Fix vs float, and why you lose a fix

Your controller shows a status word. It tells you how good your position is right now.

• SINGLESingleNo corrections at all. Your position could be off by several meters.Full definition: no correctionsCorrectionsLive info from a base station about how far off the satellite signals are, so your rover can cancel out the error.Full definition at all. You are off by meters.
• FLOATFloatA middle RTK status. Corrections are coming in but the math isn't finished, so you're only good to about a foot.Full definition: corrections are coming in, but the receiver hasn't finished its math. You are off by roughly a foot (decimeters).
• FIXFixThe best RTK status. The receiver has finished its math and your position is good to a couple of centimeters.Full definition: the math is done. You are within a couple of centimeters.

Here is what "the math" means. NGSNGSNational Geodetic Survey. The part of NOAA that runs the official US coordinate system, CORS and OPUS.Full definition's guidelines explain that the roverRoverThe receiver that moves around the job, like a survey pole or a drone. It uses the base's corrections to find its exact spot.Full definition first makes a rough guess at how many signal waves sit between it and each satellite. That guess has decimals in it, which is the float stage. Then it locks in the exact whole numbers. That is the fixed stage. Only a fix gives you centimeter-level positions.

What knocks you off a fix

• Blocked sky: trees, buildings and hills hide satellites. Fewer satellites, bunched together, make weaker geometry. Your receiver shows this as PDOPPDOPA score for how well spread out your satellites are. Lower is better. Satellites bunched in one part of the sky give a high, bad PDOP.Full definition (a higher number is worse).
• MultipathMultipathWhen a satellite signal bounces off a wall, truck or water before it reaches you, like an echo. It throws off your position.Full definition: signals bouncing off walls, trucks or water before they reach you, like an echo.
• Elevation maskElevation maskA setting that ignores satellites lower than a chosen angle above the horizon, because low signals are noisy.Full definition: satellites low on the horizon are noisy. NGS suggests ignoring anything below 10 to 15 degrees.
• BaselineBaselineThe distance between the base station and your rover. Shorter is better for accuracy.Full definition length: the farther you are from the base, the more the air above you differs from the air above it. See Baseline length.
• Weak internet link: slow or dropped cell data. Watch the "age of correctionsAge of correctionsHow old the latest correction message is, in seconds. If it keeps climbing, your internet link is struggling.Full definition" number. If it keeps climbing, the link is the problem.
• Wrong mount pointMount pointOne specific correction stream on a caster, like one channel on a radio. Each one comes from a certain station or network setup.Full definition: a channel that doesn't send the satellite systems or signals your receiver uses.
• Space weather: activity in the ionosphereIonosphereA high layer of the atmosphere charged by the sun. It slows down GPS signals and can make getting a fix harder.Full definition (a high layer of the atmosphere) can slow down or block a fix.

Still stuck on float? Go through Troubleshooting no-fix.