Satellite images are one of the most popular features of
Google Maps today. Capturing the world from above is a painstaking task with
the goal of matching millions of images with precise locations. But how do
satellite images really work? How often are these images updated? What are the
biggest challenges in delivering satellite imagery to more than 1 billion
users?
The mosaic of aerial and satellite imagery that you see on
Google Maps and Google Earth comes from many different providers, including
government agencies, exploration organizations, and commercial imagery
providers. These images were taken on different dates and under different
lighting and weather conditions. terms.
Google Earth is a platform that allows you to explore
more than 36 million square miles (1 m² = 2.59 km²) of high definition
satellite imagery from a variety of providers,
covering more than 98% of the total population, to see the
world from above. While these stunning photos show us parts of the world that
we may never visit, they also help Google Maps accurately simulate a world that
changes every day.
There is a whole industry around aerial photography.
Companies are placing devices on the underside of planes, and cameras are
taking pictures as they fly over a target. This happens all the time in many
parts of the world.
In places where the market for aerial photography is not
well established, satellites are used. With aerial photography, you get very
high-quality images, sharp enough to create detailed maps. Satellites provide
lower quality images, but are still useful as they provide global coverage.
Google Maps - Myanmar
Google obtains commercially available satellite images from
various providers, and their team combines the images to create the perfect
map. This is a process called photogrammetry that is automated using machine
learning to help accurately position images and improve resolution.
These images show us critical details about an area such as
roads, lane markings, buildings, and rivers, as well as the exact distance
between each of these features. All this information is collected without the
need to go to the site.
With improvements in photogrammetry techniques over the past
10 years, Google can align images from multiple sources (street views, aerial
and satellite imagery, and authoritative data sets) within one meter.
Over the past 15 years, Google has provided maps for more
than 220 countries and territories and displays useful information for more
than 200 million places.
How often do you update satellite images?
Google's goal is to update satellite images of the places
that change the most. For example, because big cities are constantly evolving,
they try to update satellite images every year. For medium-sized cities, they update
the images every two years, and for small cities, every three years.
The overall goal is to regularly update the densely
populated areas and keep up with the changing world, so the areas are updated
more frequently when considering that there are many buildings there or roads
are being built.
Why do we sometimes see mysterious objects on Maps?
Google engineers explain that sometimes the way images are
collected can create optical illusions. One of the most common cases is
"shipwrecks", which are actually sailboats that can appear underwater
due to the way satellite images are grouped into layers. In other cases,
sunlight can bounce off something bright and it will look like a strange white
object that some people associate with haunted houses or other spooky things.
The mapping never ends and there is constant work to create new tools and techniques
that will make image collection faster, more accurate, and safer for everyone.
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