Flood Mapping Google Earth Engine Using Sentinel SAR Satellite Imagery

[@createbyte]

-Get Feature Boundary from:
data.humdata.org/dataset/pakistan-union-council-boundaries-along-with-other-admin-boundaries-dataset
-Functions code:
//declared function to convert the images types and perform the functions
// Function to convert from d
function toNatural(img) {
return ee.Image(10.0).pow(img.select(0).divide(10.0));
}
//Function to convert to dB
function toDB(img) {
return ee.Image(img).log10().multiply(10.0);
}
//Apllying a Refined Lee Speckle filter as coded in the SNAP 3.0 S1TBX:
//github.com/senbox-org/s1tbx/blob/master/s1tbx-op-sar-processing/src/main/java/org/esa/s1tbx/sar/gpf/filtering/SpeckleFilters/RefinedLee.java
//Adapted by Guido Lemoine
// by Guido Lemoine
function RefinedLee(img) {
// img must be in natural units, i.e. not in dB!
// Set up 3x3 kernels
var weights3 = ee.List.repeat(ee.List.repeat(1,3),3);
var kernel3 = ee.Kernel.fixed(3,3, weights3, 1, 1, false);
var mean3 = img.reduceNeighborhood(ee.Reducer.mean(), kernel3);
var variance3 = img.reduceNeighborhood(ee.Reducer.variance(), kernel3);
// Use a sample of the 3x3 windows inside a 7x7 windows to determine gradients and directions
var sample_weights = ee.List([[0,0,0,0,0,0,0], [0,1,0,1,0,1,0],[0,0,0,0,0,0,0], [0,1,0,1,0,1,0], [0,0,0,0,0,0,0], [0,1,0,1,0,1,0],[0,0,0,0,0,0,0]]);
var sample_kernel = ee.Kernel.fixed(7,7, sample_weights, 3,3, false);
// Calculate mean and variance for the sampled windows and store as 9 bands
var sample_mean = mean3.neighborhoodToBands(sample_kernel);
var sample_var = variance3.neighborhoodToBands(sample_kernel);
// Determine the 4 gradients for the sampled windows
var gradients = sample_mean.select(1).subtract(sample_mean.select(7)).abs();
gradients = gradients.addBands(sample_mean.select(6).subtract(sample_mean.select(2)).abs());
gradients = gradients.addBands(sample_mean.select(3).subtract(sample_mean.select(5)).abs());
gradients = gradients.addBands(sample_mean.select(0).subtract(sample_mean.select(8)).abs());
// And find the maximum gradient amongst gradient bands
var max_gradient = gradients.reduce(ee.Reducer.max());
// Create a mask for band pixels that are the maximum gradient
var gradmask = gradients.eq(max_gradient);
// duplicate gradmask bands: each gradient represents 2 directions
gradmask = gradmask.addBands(gradmask);
// Determine the 8 directions
var directions = sample_mean.select(1).subtract(sample_mean.select(4)).gt(sample_mean.select(4).subtract(sample_mean.select(7))).multiply(1);
directions = directions.addBands(sample_mean.select(6).subtract(sample_mean.select(4)).gt(sample_mean.select(4).subtract(sample_mean.select(2))).multiply(2));
directions = directions.addBands(sample_mean.select(3).subtract(sample_mean.select(4)).gt(sample_mean.select(4).subtract(sample_mean.select(5))).multiply(3));
directions = directions.addBands(sample_mean.select(0).subtract(sample_mean.select(4)).gt(sample_mean.select(4).subtract(sample_mean.select(8))).multiply(4));
// The next 4 are the not() of the previous 4
directions = directions.addBands(directions.select(0).not().multiply(5));
directions = directions.addBands(directions.select(1).not().multiply(6));
directions = directions.addBands(directions.select(2).not().multiply(7));
directions = directions.addBands(directions.select(3).not().multiply(8));
// Mask all values that are not 1-8
directions = directions.updateMask(gradmask);
// "collapse" the stack into a singe band image (due to masking, each pixel has just one value (1-8) in it's directional band, and is otherwise masked)
directions = directions.reduce(ee.Reducer.sum());
//var pal = ['ffffff','ff0000','ffff00', '00ff00', '00ffff', '0000ff', 'ff00ff', '000000'];
//Map.addLayer(directions.reduce(ee.Reducer.sum()), {min:1, max:8, palette: pal}, 'Directions', false);
var sample_stats = sample_var.divide(sample_mean.multiply(sample_mean));
// Calculate localNoiseVariance
var sigmaV = sample_stats.toArray().arraySort().arraySlice(0,0,5).arrayReduce(ee.Reducer.mean(), [0]);
// Set up the 7*7 kernels for directional statistics
var rect_weights = ee.List.repeat(ee.List.repeat(0,7),3).cat(ee.List.repeat(ee.List.repeat(1,7),4));
var diag_weights = ee.List([[1,0,0,0,0,0,0], [1,1,0,0,0,0,0], [1,1,1,0,0,0,0],
[1,1,1,1,0,0,0], [1,1,1,1,1,0,0], [1,1,1,1,1,1,0], [1,1,1,1,1,1,1]]);
var rect_kernel = ee.Kernel.fixed(7,7, rect_weights, 3, 3, false);
var diag_kernel = ee.Kernel.fixed(7,7, diag_weights, 3, 3, false);
// Create stacks for mean and variance using the original kernels. Mask with relevant direction.
var dir_mean = img.reduceNeighborhood(ee.Reducer.mean(), rect_kernel).updateMask(directions.eq(1));
var dir_var = img.reduceNeighborhood(ee.Reducer.variance(), rect_kernel).updateMask(directions.eq(1));
dir_mean = dir_mean.addBands(img.reduceNeighborhood(ee.Reducer.mean(), diag_kernel).updateMask(directions.eq(2)));
dir_var = dir_var.addBands(img.reduceNeighborhood(ee.Reducer.variance(), diag_kernel).updateMask(directions.eq(2)));
// and add the bands for rotated kernels
for (var i=1; i

[@PlannerSajad]

Wonderful Sir, this video helped me a lot for my class report on "Impact of Flood and their mitigation strategies in Sindh " thank you Sir for your guidelines..... i really appreciate it....

[@createbyte]

All the best

[@mirwado1384]

​@@createbytesir i have to do research on the topic (pre and post flood water quality analysis in sindh ) so plz sir can u guide me

[@geykum_shakeshigh]

Thank you for the video and the code sir, I appreciate it

[@myatmin6336]

I have a issues which "toDB is not defined" . Please let me know what is this issue?

[@JHN_Productions]

toDB function is not working in my code editor

[@simbarashethondhlana8327]

Well presented. Thank you so much.

[@dhiazahira6846]

Hello sir, thanks for the video. I wanna ask you how to determine the min max value?

[@DorsaMohammadi-zq2nt]

how can access to all codes?

[@jovin.thazhal]

mine showing zero size and boundary is not adding in the layer
what can i do

[@geykum_shakeshigh]

Can I ask a question here mate, am sure you'all have encountered an issue where you have to clip a DEM file for a small area it shows pixels, just pixels, can this be Improved like using GEE to have the exact scale for proper representation of the map?

[@dhiazahira6846]

Sir, what the name of methodh that you use, change detection or something else?

[@facts_tv6343]

Which code can we use to output the final map result. please can you reply below. Thank you

[@createbyte]

map.layer and then include the layer you want add

[@siyadabdirahmansiyad379]

thanks for your kind sharing bro, How can get other countries feature boundaries?

[@createbyte]

Yes . Just search for your country boundary shape files

[@jyotiprakashhati4058]

The code says toDB is not defined.

[@createbyte]

Check the comments section and description
I have pinned the toDB function there
You can simply copy paste that into your editor

[@elsysielatchom]

Good morning Sir thanks for this kind explanation. Please can you share script with us?

[@createbyte]

Will upload soon

[@GISHacks]

Thank you so much. Would you please share the code?

[@eeshacrafts6122]

Good say sir, please i stuck 😢.
My good state size is printing as zero, what do i do?

[@eeshacrafts6122]

Please I would appreciate getting a response as soon as possible

[@createbyte]

Is your issue fixed ?

[@valosspu2024]

i'm getting same value of in inspector of good and flood filter its all same as you

[@birhanukifle517]

It is Nice

[@kingkhan-qb5rj]

Is it possible to calculate total flood area of Pakistan?

[@createbyte]

yes

[@razirajpoot200]

can i get coding?

[@ZeeshanZafarzams706]

But this code shows a lot of water bodies on the eastern side, which we all know is a huge desert. I think its mixing sand with water.

[@SocialAnalyst33]

Asslamualikum Sir. Thanks for This video, Can you share the flood report ! i need it

[@createbyte]

pdma.gos.pk/flood-2022-in-sindh/
Download the pdf from here brother

[@geologistdinesh]

could you send me code of this anaysis

[@createbyte]

Even if I share you the code
It wont run because you wont have the imported assets , which are non shareable at the moment by Earth engine

[@usamakhatab8989]

flood water should be more than simple water. but in this analysis simple water is more. why?

[@dwikifebriyan-z9k]

bang bagi codingnya bang

[@geologistdinesh]

Non-satisfied your answer, we want to see ce script, otherwise no explanation is required

[@createbyte]

Will surely try to work on that in upcoming videos

[@Rajesh-t3l6c]

T