Satellite angle, remote sensing

• Firben
In summary: This formula is used to calculate the mean horizontal resolution in the direction of longitude. It is derived from the fact that the satellite is viewing a region centered at 60°N 0°E, which means that the longitude is changing as the satellite moves along its orbit. The formula takes into account the distance traveled by the satellite (d) and the angle of incidence (α) at each longitude.
Firben

Homework Statement

You have a geostationary satellite (location 0◦N 0◦E, 36000 km above geoid). Assume the Earth to be spherical with a radius of REarth = 6372km

When observing a region centered at 60◦N 0◦E:

What is the incidence angle of the satellite’s line of sight (at pixel center; surface parallel≡ 0 ◦ , nadir≡ 90◦ )?

φ = 60◦
r = 6370 km

The Attempt at a Solution

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http://s716.photobucket.com/user/Pitoraq/media/Rs_zpstcj5qby5.png.html?sort=3&o=0

Im not sure how to calculate the angle of incidence by that figure. This is from an exam and the solution is:

b = r × sin φ = 5517 km
a = r − r × cos φ = 3185 km
scan-angle (off nadir) β: tan β = b/(h+a) = 5517/(36000+3185) = 0.1408, β = 8.014◦
parallel surface: 90◦ − φ = 30◦
incidence-angle: γin = 90◦ − (φ + β) = 21.99◦

where do they get the relation 90◦ − φ = 30◦ from ? and where is β in my figure ?

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β is the acute angle on the far right of your sketch.

But where do they get the relation γin = 90◦ − (φ + β) = 21.99◦ from ?

I got the answer by using the sinus law (v = 21.9). But what about the mean horizontal resolution in direction, respectively (in km)? You might assume the Earth to be locally flat.
If i call the right side of the figure d,then d is = 41639 km
tan α(lon) × d × 2 = 2.89 km
Why did they add those terms together ?

Firben said:
But where do they get the relation γin = 90◦ − (φ + β) = 21.99◦ from ?
From there being 180° in a ∆. Your diagram is too small; you need a large, neatly drawn figure that is so spacious that you can imagine yourself walking around in it----that's how I view geometry.
γin needs to be shown measured against a tangent to the Earth's surface, so there's your 90° between a radius and that tangent.

Yes, i saw it when i plotted a new figure. But where do the relation tan α(lon) × d × 2 = 2.89 km came from ?

1. What is the purpose of satellite angle in remote sensing?

The satellite angle, also known as the viewing angle, is an important factor in remote sensing as it determines the perspective and coverage of the area being observed. A larger satellite angle provides a wider view of the Earth's surface, while a smaller angle allows for more detailed and higher resolution images.

2. How is satellite angle calculated in remote sensing?

Satellite angle is typically calculated using the satellite's position in relation to the Earth's surface and the sensor's field of view. This can be done using trigonometric formulas and satellite orbit data. Some remote sensing satellites also have adjustable viewing angles to capture different perspectives of the Earth.

3. How does satellite angle affect the accuracy of remote sensing data?

The satellite angle can greatly impact the accuracy of remote sensing data. A higher angle may result in more distortion and reduced resolution, while a lower angle may provide clearer and more precise data. It is important for scientists to consider the appropriate satellite angle for the specific purpose of their remote sensing study.

4. What are some factors that can affect satellite angle in remote sensing?

There are several factors that can affect satellite angle in remote sensing, including the satellite's orbit and altitude, the Earth's rotation, and the curvature of the Earth's surface. Other factors such as atmospheric conditions and cloud cover can also impact the satellite angle and the quality of remote sensing data.

5. How is satellite angle used in different types of remote sensing applications?

Satellite angle is a crucial aspect of remote sensing that is used in various applications such as land use mapping, environmental monitoring, and disaster management. In land use mapping, a larger angle may be used to capture broad areas, while a smaller angle can be used to identify specific features. For environmental monitoring, a consistent angle is important for detecting changes over time. In disaster management, different angles may be used to assess damage and facilitate rescue efforts.