Importance of Unlocking the Potential of Free Satellite Imagery: Types, Uses, Sources

Forest fires, melting glaciers, and migrating birds — satellite imagery provide a wealth of useful information. It’s needed to learn about natural disasters, monitor fields, track deforestation and water levels, map urban development, and perform infrastructure planning. Free high-resolution satellite imagery is used by intelligence services of different countries, and journalists need them to follow the movement of refugees. But before we zoom in on the possibilities satellite pictures offer today, let’s see what types of those are actually used the most.

Types of Satellite Images

Modern technology enables users to get free satellite imagery online fast and easily. But first, it’s important to understand what type of image is needed. According to the spectral range, satellite pictures are divided into three main groups:

• images in the visible and near-infrared (light) range
• images in thermal infrared band
• images in the radio range.

Different spectral resolutions are used depending on the object and goal of the research. Further division is connected with the properties of images, determining their decoding possibilities, first of all with scale, visibility (territorial coverage) and resolution. The complex of these parameters characterizes the imaging conditions, the spacecraft used, the orbit altitude and other parameters.

Main Uses of Satellite Imagery

Satellite imagery is important for geographic research. From these images, comparisons can be made between data from a certain area in the past and recent information resulting from transformations occurring in geographic space.

Satellites are a unique tool for observing the planet, through them we can observe remote areas such as the Arctic. They can provide data not only on ice extent but also on ice thickness, an element of assessment and prediction of the evolution of the glacier system in the Arctic and Antarctic.

Overall, the main applications of remote sensing include:

• creating maps with a variety of data (cartography): geography, topography, hydrography, relief, vegetation, etc.;
• monitoring the use of natural resources;
• creating or updating maps in real time, and GPS;

Meteorological satellites are also an important tool for modern meteorology because they can retrieve altitude data and cover remote areas over oceans and continents, making a crucial contribution to better understanding and quantifying phenomena and parameters relevant to weather forecasting.

Sources of Free Satellite Images

Depending on their needs, users can choose one of the many sources of satellite imagery for just browsing, downloading, analyzing, or all of it. The prices usually differ depending on functionality and picture resolution. Let’s go through some of the most popular among such platforms.

EarthCache

EarthCache offers satellite imagery from such big providers as Planet, Airbus, and open data sources. The users are able to buy and download pictures of a particular area.

Google Earth

Google Earth enables access to high resolution satellite imagery, and ultra high resolution pictures taken from planes. To see how the planet is changing, users can take advantage of Google Timelapse tool for free.

Sentinel Hub

Sentinel Hub is one of the most popular sources of satellite data. Here users have access to all currently available Sentinel products, including historical satellite images. Apart from this, Sentinel Hub provides access to MODIS and Landsat products.

Earth Explorer

Earth Explorer is a platform where users can access Landsat satellite pictures, some of which are decades old. Earth Explorer also provides access to imagery from MODIS, SPOT, IKONOS, OrbView 3, and some Sentinel-2B products.

NOAA

NOAA portal provides free access to GEOS-R and NOAA-20 data. More so, new GOES-R data is available every 15 minutes, which makes it the closest to real time satellite images for free. However, the resolution of those images will be 250m and above due to satellites being located very far from the Earth’s surface.

Free Satellite Images by EOSDA LandViewer

EOSDA LandViewer is a catalog of satellite imagery available for analysis and download for various purposes. The platform enables comfortable search, analysis, storage, and download of different satellite pictures based on users needs.

EOSDA LandViewer online tool allows users to get free real time satellite imagery from a variety of satellites, including Landsat 7-8, MODIS, Sentinel-1 and 2, CBERS-4, Landsat 4-5 historical imagery, and more. You can also freely search and preview high-resolution satellite images (up to 40 cm per pixel) to pick the ones you want to purchase. Those include data from Pleiades-1, SPOT 5-7, SuperView-1, and Kompsat-2, 3, 3A.

As for the imagery search, it’s pretty simple and starts with defining the area of interest (AOI). This can be done through uploading a file, selecting the type of sensor and picking the dates. Apart from defining the area, users are able to apply filters: AOI coverage %, cloud cover %, and Sun elevation.

So, what about downloading? Let’s see how this works in an example. Imagine you want to download free Landsat images. First option is download a free full picture or manually cropped Natural color Landsat image in JPEG, GeoTIFF, or KMZ format. The second option is to download only specific spectral bands you will actually use. And the last option is to download an already processed image: a calculated index or a band combination.

Since EOSDA LandViewer is more than just a satellite imagery catalog, it also enables on-the-fly visualization and analysis of the chosen data. To help extract valuable insights from pictures the tool offers default band combinations and indices, clustering, time series analysis, and more. EOSDA LandViewer is a great helper for both GIS expats and beginners from different industries.