![](\"../Supplementary_data/dea_logo.jpg\"){kind=logo}
\n",
"\n",
"* **[Sign up to the DEA Sandbox](https://app.sandbox.dea.ga.gov.au/)** to run this notebook interactively from a browser\n",
"* **Compatibility:** Notebook currently compatible with the `DEA Sandbox` environment only\n",
"* **Products used:** \n",
"[ga_ls5t_ard_3](https://explorer.dea.ga.gov.au/ga_ls5t_ard_3),\n",
"[ga_ls7e_ard_3](https://explorer.dea.ga.gov.au/ga_ls7e_ard_3),\n",
"[ga_ls8c_ard_3](https://explorer.dea.ga.gov.au/ga_ls8c_ard_3)\n",
"* **Prerequisites:** For more information about the tidal modelling step of this analysis, refer to the [Tidal modelling notebook](../How_to_guides/Tidal_modelling.ipynb)"
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"## Background\n",
"Intertidal environments support important ecological habitats (e.g. sandy beaches and shores, tidal flats and rocky shores and reefs), and provide many valuable benefits such as storm surge protection, carbon storage and natural resources for recreational and commercial use. \n",
"However, intertidal zones are faced with increasing threats from coastal erosion, land reclamation (e.g. port construction), and sea level rise. \n",
"Accurate elevation data describing the height and shape of the coastline is needed to help predict when and where these threats will have the greatest impact. \n",
"However, this data is expensive and challenging to map across the entire intertidal zone of a continent the size of Australia.\n",
"\n",
"### Digital Earth Australia use case\n",
"The rise and fall of the tide can be used to reveal the three-dimensional shape of the coastline by mapping the boundary betweeen water and land across a range of known tides (e.g. from low tide to high tide). \n",
"Assuming that the land-water boundary is a line of constant height relative to mean sea level (MSL), elevations can be modelled for the area of coastline located between the lowest and highest observed tide. \n",
"\n",
"Imagery from satellites such as the NASA/USGS Landsat program is available for free for the entire planet, making satellite imagery a powerful and cost-effective tool for modelling the 3D shape and structure of the intertidal zone at regional or national scale. \n",
"Recently, Geoscience Australia combined 30 years of Landsat data from the Digital Earth Australia archive with tidal modelling to produce the first 3D model of Australia's entire coastline: the **DEA Intertidal Elevation** dataset (also known as NIDEM; for more information, see [Bishop-Taylor et al. 2019](https://doi.org/10.1016/j.ecss.2019.03.006) or [access the dataset here](http://pid.geoscience.gov.au/dataset/ga/123678)). \n",
"\n",
"## Description\n",
"\n",
"In this example, we demonstrate a simplified version of the NIDEM method that combines data from the Landsat 5, 7 and 8 satellites with tidal modelling, image compositing and spatial interpolation techniques. \n",
"We first map the boundary between land and water from low to high tide, and use this information to generate smooth, continuous 3D elevation maps of the intertidal zone. \n",
"The resulting data may assist in mapping the habitats of threatened coastal species, identifying areas of coastal erosion, planning for extreme events such as storm surges and flooding, and improving models of how sea level rise will affect the Australian coastline. \n",
"This worked example takes users through the code required to:\n",
"\n",
"1. Load in a cloud-free Landsat time series\n",
"2. Compute a water index (NDWI)\n",
"3. Tag and sort satellite images by tide height\n",
"4. Create \"summary\" or composite images that show the distribution of land and water at discrete intervals of the tidal range (e.g. at low tide, high tide)\n",
"5. Extract and visualise the topography of the intertidal zone as depth contours\n",
"6. Interpolate depth contours into a smooth, continuous Digital Elevation Model (DEM) of the intertidal zone\n",
"\n",
"***\n"
]
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"## Getting started\n",
"**To run this analysis**, run all the cells in the notebook, starting with the \"Load packages\" cell.\n",
"\n",
"**After finishing the analysis**, return to the \"Analysis parameters\" cell, modify some values (e.g. choose a different location or time period to analyse) and re-run the analysis.\n",
"There are additional instructions on modifying the notebook at the end."
]
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"source": [
"### Load packages\n",
"Load key Python packages and supporting functions for the analysis."
]
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"metadata": {},
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"/env/lib/python3.8/site-packages/distributed/node.py:180: UserWarning: Port 8787 is already in use.\n",
"Perhaps you already have a cluster running?\n",
"Hosting the HTTP server on port 45189 instead\n",
" warnings.warn(\n"
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