The
approximate number of satellites orbiting the earth is 2666. These satellites
provide us the images of the earth which is known as Satellite Imagery. The
images are used for communication purposes, for observation of Earth, and for
navigation purposes. Governments and businesses around the world have ownership
rights of these satellites.
The
satellites are placed in 3 main orbits of the earth. They are classified as
low, medium, and high earth orbits. Majorly the commercial satellites use the
low orbit of the earth. The satellites placed in the middle orbit of the earth
help us with the imagery used for navigation. For weather conditions and
communication, we rely on the satellites placed in the high orbit of the earth.
Another
aspect of the satellite imagery one needs to consider is the resolution. The
resolution of the satellite imagery would vary as per the instrument used and
the position of the satellite in the orbit. There are five types of resolution
namely
·
The
spatial resolution simply termed would be the pixel size of the image
·
The
spectral resolution is the size of the wavelength interval
·
Temporal
resolution is the period between each imagery collection
·
Radiometric
resolution is the system resolution that captures the various level of
brightness
·
Geometric
resolution refers to the ability of the system to capture a part of Earth in a
single pixel
The
satellite imagery is used in various applications like fishing, landscape,
education, and more. The data captured from such satellite imagery is used by
various industries such as real estate, mapping, insurance, and others.
In the present times, we can have easy access to satellite imagery of Earth
through various portals. Few such imageries are free to download for research
and study purposes. One can opt for specific, high-resolution imagery through
paid sources as well. You can choose any of the online portals or sources that
give you satellite imagery as required by you. You can zero in your imagery
accurately once you are clear about the concept of Earth orbits and resolution.
Here we will list a few sources from where you can download free satellite
imagery of earth:
USGS
Earth explorer agency
USGS
holds a record for its collection of free satellite imagery which is over 40
years old. The images are made available through Earth explorer. They have
images from the USGS Nasa Landsat mission and data from ISRO, Sentinel-2, and
high-resolution images from OrbView-3. The search parameters help you to narrow
down your choice of imagery. It also has a feature-based search parameter to
help you identify the area as per the specialty of the location. You can
preview and download imagery using the Bulk Download application. For analysis
of the image, you need to have specific software. USGS Earth explorer has the
best and large collection of free satellite imagery. The only drawback is its
non-user-friendly menu options. An amateur will take time to familiarize
oneself with the buttons and available data-sets.
Landviewer
Landviewer
is the best satellite imagery source for free downloads. It offers updated free
images from Landsat 7-8, Sentinel-1, MODIS, aerial data from NAIP, and others.
It offers the best spatial resolution that is 40 cm per pixel. The search menu
parameters are user-friendly as it is easy and straightforward. You can easily
download full or cropped images in JPEG, KMZ, or GeoTIFF. The downloaded
imagery can be stored in the local PC or cloud storage. The best feature of
Landviewer is its analysis tool. You can use different band indices like NBR or
SAVI to analyze your free imagery download.
Sentinel Hub
You
can use Sentinel Hub source to access open-source satellite imagery. You can
either use EO Browser or Sentinel playground to download the imagery. It gives
you access to Landsat & MODIS imagery. It offers near-infrared best
resolution for imagery. it is a source that provides new images every 5 days.
However, a few imageries even at 10M lacks resolution and may not be ideal for
various applications. The downloaded imagery using Sentinel playground can be saved
in JPEG formats. EO Browser gives an option for analyzing the downloaded
images.
Google Earth
The
best resolution imagery is available with Google Earth. The imagery data is 3 –
4 years old. The imagery can be used only for non-commercial applications. You
will not be able to download the imagery.
NOAA
NOAA
gives you access to GEOS-R and NOAA-20 data. Since the satellites are located
in the high orbit of the earth, the imagery lacks good resolution. GEOS-R
refreshes data in approximately 15 minutes. This makes it closest to providing
real-time data. The imagery can be viewed in your browser. The usage of imagery
is strictly for non-commercial purposes.
UP42, Arcgis, and Aspectum
There
are new platforms in the market today that have enabled easy access to
satellite imagery such as UP42 (from Airbus), Arcgis Online (from esri), and
Aspectum. These platforms not only sell base imagery but also let you task
satellites to take custom images and run various analytical processing engines.
Conclusion
Aventior’s Satellite Image Analytics
(SIA) is
a platform that uses computer vision to detect objects, monitor changes, and
also map open spaces. It can be used for building detection, sports facilities
detection, vehicle detection, aircraft detection, and much more. Aerial &
Satellite Image Analytics (SIA) platform processes satellite imagery in RGB
mode. It is capable of processing images and videos with less than 55 cm
in resolution. Aventior offers one of the
best SIA platforms in various models as per your requirement. Aventior offers
its services in SaaS-based access, API-based data service, and Product
embedding. If you have any questions, please reach out to us at info@aventiors.com.
