Regarding Time Series analysis in earth engine

Question

I have been working on time series change using Landsat 5,7 and 8 satellite images. The objective of my study is to see any changes in features like forest, agriculture etc over time using NDVI To observe and visualize the changes, firstly I need a combine chart of monthly NDVI of all above landsat series.

Secondly, I have made mean images of ndvi for each year (a mean of all of the months). I wish to make a chart of mean annual ndvi values vs years, for all the features.

Answer 1

I think this question is pretty broad, but there are sufficient examples inside the Google Earth Engine to get you started. If you will have a specific question later on you can ask it with the piece of code you have been trying so far.

See this example to calculate normalized differences (for example NDVI and NDWI):

https://code.earthengine.google.com/8e062e11bb632c20ce320c5f7f10dc41

Then follow this example script by Google to make a time-series analysis:

https://code.earthengine.google.com/7bfc69498939433590a040e11fd949b1

You can find manny other examples under script -> Examples in the code editor.

Answer 2

// for graph/chart that contain mean NDVI of every year

     var plotNDVI = ui.Chart.image.seriesByRegion(addnullimages, studyarea,ee.Reducer.mean(),
'nd',500,'system:index')
              .setChartType('LineChart').setOptions({
                title: 'NDVI short-term time series',
                hAxis: {title: 'Date'},
                vAxis: {title: 'NDVI'}
});


  print(plotNDVI);

Answer 3

you can use this code....

// for graph/chart that contain mean NDVI of every year

  var plotNDVI = ui.Chart.image.seriesByRegion(addnullimages, studyarea,ee.Reducer.mean(),
'nd',500,'system:index')
              .setChartType('LineChart').setOptions({
                title: 'NDVI short-term time series',
                hAxis: {title: 'Date'},
                vAxis: {title: 'NDVI'}
});


  print(plotNDVI);