Creating payload applications for satellites means you need test images from space. But, getting these images can be really expensive. They can cost a few thousand dollars each, and even more if you need very detailed or special kinds of images – sometimes more than tens of thousands of dollars. This makes it hard for many people to buy these images, especially when they're just starting to develop their payload applications.
Also, these satellite images come in different formats, like JPEG 2000, PNG, and GeoTIFF, depending on who's giving them and what you need them for.
In this blog, I'm going to show you how to get JPEG 2000 and PNG images for free, which you can use for testing your own payload applications.
Copernicus Browser
If you're looking for JPEG2000 data, you might find it on Copernicus Data Space Ecosystem - Copernicus Browser.
Previously, it was possible to search via the Copernicus Open Access Hub, but its operations ended at the end of October 2023. Copernicus Sentinel data are now fully available in the Copernicus Data Space Ecosystem. This new service provides not only access to a wide range of Earth observation data and services but also offers new tools, a GUI, and APIs to support the exploration and analysis of satellite imagery.
The primary goal of the service is to ensure instant data availability to users. The full data archive acquired by the Copernicus Sentinel satellites will be available online and can be accessed in real-time.
License
The data will be available free of charge via designated quotes for individual use. Users that wish to build large scale operations can use practically unlimited resources available under commercial terms. (Ref - About the
Copernicus Data Space Ecosystem)
How to download data
1.Open Copernicus Browser in a new window or tab.
2.Register or log in.
3.Zoom in on somewhere you like on the map with the scroll wheel of your mouse.
4.Specify the data criteria via Search tab:
- Select the satellite (as of Nov 2023, Sentinel-1, Sentinel-2, Sentinel-3, Sentinel-5P and Sentinel-6 are supported. Please refer to the documentation about data)
For instance, if you select Sentinel-2,
- Select the MultiSpectral Instrument (MSI): L1C(Level-1C) and L2A(Level-2A). (Ref - Sentinel-2 MSI User Guide - Product Types)
- Specify cloud cover percentage (e.g., 100% for all images, 50% for images with less than 50% cloud cover)
- Select the Auxiliary Data File: AUX_GNSSRD, AUX_PROQUA and AUX_POEORB. Please refer to Sentinel-2 Precise Orbit Determination (POD) products.
- Observation date/time range
Here is the comparison between L1C and L2A (Ref - Sentinel-2 MSI User Guide - Product Types)
| Type | Code | Description | Users | Production & Distribution |
|---|---|---|---|---|
| User Product | Level-1C | Top-of-atmosphere reflectances in cartographic geometry | All Users | Systematic generation and online distribution |
| User Product | Level-2A | Atmospherically corrected Surface Reflectances in cartographic geometry | All Users | Systematic generation and online distribution |
5.Select from the list or map.
6.Click on the download icon for the desired image.
If you would like to try more advanced search, please refer to the Product Search page.
Kaggle
If you're looking for PNG data, you might find it on Kaggle.
Kaggle is a platform primarily known for hosting data science competitions but offers much more, including a vast repository of datasets, a public data platform, and an online community for data scientists and machine learning practitioners. It was acquired by Google in 2017 and is part of the Google Cloud suite of services.
License
Regarding copyright of the data on Kaggle, it varies depending on the dataset. Each dataset on Kaggle comes with its own licensing terms, set by the dataset provider. These terms specify how the data can be used, and they can range from completely open and free for any use (like those under the Public Domain or Creative Commons licenses) to more restrictive terms that might limit use to non-commercial purposes or require attribution. It's important to note that just because data is accessible on Kaggle, it does not automatically mean it's free of copyright or restrictions on use.
How to download data
Here are some examples of Kaggle Dataset you might want to check.
| Dataset | Image Format | Number of Data | License |
|---|---|---|---|
| Ship Detection from Aerial Images | PNG | 621 (with ship) | CC0: Public Domain - No Copyright |
| Ships in Satellite Imagery | PNG (80x80 RGB images) | 1000 (with ship), 3000 (without ship) | CC BY-SA 4.0 |
Need to purchase satellite images for testing?
Some might wonder if free satellite images are sufficient for testing purposes. However, upon conducting actual searches, you'll realize that finding images that meet specific and detailed criteria can be extremely challenging. For instance, let's say you need satellite images taken near a port, where several ships are visible on the sea, with a cloud cover of around 30%, and even airplanes in the sky. Searching for such images using the tools mentioned above can be a time-consuming task, or you might not find them at all.
As the time to deploy your payload application to the satellite approaches and you need to test it with more detailed test cases, you may need to consider purchasing expensive satellite images.
Conclusion
To wrap up, making payload applications for satellites doesn't have to be expensive when it comes to getting test images. This blog has shown you how you can easily get JPEG 2000 and PNG images without spending a lot of money. You can use the Copernicus Data Space Ecosystem to get a wide variety of free Sentinel satellite images, which is great for anyone needing fresh and different types of images. Also, Kaggle is a good place to find different datasets, including PNG images, where you often don't have to worry much about copyright because of flexible licensing.
These resources are a big help in cutting down costs for satellite images. They open up more chances for creative work in making payload applications, whether you're experienced or just beginning. With these platforms, you have access to lots of data for your projects, making it easier to work on satellite-based applications without worrying about high costs.
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