What is a satellite image?

So you are interesting in downloading satellite images? Let's start from the top by defining a satellite image.

Satellite images or in a more scientific terminology, satellite remote sensing images, are data in the form of images that are collected using satellites in orbit around the Earth.

In terms of images we mean the recorded spectrum (reflected or emitted) of objects in a gridded format. This translates to a matrix with rows and columns which cover a specific geospatial extent. Each recorded spectrum is a different matrix.

So if we record the well known true color images, we have three matrices of equal dimensions. 

There are many remote sensing satellites orbiting the Earth, that capture different types of images.

We have 3 main types of satellites:

  1. Optical (multispectral and hyperspectral)
  2. Thermal
  3. Synthetic Aperture RADAR (SAR)

In every case there are commercial and "open"  satellites that provide images with different specifications.

In this article we will focus on the "open" satellites. With the term open, we mean satellites that provide data for free.

The European Space Agency (ESA) and the National Aeronautics and Space Administration (NASA) are two major providers of free and open data.

They have developed and operated the following satellites from where you can download images:

  1. Landsat (NASA)
  3. Sentinels (1-5) (ESA)

In the following videos we will show you how to download satellite images using different providers. All these videos are also part of our courses, so if you want to learn what to do after you have downloaded the images, just go to a specific course and enroll!

Download Landsat/Sentinel Images using the EOS LandViewer platform

Just the tip of an iceberg

In the above videos, we presented just some of many different ways to download satellite images. Many more satellites and online platforms are available to download satellite data. The next big step for you now is start learning how to process them!

About your Instructor

I'm a Remote Sensing and a Surveying Engineer. I received my degree from NTUA in 2010, where I also received my Ph.D. in hyperspectral remote sensing in 2016. From graduation in 2010, my career started as a Researcher Associate and Teaching Associate in the Laboratory of Remote Sensing of NTUA. From that time I also worked at several private companies as a Remote Sensing Expert and Geospatial Analyst. From the beginning of 2015 I was positioned as Senior Earth Observation Expert. During these years, I have participated in more than 20 funded European Commission and European Space Agency projects, have over 16 peer reviewed scientific publications in the field of Remote Sensing, and have an international patent in hyperspectral data compression.My main research and professional interests are in the optical remote sensing area, where I specialize in data (images, point measurements) processing and algorithm design and development. Some of the software tools that I operate to accomplish my research and business dreams are SNAP, ENVI, IDL, QGIS, ERDAS Imagine, ArcGIS, and Python. I have been working with these tools since 2008.

Dimitris Sykas

Remote Sensing Expert