Temporal analysis - burned area

Thanks, your help is much appreciated! I got the results I wanted with the script below:

    function setup (dss) {
      // get all bands for display and analysis
      setInputComponents([dss.B02,dss.B03,dss.B04,dss.B08,dss.B12]);
      // return as RGB
      setOutputComponentCount(3);
    }

    function filterScenes (scenes, inputMetadata) {  
      return scenes.filter(function (scene) {
        // set dates for pre-and-post fire analysis
        var allowedDates = ["2017-05-15","2017-06-24"]; // Knysna fires
        // format scene date timestamp to match allowed dates 
        var sceneDateStr = dateformat(scene.date);
        if (allowedDates.indexOf(sceneDateStr)!= -1) return true;
        else return false;
      });
    }

    // Normalized Burn Ration calculation
    function calcNBR(sample) {
      var denom = sample.B08+sample.B12;
      var nbrval = ((denom!=0) ? (sample.B08-sample.B12) / denom : 0.0);
      return nbrval;
    }

    function dateformat(d){  
      var dd = d.getDate();
      var mm = d.getMonth()+1;
      var yyyy = d.getFullYear();
      if(dd<10){dd='0'+dd}
      if(mm<10){mm='0'+mm}
      var isodate = yyyy+'-'+mm+'-'+dd;
      return isodate;
    }

    function evaluatePixel(samples,scenes) {  
      var nbrpre = 0;
      var nbrpost = 0;  

      // get pre-fire image
      nbrpre = calcNBR(samples[1]);
      // get post-fire image
      nbrpost = calcNBR(samples[0]);          
      // get difference 
      var dnbr = nbrpre - nbrpost;
      // set output display layers
      var NaturalColors = [3 * samples[0].B04, 3 * samples[0].B03, 3 * samples[0].B02];          
      var burnModerate = [1,0.5,0];
      var burnSevere = [1,0,0];
      return (dnbr < 0.27 ?
              NaturalColors : (dnbr < 0.66 ?
                burnModerate : burnSevere)
      );

    }

In case you want to compare two specific dates, you might use something along the lines of:

function filterScenes (scenes, inputMetadata) {
    return scenes.filter(function (scene) {
	  var allowedDates = ["2017-11-05","2017-12-05"];
      
      var sceneDateStr = getDateInISO(scene.date);
      if (allowedDates.indexOf(sceneDateStr)>=0) return true;
      else return false;
    });
}

in the filterScenes section.
To do this in a dynamic fashion, you would want to use EVALSCRIPT parameter - e.g. prepare the script in your application, then encode it (BASE64) and then pass it as EVALSCRIPT.

Try this script:

function    setup (dss) {
  setInputComponents([dss.B08,dss.B12]);
  setOutputComponentCount(1);
}
 
function filterScenes (scenes, inputMetadata) {
  return scenes.filter(function (scene) {
       return scene.date.getTime()>=(inputMetadata.to.getTime()-2*31*24*3600*1000) ;
    });
}
 
function calcNBR(sample) {
  var denom = sample.B08+sample.B12;
  return ((denom!=0) ? (sample.B08-sample.B12) / denom : 0.0);
}
 
function evaluatePixel(samples,scenes) { 
  var nbrpre = 0;
  var nbrpost = 0;
  
  var endMonth = scenes[0].date.getMonth();
  var startMonth = scenes[scenes.length-1].date.getMonth();
 
  for (var i=0;i<samples.length;i++) {
   
    if (scenes[i].date.getMonth()==endMonth){
      nbrpost = calcNBR(samples[i]);
    }
    if (scenes[i].date.getMonth()==startMonth){
      nbrpre = calcNBR(samples[i]);
    }
  }
  var dnbr = nbrpre - nbrpost;
 return [dnbr];
}

A little tweaked for nicer visuals:

function setup (dss) {
  // get all bands for display and analysis
  setInputComponents([dss.B02,dss.B03,dss.B04,dss.B05,dss.B08,dss.B12]);
  // return as RGB
  setOutputComponentCount(3);
}

function stretch(val, min, max) {return (val - min) / (max - min);}

function filterScenes (scenes, inputMetadata) {  
return scenes.filter(function (scene) {
// set dates for pre-and-post fire analysis
var allowedDates = ["2017-05-15","2017-06-24"]; // Knysna fires
// format scene date timestamp to match allowed dates 
var sceneDateStr = dateformat(scene.date);
if (allowedDates.indexOf(sceneDateStr)!= -1) return true;
else return false;
  });
}

// Normalized Burn Ration calculation
function calcNBR(sample) {
  var denom = sample.B08+sample.B12;
  var nbrval = ((denom!=0) ? (sample.B08-sample.B12) / denom : 0.0);
  return nbrval;
}

function dateformat(d){  
  var dd = d.getDate();
  var mm = d.getMonth()+1;
  var yyyy = d.getFullYear();
  if(dd<10){dd='0'+dd}
  if(mm<10){mm='0'+mm}
  var isodate = yyyy+'-'+mm+'-'+dd;
  return isodate;
}

function evaluatePixel(samples,scenes) {  
  var nbrpre = 0;
  var nbrpost = 0;  
  
  // get pre-fire image
  nbrpre = calcNBR(samples[1]);
  // get post-fire image
  nbrpost = calcNBR(samples[0]);  
  // get difference 
  var dnbr = nbrpre - nbrpost;
  // set output display layers
  var stretchMin = 0.05;
  var stretchMax = 1.00;
  var NaturalColors = [stretch(2.8 * samples[0].B04 + 0.1 * samples[0].B05, stretchMin, stretchMax), stretch(2.8 * samples[0].B03 + 0.15 * samples[0].B08, stretchMin, stretchMax), stretch(2.8 * samples[0].B02, stretchMin, stretchMax)];  
  var burnModerate = [stretch(2.8 * samples[0].B04 + 0.1 * samples[0].B05, stretchMin, stretchMax)+0.5, stretch(2.8 * samples[0].B03 + 0.15 * samples[0].B08, stretchMin, stretchMax)+0.5, stretch(2.8 * samples[0].B02, stretchMin, stretchMax)];  
  var burnSevere = [stretch(2.8 * samples[0].B04 + 0.1 * samples[0].B05, stretchMin, stretchMax)+0.5, stretch(2.8 * samples[0].B03 + 0.15 * samples[0].B08, stretchMin, stretchMax), stretch(2.8 * samples[0].B02, stretchMin, stretchMax)];
  return (dnbr < 0.27 ?
  NaturalColors : (dnbr < 0.66 ?
  burnModerate : burnSevere)
  );
  
}

Link

That looks great. Thanks for sharing it.

An example here (make sure to switch on Temporal processing in Effects pane)

Sentinel Playground

Sentinel Playground application for playing with Sentinel satellite imagery

I have committed the script to Custom script github repository.

Thanks to both.

Very nice! Thanks.

Hi ! I found very interesting what you are doing.
I tried to run the scrypt on the playground with out success. I zoomed in a area where i know a fire scar, and changed the pre and post fire dates. Should i change any other parameter?

Thanks in advance

So many thanks! Nice job!

It could be very interesting to export the results into a vectorized polygon, do you think is possible in this environment?

Cheers

Fires in Córdoba, Argentina

Hi,

you need to use the “temporal” playground app, which is in prototype mode, e.g.:

Sentinel Playground

Sentinel Playground

Sentinel Playground application for playing with Sentinel satellite imagery

And then do as you suggested.
If it does not work, let me know, which area you are looking at and which are the dates, so that we can debug.

Best

Hi,

Great script and idea, up until I came across this I had been downloading terabytes of sentinel 2 to calculate difference NBR. However, I cannot see to get the above script to work in the Sentinel Hub Playground (“Error loading image:”), I am a complete noob to this platform. Do you mind please pointing me in the right direction?

Thanks in advance.

Kind regards

Looks nice, thanks for sharing.
Vectorized polygon is an output option, see:
https://sentinel-hub.com/develop/documentation/api/output-formats
You would need to configure your Sentinel Hub account properly and then call the service via API though.

Thank you for the script and for the tweaked version, it works great!

I tried to run the script also in Sentinel EO Browser but it didn’t work. I guess it does work only in the Playground Temporal web app?

Hi

Thank you very much for the very interesting script. It is great.

I’m probably asking something very simple, but my problem is that I’m not a programmer. I don´t know if it is possible to use a script like this in “wms configurator”.

In my case what I need is an image resulting from subtracting NDVI values between two dates. But trying to make you more simple, if you can tell me how to use the “Burned area temporal analysis” script in “wms configurator” it would be great. Then I will try to adapt it to what I need.

It is not urgent and thank you very much for you time

Hi,
did you use “Temporal version of Sentinel Playground” as linked here:

Hi Nicolas, you need to use the “temporal” playground app, which is in prototype mode, e.g.: And then do as you suggested. If it does not work, let me know, which area you are looking at and which are the dates, so that we can debug. Best, Grega

Or try one link directly as described here:
Temporal analysis - burned area?

Hello

Thank you very much for the reply. It’s great if this option is implemented in the future. Anyway, EO Browser is still very useful and the statistical info option is already very interesting for temporary analysis.

Greetings.

You are right, multi-temporal processing is not yet supported in EO Browser, which was designed to show data from single time slices. We do plan to update this, but not one of the top priority features.
You can obviously take EO Browser application source-code and deploy your own, modified, version:

GitHub - sentinel-hub/EOBrowser: The Earth Observation Browser is a search...

The Earth Observation Browser is a search tool for Sentinel-1, -2, -3, Landsat 5, 7, 8, Modis and Envisat satellite imagery - GitHub - sentinel-hub/EOBrowser: The Earth Observation Browser is a sea...

You can use OGC API to do so:
https://www.sentinel-hub.com/develop/documentation/api/ogc_api

It is possible to understand how to export the analysis performed as a script.
grazie

Hi,Thank you for the script. I tried running it for my area but it returned a black image. @pierre.markuse ,@fcbasson and @gmilcinski could you please give me ideas on how to customize it to fit my area. What parameters do I need to change/add on the script?

Please note I have no programming skills, I am still trying to teach myself programming.

Sorry for the question, but I can’t make this step to download the data.
could you help me if you know a tutorial.
I should do a task but I don’t know the construction of the API very well.
Thanks for your help

Im trying to get this working in EO Hub as WMS service, can anyone help what programing tweaks are required?

Hi, ive noticed to get it working you must do a few things in playground.

1. Zoom in to your area of interest (hint this is only likely to work if your in one Row/Path ie square of satelite imagery, but they are large should you are mostly right
2. Click on the date selector in playground find before and after dates for which images were taken that day (you can tell by the light grey circle that pops up.
3. Select the after date from this menu
4. Also change the dates in the script to those dates
5. Note the current image displayed (controlled by the date selector in playground can be anytime after but not before or during the dates inputed into the script

Hi,

I checked the custom script in your WMS collection and realised that you are using an outdated evalscript. Read all about the transition to Evalscript V3 in the documentation and the corresponding forum posts.

Now, to solve your problem you need to take care of two things:

1. You should use this updated and fixed V3 script for burned area visualisation.
2. Make sure that there is data available in your area of interest for the dates you specify in line 26 of the updated script. Looking at your collection that line would read var allowedDates = ["2019-08-22","2019-09-11"]; in your case.

This worked for me when I tested it in QGIS with the dates and AOI from the custom script example. For other interesting custom scripts for fire detection, wildfire visualisation or burn scar detection please check out our custom scripts repository, which you can also contribute to and share your scripts with other users.

I hope that helps!

Cheers

Thank you so much for your response, I was able to fit the script to my area and show the fire.

I have been trying to take it to ArcGIS online using WMS service by copying and pasting the script on custom script editor on my WMS templates but it doesn’t work. Please assist on how to get this working