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How to create a Satellite Time Lapse Animation?

Time Lapse animation created from satellite imagery can give us sight of changes in earth over a period of time. Today we are going to generate a Time lapse animation using the Heroku web app. You can access this web app using this link. A window with a base map and few tools will be appeared.

1-2. From the toolbar, you can choose “Create timelapse”.

3. Then you can navigate to your Area Of Interest either by searching on the search bar in the top left corner of the screen.

4-5. After that, you can define your Area Of Interest, by drawing a rectangle using the drawing tools available on the left side of the screen.

6. Then from the toolbar appeared on the bottom right of the screen,

  • Choose a collection. Landsat TM-ETM-OLI Surface Reflectance, Sentinel-2AB Surface Reflectance and MODIS are the available collections. In this tutorial, I have chosen Sentinel-2AB Surface Reflectance.
  • If required, you can give it a Title. The default Title will be “Timelapse”.
  • Choose a band combination from the RGB dropdown
  • Choose frame per second. Minimum is 1 and Maximum is 30
  • Choose Start and End Years and Months
  • Options are available for cloud mask and Normalized Difference Index
  • Finally, click on the Create Time laps button
  • The time-lapse will be added to the screen.

7. You can download the time-lapse file by clicking on Click here to download time laps link.

Some of the Time lapse animations that we have created using Heroku web app can be seen below.

Bembla Dam- 2017-2021 generated using Sentinel-2 images

 

Island of Hawai’i 2010-2020 generated using Landsat Scenes

Download SRTM DEM Using Google Earth Engine Explorer

 

A Digital Elevation Model or a DEM is a 3 dimensional representation of the elevation of a terrain, usually in raster file format. Each cell in the raster represents the elevation of a specific area in the terrain. DEM can be used for various purposes such as Hydrological modelling, Terrain visualization and analysis, Engineering and Infrastructure Designs etc. Some of the most commonly used freely available DEMs are ASTER GDEM AND SRTM DEM. These data sets can be downloaded from official websites and a number of other websites. But one of the disadvantage of these websites are the users need to download a full tile of DEM, even if they need data for a relatively small area.

So today we are going to learn a way which allows the user to download data of their own area of interest using the Google Earth Engine Explorer. So what is earth engine explorer? The Google Earth Engine Explorer is a simple web application for exploring the huge amount of freely available geographic data stored in the Google Earth Engine Catalogue. The user can search for various types of earth observation datasets such as digital elevation models, weather data, climate data etc. The Google Earth Engine Explorer also allows the user to import, run simple analysis and save and export the result.

The steps to download SRTM DEM Using Google Earth Engine Explorer are as following

  1. Sign up to Google Earth Engine Explorer using your Google account here

  1. Zoom in to your area of interest by using the search bar or scrolling your mouse wheel
  2. Search for “NASA SRTM Digital Elevation 30m” in the search bar
  3.  Your search result will be added to the Table of Content on the left side of the screen. Also, a pop-up will be appeared on the screen. Here you can change options to get a better visualization of your area of interest

  1. Change the default visualization parameters using the palette option if required

  1. Click on download layer option
  2. Click on View port button to choose either polygon or rectangle to choose your area of interest
  3. Choose an appropriate file format. Also, if necessary, you can change the projection. Change the resolution to 30 m
  4. Click on download button to download your data

  1. Unzip your data and open it in your favourite GIS software for further analysis