Lesson 6: Satellite Imagery Basics¶
Planning question: What does the city look like from space?
Free satellite images show any city as it is today. You will search the Sentinel-2 catalogue, choose a cloud-free image of central Bengaluru, make true and false colour images, and compare the spectral signatures of water, trees and buildings.
What you will learn¶
- Search a STAC catalogue by place, date and cloud cover
- Load satellite bands as an xarray dataset
- Convert raw values to reflectance
- Make true colour and false colour composites
- Plot spectral signatures
Key concepts¶
- Bands: each records one colour of light
- Reflectance: the share of sunlight bounced back
- False colour: showing invisible light, such as near-infrared, to reveal vegetation
What you will make¶
True colour and false colour images of central Bengaluru, and a spectral signature chart.
| Packages | pystac-client, odc-stac, rioxarray |
| Data | Sentinel-2 L2A (Microsoft Planetary Computer) |
| Time | 30 to 45 minutes |
Try it yourself¶
The end of the notebook includes these exercises:
- Compare 2019 with 2024.
- Move the box to the airport.
- Add a point for Bellandur Lake.
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