This week’s guided exercise will give you an opportunity to compare different types of optical imagery from a range of different satellites.

For this exercise, we will use the Earth Images Lite tool from GeoCento.

Follow the steps below and then join the discussion to compare results and discuss ideas with other learners. Once you feel confident with the tool, you can explore other locations and data sets of your choice.

You may find it helpful to open the exercise in a separate window using a desktop computer or tablet device.

1. Go to Earth Images Lite. Type in ‘London’ in the location search box at the top of the ‘Select a place’ menu. Select ‘London, UK’ from the list that appears. This creates a square around London on the map.

2. Select ‘Optical Very High Resolution’ (‘Optical VHR’) from the ‘Select type of imagery’ drop-down menu.

3. Select ‘Sep 04, 2017 - Oct 04, 2017’ as the date range.

4. Click ‘Search’. The system will now search for Optical VHR images over London from several satellites taken in this date range. Thumbnail images of these results will appear on the left hand side of the page after a few moments.

5. To see an expanded ‘quick look’ view of the data, along with additional information, you can click on the double-square icon in the blue bar below each thumbnail. Try clicking on a few to see the level of detail available in the data. You can also familiarise yourself with the names of different satellites which have acquired this data, and see how many images are obscured by cloud.

6. Next, change the type of imagery to ‘Optical - high resolution’ or ‘Optical - medium resolution’ (which includes Sentinel 2) in the dropdown menu at the top of the page, and search again. Explore and compare the levels of detail visible in data from different satellites. (NB: Sentinel 2 is referred to as ‘medium resolution’ here (rather than high resolution) as the Earth Images platform includes very high resolution imagery available commercially. The advantage of Sentinel data is that it is available to anyone free of charge at its full resolution. Commercial data can normally only be downloaded at full resolution for a fee).

7. Once you feel familiar with the platform and different types of data, you can repeat this exercise with alternative locations. You can search for a location either by typing into the search box, or by drawing a polygon onto the map by selecting one of the polygon tools in the dropdown at the top of the page. (Remember not every location will have results in every resolution).

Once you’ve tried out this exercise and explored the tool further, you can share your thoughts and findings in the discussion below. In particular, you can add comments on anything you found surprising about the quality or detail in the imagery, or how hard or difficult you found it to compare data.

Remember, although Earth Images Lite is a very user friendly tool with selected data available, its interface and the way it presents results is similar to aspects of other more detailed tools used professionally in EO.

Take the end of week test

You can take the end of week test by clicking on the test button located on the top-right.