KUON SKY satellite visibility simulator
The positioning satellites above you right now
Pick a point on the map and it works out which satellites stand above it at this moment. The ones cut off by surrounding hills are counted separately. Everything is computed in your browser, and the point you choose is never sent anywhere.
RTK base stations you can use here
Seeing the satellites is half of it. To resolve centimetres you also need corrections from a base station. These are open ones near you — no key, no fee.
Open at a place
What it computes
- Orbits. Orbital elements (OMM) from CelesTrak are refreshed every three hours and propagated with SGP4. Around 170 satellites across GPS, QZSS, GLONASS, Galileo and BeiDou.
- Terrain shadow. Elevation is sampled along 72 azimuths out to a 50 km radius to build the local horizon, and satellites below that line are removed. Earth curvature and standard atmospheric refraction are included. Elevation data: GSI 10 m class tiles in Japan, Tilezen/Mapzen elsewhere.
- Positioning geometry. HDOP, VDOP, PDOP and GDOP from the geometry of the visible satellites. Smaller values mean a position that resolves more readily.
- A 24-hour outlook. The PDOP curve over the next day, with the best 60-minute window marked.
- Elevation cutoff, adjustable from 0 to 30 degrees in 5 degree steps, so the count matches the setting on your own receiver.
What it does not compute
- Ionospheric and tropospheric delay are not included.
- Buildings and trees are not included. Terrain only.
- Multipath is not modelled.
- Being above the horizon is not the same as a receiver actually using that satellite. What you see here is geometric line of sight.
What PDOP value is good enough?
- DOP describes the geometry of the satellites, not the accuracy. Spread across the sky gives a small number; clustered together gives a large one. Smaller means the position is easier to resolve.
- The rule of thumb widely used in surveying: 1-2 is ideal, 2-5 is fine for most work, 5-10 may still be usable depending on what you need, and above 10 is not trustworthy.
- These are conventions the industry settled on, not an international standard. Where you draw the line depends on the accuracy you need. The same PDOP means different things for centimetre survey work and for a metre-level track log.
- And a low DOP does not guarantee accuracy. Ionospheric disturbance, multipath, the receiver itself, baseline length. All DOP can tell you is that the geometry is not the problem.
- This page plots PDOP across 24 hours. Read the shape rather than the number — where the troughs and peaks fall. The same spot can more than double between one hour and the next.
About Michibiki-7
QZS-7 (Michibiki-7), launched on 11 August 2026, is included. Its catalogue number is 100270, which is six digits.
The legacy TLE format has room for only five digits of catalogue number. A six-digit object does not fit the format at all, and CelesTrak returns nothing when asked for it as TLE. KUON now ingests orbital elements as OMM (JSON), so satellites launched from here on will not be missed for the same reason.
The orbit is still provisional. What you see is a satellite still drifting toward its assigned slot.
How to use it
- Open the map from the buttons above. The computation starts at the centre of the map.
- Click anywhere on the map to move the point and recompute.
- Move the elevation cutoff to decide whether low satellites count.
Sources
Orbital elements: CelesTrak (OMM) · Elevation: GSI elevation tiles (Japan, 10 m class, processed from GSI tiles) and Tilezen/Mapzen elsewhere · Propagation: SGP4