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Sea level rise and Google Earth / Maps

A great day with Priory School yesterday, examining the issue of sea level rise  in the Portsmouth area. We trialled a number of hands-on sessions, which were great fun and will write about these when we have media releases completed to use the photos of students working on the beach.

For now, here are some ideas that were jogged by looking at how ipads might be used to inform a walking tour of a coastal area.

The image below is of a map overlay created in Google Earth, showing the flood cells and sub-cells delineated by the council. Image overlays are fairly easy to create.

The Google Earth file was then saved and uploaded online. Pasting the url of the online file into the search box of Google Maps, allows you to see it as above. Note that you can use Google Maps in Earth mode so that 3D buildings show up and you can tilt the map.

We also created some polygons in Google Earth, again an easy thing to do. The different polygons were given colours and made opaque so that you could see the layers and the underlying imagery. You can see the key to the left below as well.

The ordnance datum in Google Earth and the altitude of the different layers is not quite nuanced enough to show localised flooding predictions on a 25, 50, 100 year timeline and looking to finesse these techniques before sharing more fully, but hope you get the idea.

2 Responses to “Sea level rise and Google Earth / Maps”

  1. anon says:

    This technique doesn’t work properly for polygons that are too big, the curve of the earth gets in the way. The polygons are flat, the earth is (oblate) sphere, meaning a polygon with corners at 0m will have the centre lower than a point on the land is above sea-level.

    Draw a big polygon on the ocean, only some is visible. Leaning over the view in Google Earth can also show the issue.

    Is there not a way to just put a ~sphere on the whole globe at sea-level, plus or minus what the user wants?

  2. Digital Explorer says:

    You are absolutely correct. The method only works for local and small areas such as the example shown. There is no way of putting a sphere over the whole globe. In fact the surface imagery is a series of tiles.

    If you have some time on your hands, looking at the global picture would require someone creating a series of tessellated polygons. And then there is the issue that sea level rise is not uniform across the world.

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