How off-nadir imagery provides information and insight
The value of off-nadir imagery collections
“Nadir” and “off-nadir” imagery refer to a satellite’s angle in relation to its target at the time of collection. Collecting imagery from increasing angles stretches the pixel, so there is a direct relationship between off-nadir angle and the effective, usable resolution of the imagery collected.
We collect targets off-nadir, even if it means reduced resolution, because this provides more opportunities to collect a specific area of interest. A wider off-nadir angle range equates to wider ground coverage per pass—and with wider ground coverage comes more chances of a satellite passing over a target in a given time.
Off-nadir collections also provide extra imagery details and important insights on features often obscured from a top-down (nadir) view: tunnel entrances, sides of buildings or lettering on side of a ship, for example.
26 degrees off-nadir: details of front of reactor building
5 degrees off-nadir
Leading agility
Because of their larger aperture and agility, Maxar satellites have a much larger area over which they can observe a location, providing more opportunities to collect an area at a comparable resolution. We leverage this capability to extend the reach of the satellite, which is extremely important in capturing emerging conditions, such as natural disasters or conflict. As soon as a satellite is approaching such an event, we can task it to collect that area of interest. WorldView-3, for example, can change its point from San Francisco to Las Vegas in as little as 15 seconds.
From an altitude of 617 km above Earth, WorldView-3 was near Bermuda and approximately 1,200 km southeast of Washington, D.C., when it collected the image above.
Stats:
Collection time: 11:18 a.m. EDT | May 2, 2020
~62 degrees off-nadir
Slant range: 1,400 km
8,760 sq km in one image
~70 cm resolution
Rapid response to world events
Disaster response requires quick and current information, to keep victims and first responders as safe as possible in changing situations. Off-nadir imagery enables a rapid response to world events, as satellites quickly retarget from one area to another, with no need to wait for direct passage over an area of interest. These views also provide opportunities to image an area repeatedly in a short period.
Increased collection opportunities
Exclusive economic zones can extend 200 nautical miles from the coastline. Without physical borders to aid them, maritime enforcement agencies require near-real-time monitoring to quickly respond to suspicious or illegal activity. Off-nadir imagery expands imagery access and allows monitoring of high-priority targets by having variable times of collection. It significantly increases area collection and enables comprehensive coverage of larger areas of interest. Scroll over the image above to view the detail.
An intuitive visual perspective
Off-nadir imagery often provides stunning views of cities, landscapes and even rocket launches—depicting Earth the way it really is. Real-world data makes this perspective naturally easier to understand for analysts, journalists and decision-makers at all levels. Scroll over the image above to view the detail.
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