted from even one band of the image. (e.g. this extraction can be achieved from Thresholding on one IR band of TM and ETM+ images.)
Hello Faisal, I would recommend SAR imagery if it is a large, open, and remote area. The position of the shoreline is really clear with a simple bit of code looking for grey-scale changes (see Mehdi's answer), and, if you have some DEM information, the height of the shoreline can thus be calculated; see this paper: DOI: 10.1016/j.ecss.2013.02.009 (Understanding the variability of an extreme storm tide along a coastline, which you can download from my publications)
Hello Faisal, I would recommend SAR imagery if it is a large, open, and remote area. The position of the shoreline is really clear with a simple bit of code looking for grey-scale changes (see Mehdi's answer), and, if you have some DEM information, the height of the shoreline can thus be calculated; see this paper: DOI: 10.1016/j.ecss.2013.02.009 (Understanding the variability of an extreme storm tide along a coastline, which you can download from my publications)
You can find a lot of stuff in this book, where shoreline extraction from satellite images has been discussed:
http://www.beachmed.it/Portals/0/SOUSPROJETS/2_1%20OPTIMAL/BeachErosion%20lowres.pdf
With a webcam, we extracted the shoreline from 3 images a day during 5 following days of sea calm and averraging them. In this way we had montly position of the shoreline (paper available).
For me shoreline is the zero ibobath, no trash line, vegetation line, dune foot, etc. Not different from the e.g. 100 m contour in a mountain. For us water doesn't exist when surveying!
I'm interested in collaborating on this topic, if you like.
Cheers,
Enzo
We have used the border between the non-vegetated beach and vegetated dunes in sandy coastal areas to position the shoreline. This border is identifiable in satellite images and aerial photographs. By not being affected by the daily tidal variations of the waterline, it provides a reasonable indication of the medium to long-term maximum run-up. Apparently, that is a valuable indicator for erosion and overwash risk assessments.
The problem is that in many beachs the transition is beach - buildings.
The shoreline is the zero m above the datum; any other definitions are shortcuts in face of the problem.
Dear Enzo
the link is not working http://www.beachmed.it/Portals/0/SOUSPROJETS/2_1%20OPTIMAL/BeachErosion%20lowres.pdf
To clarify the situation, I do have tww worldview satellite images with a spatial resolution less than 1 m. One of them was captured on 2007 and the other one on 2013. the 2007 was captured during the high-tide time and the 2013 was captured during the low-tide. For sure, if I did not adjust the tidal variation, my result would be inaccurate.
I entered just now. Try this.
https://www.researchgate.net/publication/262098857_Beach_Erosion_Monitoring_-_Results_from_BEACHMED-eOpTIMAL_Project
If problems send me your address and I'll send you a copy of the book.
Cheers
Enzoi
Book Beach Erosion Monitoring - Results from BEACHMED-e/OpTIMAL Project
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