Satellite Images – Today, satellite imagery is one of the most popular features on Google Maps. Capturing the world from above is a huge undertaking, matching millions of images to precise locations. But how does satellite imagery actually work? What are some of the biggest challenges to bringing satellite imagery to more than 1 billion users?
How Google accumulates the images used in Google Maps? Do they actually use satellites?
The mosaic of satellite and aerial photographs you can see in Google Maps and Google Earth is sourced from many different providers. Including state agencies, geological survey organizations and commercial imagery providers. These images are taken on different dates. And under different lighting and weather conditions.
In fact, there’s an entire industry around doing aerial surveys. Companies cut holes in the bottom of planes, and cameras take pictures as they fly overhead. In many areas around the world, this is happening constantly. In parts of the world where there isn’t an established aerial survey market, Google rely on satellites.
With aerial surveys, they get very high-quality images that are sharp enough to create detailed maps. Satellites produce lower-quality imagery, but are still helpful because they provide global coverage.
How do the images meet the map?
Google obtains commercially-available satellite imagery from a range of third parties. And their team stitches the images together to create a seamless map. This process is called photogrammetry. They’re increasingly able to automate our photogrammetry process using machine learning to help accurately place images and improve resolution.
- For aerial data, the images are delivered on hard disks. And they upload them into Google Cloud.
- For satellite imagery, the data is uploaded directly from providers to Google Cloud.
The imagery is delivered in a raw format. It’s not yet positioned on the ground. And is separated into red, blue and green photos, as well as panchromatic images, which includes finer details. They then combine the jumble of images so they all line up and have an accurate placement in the real world, and generally look beautiful.
How often do Google update satellite images?
It depends on the area. For instance, because big cities are always evolving, they update satellite images every year. For medium-sized cities, they update images every two years, and it goes up to every three years for smaller cities. Overall our goal is to keep densely populated places refreshed on a regular basis and to keep up with a changing world, so they will refresh areas more frequently when they think there’s lots of building or road construction going on.
Why do we sometimes see mysterious objects on Maps? What are they?
One of the most common instances of this are “sunken ships,” which are actually regular, operating ships that might appear underwater due to the way the satellite imagery gets layered together. Other times, sunlight can reflect off something shiny, and it will look like a strange white object that some believe are haunted houses or other such spookiness.