GEE: Creating Multiple ImageCollections Based On Date Property

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Introduction

Google Earth Engine (GEE) is a powerful platform for geospatial analysis and visualization. One of its key features is the ability to work with large collections of images, which can be filtered and processed using various methods. In this article, we will explore how to create multiple ImageCollections based on the date property of the images.

Understanding ImageCollections

An ImageCollection in GEE is a collection of images that can be filtered and processed using various methods. ImageCollections can be created from a variety of sources, including Landsat, Sentinel-2, and MODIS. Each image in the collection has a set of properties, including the date of acquisition, which can be used to filter the collection.

Filtering ImageCollections by Date

Filtering an ImageCollection by date is a common operation in GEE. This can be done using the system:index property, which contains the date of acquisition of each image. To filter an ImageCollection by date, you can use the filter method, which takes a function as an argument. This function should return a boolean value indicating whether the image should be included in the filtered collection.

Example: Filtering an ImageCollection by Date

// Create an ImageCollection
var collection = ee.ImageCollection('LANDSAT/LC08/C01/T1')

// Filter the collection by date
var filteredCollection = collection.filterDate('2015-01-01', '2016-01-01')

In this example, we create an ImageCollection from the Landsat 8 dataset and filter it to include only images acquired between January 1, 2015, and January 1, 2016.

Creating Multiple ImageCollections by Date

In some cases, you may want to create multiple ImageCollections based on the date property of the images. This can be done using the map method, which applies a function to each element of the collection.

Example: Creating Multiple ImageCollections by Date

// Create an ImageCollection
var collection = ee.ImageCollection('LANDSAT/LC08/C01/T1')

// Create multiple ImageCollections by date
var collections = collection.map(function(image) 
var date = ee.Date(image.get('systemindex'))
if (date.get('year') === 2015) {
return ee.ImageCollection(image).filterDate('2015-01-01', '2015-12-31')
 else if (date.get('year') === 2016) {
return ee.ImageCollection(image).filterDate('2016-01-01', '2016-12-31')
} else {
return ee.ImageCollection(image)
}
})

In this example, we create an ImageCollection from the Landsat 8 dataset and use the map method to create multiple ImageCollections based on the date property of the images. Each ImageCollection includes only images acquired in a specific year.

Using the MGRS_TILE Property

In addition to filtering by date, you can also use the MGRS_TILE property to select specific images from an ImageCollection. The MGRS_TILE property contains the Grid Reference System (MGRS) tile identifier of each image.

Example: Filtering an ImageCollection by MGRS_TILE

// Create an ImageCollection
var collection = ee.ImageCollection('LANDSAT/LC08/C01/T1')

// Filter the collection by MGRS_TILE
var filteredCollection = collection.filter(ee.Filter.eq('MGRS_TILE', '30SNE'))

In this example, we create an ImageCollection from the Landsat 8 dataset and filter it to include only images with the MGRS_TILE identifier '30SNE'.

Conclusion

In this article, we explored how to create multiple ImageCollections based on the date property of the images in GEE. We also discussed how to filter an ImageCollection by date and MGRS_TILE. By using these methods, you can create customized ImageCollections that meet your specific needs.

Future Work

In the future, we plan to explore more advanced methods for filtering and processing ImageCollections in GEE. This may include using machine learning algorithms to classify images and create new ImageCollections based on the results.

References

  • Google Earth Engine Documentation: ImageCollection
  • Google Earth Engine Documentation: Filter
  • Google Earth Engine Documentation: Map

Code

The code used in this article is available on the GEE Code Editor. You can access the code by clicking on the following link: GEE Code Editor

Note

Introduction

In our previous article, we explored how to create multiple ImageCollections based on the date property of the images in Google Earth Engine (GEE). We also discussed how to filter an ImageCollection by date and MGRS_TILE. In this article, we will answer some frequently asked questions (FAQs) related to creating multiple ImageCollections based on date property in GEE.

Q: What is the difference between system:index and system:time_start properties?

A: The system:index property contains the date of acquisition of each image, while the system:time_start property contains the start time of the image acquisition. The system:index property is a string in the format "YYYY-MM-DDTHH:MM:SS", while the system:time_start property is a Date object.

Q: How can I filter an ImageCollection by date range?

A: You can use the filterDate method to filter an ImageCollection by date range. The method takes two arguments: the start date and the end date. For example:

var collection = ee.ImageCollection('LANDSAT/LC08/C01/T1')
  .filterDate('2015-01-01', '2016-01-01')

Q: How can I create multiple ImageCollections based on date property?

A: You can use the map method to create multiple ImageCollections based on date property. The method applies a function to each element of the collection. For example:

var collection = ee.ImageCollection('LANDSAT/LC08/C01/T1')
  .map(function(image) {
    var date = ee.Date(image.get('system:index'))
    if (date.get('year') === 2015) {
      return ee.ImageCollection(image).filterDate('2015-01-01', '2015-12-31')
    } else if (date.get('year') === 2016) {
      return ee.ImageCollection(image).filterDate('2016-01-01', '2016-12-31')
    } else {
      return ee.ImageCollection(image)
    }
  })

Q: How can I filter an ImageCollection by MGRS_TILE property?

A: You can use the filter method to filter an ImageCollection by MGRS_TILE property. The method takes a function as an argument, which should return a boolean value indicating whether the image should be included in the filtered collection. For example:

var collection = ee.ImageCollection('LANDSAT/LC08/C01/T1')
  .filter(ee.Filter.eq('MGRS_TILE', '30SNE'))

Q: What is the difference between filter and filterDate methods?

A: The filter method is used to filter an ImageCollection based on a condition, while the filterDate method is used to filter an ImageCollection by date range. The filter method takes a function as an argument, while the filterDate method takes two arguments: the start date and the end date.

Q: How can I combine multiple filters in anCollection?

A: You can use the filter method to combine multiple filters in an ImageCollection. The method takes a function as an argument, which should return a boolean value indicating whether the image should be included in the filtered collection. For example:

var collection = ee.ImageCollection('LANDSAT/LC08/C01/T1')
  .filter(ee.Filter.eq('MGRS_TILE', '30SNE'))
  .filterDate('2015-01-01', '2016-01-01')

Conclusion

In this article, we answered some frequently asked questions (FAQs) related to creating multiple ImageCollections based on date property in GEE. We hope this article has been helpful in understanding how to create multiple ImageCollections based on date property in GEE.

References

  • Google Earth Engine Documentation: ImageCollection
  • Google Earth Engine Documentation: Filter
  • Google Earth Engine Documentation: Map

Code

The code used in this article is available on the GEE Code Editor. You can access the code by clicking on the following link: GEE Code Editor

Note

This article is for educational purposes only. The code and examples provided are for demonstration purposes and may not be suitable for production use.