Satellite look angle calculator
A look angle is the pair of numbers a dish needs to find a geostationary satellite: the azimuth, measured clockwise from true north, and the elevation above the horizon. Both follow from your latitude and longitude and from the satellite’s orbital slot. This calculator adds the slant range, the polarisation skew and the free-space path loss.
North positive, south negative.
East positive, west negative.
Starts on a free longitude, so any slot works. The named entries are a small selection of well-known positions, checked against CelesTrak element sets on 18 August 2026.
The only satellite coordinate you need. Geostationary satellites all sit over the equator, 35 786 km up, so there is no satellite latitude to enter.
C band ≈ 4 GHz, Ku band ≈ 12 GHz, Ka band ≈ 20 GHz.
Left, the compass rose. The needle sits on the computed azimuth and the shaded sector measures it clockwise from north, past the compass points on the rim. Right, the same path seen from the side. The dashed line is your local horizon, tangent to the Earth at your feet, and the ray to the satellite lifts off it by the elevation angle written at the arc. Below the horizon the ray turns amber and dashed: nothing on that bearing is visible from here. The side view is a schematic, not to scale.
Spherical Earth and a satellite exactly on its nominal slot. The ellipsoidal figure of the Earth and the station-keeping box of a real satellite each move the angles by a few hundredths of a degree, well inside the beamwidth of a domestic dish. Site altitude is ignored for the same reason: 1000 m changes the elevation by under 0.01°. Terrain is not covered at all, and a ridge on the bearing blocks the path whatever the geometry says.
How it works
- 01
Take the longitude difference
Subtract your longitude from the satellite’s orbital slot: Δλ = λsat − λsite, east positive. A satellite east of you gives a positive difference and an azimuth east of south in the northern hemisphere.
- 02
Find the central angle
The sub-satellite point is the spot on the equator directly under the satellite. The great-circle angle from your site to it follows from cos γ = cos φ · cos Δλ. Past γ = 81.3° the satellite is under your horizon and no dish can reach it.
- 03
Solve the triangle for range and elevation
Earth’s centre, your site and the satellite form a triangle with two known sides: Re = 6378 km and r = 42 164 km. The law of cosines gives the slant range, and the angle between the ray and your local horizon is the elevation.
- 04
Turn the dish to the azimuth
The azimuth is the great-circle bearing from your site to the sub-satellite point, measured clockwise from true north. A magnetic compass points at magnetic north instead, so add the local declination before you use one.
- 05
Set the skew last
A linearly polarised feed also has to be rotated, because the satellite’s polarisation plane is tilted relative to your local vertical. The skew angle is small on your own meridian and grows as the satellite moves east or west of you.
Formulas
- cos γ = cos φ · cos Δλ — central angle site to sub-satellite point
- φ — site latitude, degrees; Δλ = λsat − λsite
- Re = 6378.137 km — Earth equatorial radius
- r = 42 164.17 km — geostationary orbit radius
- el — degrees, negative when the satellite is below the horizon
- Re / r = 0.15127 — the same ratio sets the 81.3° visibility limit
- az — normalised to 0–360°, valid in both hemispheres
- skew = atan2( sin Δλ , tan φ ) — feed rotation, defined modulo 180°
Worked example
- Δλ = 19.2° − 8.54° = 10.66°
- cos γ = cos 47.38° · cos 10.66° = 0.6654, so γ = 48.28°
- d = 6378.1372 + 42164.172 − 2 · 6378.137 · 42164.17 · 0.6654 = 38 218 km
- el = atan2(0.6654 − 0.1513 , 0.7464) = 34.6°
- az = atan2(0.1850 , −0.7232) = 165.7°, just east of south
- FSPL at 12 GHz over 38 218 km: 205.7 dB, one-way delay 127.5 ms
FAQ
- Why does the calculator ask only for the satellite’s longitude?
- Because a geostationary satellite has no latitude worth entering. An orbit only holds still over one spot on the ground if it lies in the equatorial plane at a radius of 42 164 km, which is 35 786 km above the equator. Every geostationary satellite therefore sits on that one ring above 0° latitude, and the orbital longitude is the only thing that separates them. Satellites in inclined, medium or low orbits drift across the sky and need a full orbit propagator, which this page does not do.
- Why does the dish point lower the further north I live?
- Because the satellite stays over the equator while you move away from it. On the satellite’s own meridian the elevation drops from 90° at the equator to 32.7° at 50° N and 21.9° at 60° N. Beyond a central angle of 81.3° it reaches the horizon and disappears, which is why geostationary reception fails in the polar regions.
- Is the azimuth measured from true north or magnetic north?
- True north. A hand compass reads magnetic north, which differs from true north by the local magnetic declination, anything from a fraction of a degree to more than 20° depending on where you are. Add the declination to the calculated azimuth before you sight along a compass, or use a phone app that already corrects for it.
- Can I still receive a satellite at 5° elevation?
- Sometimes, but it is the hardest case. The signal crosses far more atmosphere, so rain fade is worse, the antenna picks up warm ground noise, and terrestrial transmitters on the same bearing interfere more easily. Anything on the horizon, a hill, a roof, a tree line, blocks the path outright. Above 10° a link is much better behaved.
- Why is the slant range longer than 35 786 km?
- 35 786 km is the altitude above the equator, which is the distance only from the sub-satellite point directly beneath the satellite. Every other site looks along a slanted path around the curve of the Earth. The range grows to 38 218 km from Zürich to Astra 19.2° E and reaches about 41 700 km at the horizon.
- What is polarisation skew and when does it matter?
- It is the rotation a linearly polarised feed needs so its horizontal and vertical planes line up with the satellite’s. It matters for linear Ku-band services such as Astra or Hot Bird, where a few degrees of error leak the other polarisation into your receiver. Circularly polarised systems, including most North American DBS, need no skew at all.
Geometry tells you where the satellite is. Whether a ridge, a roof or a tree line stands on that bearing is a terrain question, and Waveshed answers it on real elevation data, free in your browser.
Check the bearing on the map →Related guides
- Elevation profile & measuring tools — the simulator reports bearings from true north, the same convention as the azimuth here
- Antenna patterns & the sensor panel — how tight your pointing has to be depends on the beamwidth of the dish
Sources & further reading
- T. Soler & D. W. Eisemann, “Determination of Look Angles to Geostationary Communication Satellites” ↗ — Journal of Surveying Engineering 120(3), 1994, hosted by the NOAA National Geodetic Survey. Derives the spherical formulas used here, and the ellipsoidal refinement they approximate
- Eutelsat / TU München TD-1205-a, “Calculation of Azimuth, Elevation and Polarization for non-horizontal aligned Antennas” ↗ — operator pointing document that works from the same orbit radius of 42 164.2 km and covers the polarisation angle
- T. Pratt, C. Bostian & J. Allnutt, Satellite Communications, 2nd ed., Wiley 2003 ↗ — the textbook derivation of look angles from spherical trigonometry, chapter 2. Wiley has retired the page for the 2nd edition, so the link opens the current 3rd edition (Pratt & Allnutt, 2019), which keeps the same geometry in chapter 2
- CelesTrak — Active Geosynchronous satellites, with orbital longitudes ↗ — source of the orbital slots in the satellite list. Every longitude was checked against this table on 18 August 2026 and recomputed from the underlying element sets. The catalogue itself is public US Space Force data that CelesTrak redistributes, so no attribution is required
- Geostationary orbit — Wikipedia ↗ — orbit radius 42 164 km, altitude 35 786 km above the equator
Related tools
Parabolic dish gain calculator
Gain, beamwidth and effective aperture of a dish from diameter, frequency and efficiency.
Free-space path loss calculator
Signal loss over distance for any frequency, from the FSPL formula.
Horizon mask calculator (ridge elevation angle)
The elevation angle a ridge blocks, and whether GPS, satellite messengers or a GEO satellite still clear it.
Doppler shift calculator
Frequency shift from relative motion, for mobile and satellite links.