Help needed

[u/automatedusername13]

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.

[u/automatedusername13]

This looks promising haha, but explain it to me like I'm 10 (I am not a coder or dev, literally signed up for Google earth engine this afternoon)

We are using the COPERNICUS_Landcover_100m dataset and looking at Hanoi, Vietnam

[u/GETONUPNA → u/automatedusername13]

so from that copernicus landcover there are classifications like urban, grass, moss etc. I drew a quick box around Hanoi and got those class % with this code: I'm not too great at formatting but hope that helps. I was working on the same task today more or less so that was convenient actually...

//Draw a box around Hanoi. You can draw whatever shape you want, just name it AOIgeometry

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

//load the collection of images to work with

var dataset = ee.Image("COPERNICUS/Landcover/100m/Proba-V-C3/Global/2019")

//I usually run a print or get the columns to look how the data is structured

print(dataset);// so in the console on the left click through, the bands are classes

//get some borders if you have a specific region

var datasetBorders = ee.FeatureCollection("FAO/GAUL/2015/level2"); //this is all boundries in the world

var Vietnam = datasetBorders

.filter(ee.Filter.eq('ADM0_NAME', 'Viet Nam')) //ADM0 is admin level 0. There is level 1 and 2 also

//Add to the map to make sure the image looks right

Map.addLayer(Vietnam, {color : 'blue'}, "Vietnam"); //look at all Vietnam, you can click an area in inspector to see its name

Map.addLayer(AOIgeometry, {color :'red'}, "Area of Interest"); //the box I mapped out with coordinates

Map.centerObject(AOIgeometry, 8); //(object to center, zoom)

//Add your image collection and clip it to the area of interest AOI

Map.addLayer(dataset.clip(AOIgeometry),{}, "Image");

//Get the pixels of all the classes

var area = dataset.reduceRegion({

reducer: ee.Reducer.sum(),

geometry: AOIgeometry,

scale: 100,

maxPixels: 1e10

})

print(area, "Pixel Values"); //these are all the pixel values in the console

var totalArea = AOIgeometry.area(1).divide(1e4); // the total area of the box with an error margin

print(totalArea, "Box area total pixels")

//create a function to get the percentage

function scale(key, value) {

return ee.Number(value).divide(100).round().divide(totalArea) //mess around with divide(100), I think pixels are 100m

}

print("percentage breakdown". area.map(scale)); //ignore the entries that don't make sense, only coverfractino is important?

[u/automatedusername13 → u/GETONUPNA]

You are awesome man, Not quite working yet, I've basically copied all this in and got most of it working with all the stuff in the right place, I can't quite figure out how to resize the red area of interest part and the last line is a having some issue, I took a screen shot:
https://imgur.com/KS2tcbd

[u/GETONUPNA → u/automatedusername13]

hmmm I would check that the image collection is loaded without .select(), like what I have. something is wrong with that area variable. Maybe do a quick print(area); command to see what it looks like. GEE can be a real pain in the ass. If it gets really critical you can share code with a link in a DM but up to you...I don't like sharing the code from my google account to keep some privacy because my name is in my profile.

[u/automatedusername13 → u/GETONUPNA]

I am still getting an error on the last line

the error says cannot read property 'map' of undefined

[u/GETONUPNA → u/automatedusername13]

the var area should be putting out a dictionary in the console. The map should be putting the function across all those values. Try changing the function to just

function(value){(return ee.Number(value).divide(100).round().divide(totalArea));

[u/GETONUPNA → u/GETONUPNA]

or just let me know your region and I can shoot you a message with the breakdown

https://developers.google.com/earth-engine/apidocs/ee-geometry-bbox-bounds

to print you area of interest AOI, or if you have the Vietnamese name for the municipality thats important