Data acquisition


Learning goals

  • Visit the EarthExplorer platform
  • Query the Landsat archive
  • Download Landsat data

Background

Acquisition of remotely sensed data

The Earth’s atmosphere, water, and land surfaces are being observed by a plethora of instruments constructed for varying purposes. The technical properties of these instruments vary broadly and as a result, the data retrieved from such instruments also contains diverse types of information in various data types and formats. These raw datasets often require additional processing using automated algorithms which make them useful for communities with different applications at hand. But how is the data made accessible to the users?

Public institutions such as the United States Geological Survey (USGS) and the European Space Agency (ESA) play a key role in this regard, as they currently host the most relevant platforms for Earth Observation data distribution - the USGS Earth Explorer and ESA´s Copernicus Open Access Hub. Most (but not all) of the data provided on these platforms are currently available free of charge.


Assignment

1) Initial query

Let’s get some Landsat data. Check this website to get an overview of the Landsat Collection 1 products and processing levels.

Note: Landsat Collection 2 has recently been released. This represents a reprocessing of the entire Landsat archive to include recent advancements in data processing and algorithm development. In the future Collection 2 will replace Collection 1 and some changes, e.g. in quality bands, will require you to revise workflows built on Collection 1 data. However as this transition is ongoing we will still utilize Collection 1 data for this course.

Visit the USGS Earth Explorer and use the Address/Place field to navigate to Wisla, Poland (lat, lon: 49.6473, 18.8677). Switch to the ‘Data Sets’ tab and select Landsat -> Landsat Collection 1 Level-1. Tick the ‘Landsat 8 OLI/TIRS C1 Level 1’ box and click on ‘Results >>’.

2) Add search criteria

You´ll get several hundreds of results, so let´s narrow down the search. Under ‘Search Criteria’, define an acquisition date range between 01 February 2014 and 01 August 2014. Switch to the ‘Additional Criteria’ tab. Let´s choose a scene cloud cover of ‘Less than 40%’, and select the ‘Tier 1’ category.

Find the following images and visualize them in the Earth Explorer interface by clicking on the small image icon:

  • LC08_L1TP_189025_20140716_20170421_01_T1
  • LC08_L1TP_189025_20140310_20170425_01_T1

3) Order / download data

For downloading the data, you need to create an EarthExplorer account. You may register and download the .tar.gz files to your local machine. If you prefer not to register or you experience any problems, please download the files from our repository. Unpack the files in your session directory.



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