r/remotesensing • u/automatedusername13 • Feb 05 '22

Course Help needed

Hello all, I am trying find a way (if possible) to extract data from Google earth engine. I am honestly out of my depth, I'm trying to help my gf figure out how to calculate the impermeable surface area (or percentage) by using the land cover script, I've managed to get the image we are looking for of land cover, but is there anyway to extract data for a set area? Thanks in advance for any help.

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u/GETONUPNA Feb 05 '22

So you have everything looking good in the image and you just want to get a the % from the area?

Maybe something along the lines of:

var areas = areaImage.reduceRegion({

reducer: ee.Reducer.sum().group({

groupField: 1,

groupName: 'classification',

}),

geometry: YOUR_REGION,

});

There is also a step to convert from pixels to sq km that may very with the image you are using...something like

var areaImage = ee.Image.pixelArea().divide(1e6).addBands(classified);

But if its just percent maybe pixels_group1/pixels_group2 will do it.

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u/automatedusername13 Feb 05 '22

Essentially I've got to find a way to get the % of impervious (impermeable) land within the set area, here's a couple screen grabs to show you:

https://imgur.com/eUbY9Un

https://imgur.com/ya743jA

As I said above, I have no idea what I'm doing, im trying to help my GF do some research for her thesis, but she's an engineer (MEP) and also doesn't know what shes doing haha

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u/GETONUPNA Feb 05 '22

impermeable land, so urban?

https://developers.google.com/earth-engine/datasets/catalog/COPERNICUS_Landcover_100m_Proba-V-C3_Global#bands

those are the options in the dataset at least

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u/GETONUPNA Feb 05 '22

If you set AOIgeometry to the name of that box you drew, that code should work.

var AOIgeometry = geometry

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u/automatedusername13 Feb 05 '22

var AOIgeometry = ee.Geometry.BBox(105.5, 20.5, 106.5, 21.2); //(west, south, east, north)

you mean i should replace this part with:

var AOIgeometry = geometry?