GROUNDLINK
Azimuth, elevation & range from any point on Earth to anything in orbit — on any date. STK-grade access reports: past, live and future, free in your browser.
Observer — type anything
Place names, decimal degrees, DMS, MGRS, UTM, ICAO / IATA airport codes, Maidenhead grid — auto-detected. Airport codes fill in field elevation automatically.
Altitude (m)
Horizon mask
Pick individual satellites or load whole constellations. Sweeps support up to 150 objects at once.
Mode
Live: the next 24 hours from now, plus a real-time in-view readout.
Start (UTC)
Stop (UTC)
Time step
Refraction
| Time (UTCG) | Azimuth (deg) | Elevation (deg) | Range (km) | Range-rate (km/s) |
|---|---|---|---|---|
| No report yet — compute access to fill this table. | ||||
THE REPORT PROFESSIONALS USED TO OPEN STK FOR
Consumer tracking sites stop at "when can I see the ISS tonight". Groundlink is the full ground-to-orbit geometry engine: pick any observer site on Earth, any tracked object or whole constellation, and any time window — past, live or future — and get the classic facility-to-satellite access report: in-view windows with rise/set azimuths, and a timestamped azimuth / elevation / range table with range-rate, in the exact format engineers have used for decades.
ANY DATE
Re-run a report from years ago or sweep next week. A continuously-growing historical element archive matches elements to the epoch you ask about — reconstruct exactly what was overhead when it mattered.
TYPE ANYTHING
Place names, decimal, DMS, MGRS, UTM, ICAO/IATA codes, Maidenhead grid — one box, auto-detected, altitude filled in for you from airport field elevation.
GNSS DOP, BUILT IN
Not just which navigation satellites are in view — GDOP / PDOP / HDOP / VDOP from the live GPS + Galileo + BeiDou + GLONASS geometry above your mask angle. No free tool computes this.
LIVE, NOT JUST PREDICTED
Live mode adds a real-time in-view readout — azimuth and elevation updating as the pass happens, with range-rate / Doppler for ham and ground-station users.
ACCURACY YOU CAN AUDIT
Every report states its element epoch and age. The engine is cross-validated against independent references to better than 0.01° — WGS-84 topocentric, refraction as an explicit toggle.
STK-STYLE OUTPUT
The exact facility-to-satellite AER access format engineers already know — copy-paste compatible, plus CSV and JSON downloads and shareable report links.
FREQUENTLY ASKED QUESTIONS
What are satellite look angles?
Look angles are the azimuth (compass bearing, measured clockwise from true north) and elevation (angle above the local horizon) from an observer on the ground to a satellite, normally reported together with range — the straight-line distance in kilometres. They tell you exactly where to point an antenna, telescope or camera at any moment.
How do I get azimuth, elevation and range from my location?
Enter your site in the box above — a place name, decimal or DMS coordinates, an MGRS or UTM grid reference, an ICAO airport code or a Maidenhead grid square. Pick one or more satellites (or a whole constellation), choose a window and step, and press Compute Access. You get in-view windows plus a full timestamped AER table you can export as CSV or JSON.
Can I compute look angles for a past date?
Yes — switch the time mode to Past. Groundlink keeps a historical element archive and matches elements to the epoch of your window, so you can reconstruct what was overhead from any site on a given date. The archive grows continuously; if a very old window has no archived elements yet, the report says so rather than guessing.
What is GNSS DOP?
Dilution of precision measures how the geometry of visible navigation satellites affects position accuracy: GDOP (overall), PDOP (3-D position), HDOP (horizontal) and VDOP (vertical). Groundlink computes them from the GPS, Galileo, BeiDou and GLONASS satellites above your mask angle at each step. Lower is better; under 2 is excellent geometry.
How accurate are the reports?
Angles are computed with standard SGP4 propagation in a WGS-84 topocentric frame, cross-validated against independent astronomy references to better than 0.01 degrees for fresh element sets. Accuracy degrades gracefully with element age — which is why every report prints its element epoch and age, so you can judge staleness at a glance. Atmospheric refraction is off by default (matching classic access reports) and available as a toggle.