NEAR mountpoint

The NEAR mountpoint provides corrections from the closest base station to your location.
Only declared bases, that are in the mounttable of the caster, are considered for the NEAR mountpoint.
1 km hysteresis is applied to avoid frequent switching between bases when moving around.
The NEAR4 mountpoint provides the same corrections as NEAR, but with a compact version of the RTCM3 messages, which reduces data consumption and improves stability of the connection. It is recommended to use NEAR4 for most applications, as it doesn't reduce accuracy whatsoever.

NEAR4

On the NEAR4 mountpoint, the NEAR stream's MSM7 messages are converted to MSM4 messages, which removes information such as
- Decimals on pseudoranges and carrier phases, which are already under the noise level of the measurements (<1mm)
- Decimals on signal strength (C/No), which are not useful for the rover
- Doppler information, which is useful only for extremely specific applications and not supported by most rovers
The resulting RTCM3 stream is smaller than the original MSM7 stream, which reduces data consumption and can improve stability of the connection

Observable	MSM4 Resolution	MSM7 Resolution	Notes
Fine Pseudorange	1/1024 m ≈ 0.0009765625 m (0.98 mm)	1/16384 m ≈ 0.000061035 m (0.061 mm)	MSM7 is 16× finer
Fine Carrier Phase	1/256 cycle ≈ 0.00390625 cycle	1/4096 cycle ≈ 0.0002441406 cycle	MSM7 is 16× finer
C/N0 (Carrier-to-Noise)	1 dB-Hz	0.0625 dB-Hz (1/16)	MSM7 allows finer signal strength reporting

Carrier phase resolution depends on signal wavelength. For example with GPS L1 (λ ≈ 0.19029367 m):

Observable	MSM4	MSM7
Carrier phase resolution	≈ 0.74 mm	≈ 0.046 mm

MSM7 provides 16× finer precision than MSM4 for pseudorange and carrier phase.
C/N0 precision improves from 1 dB-Hz → 0.0625 dB-Hz.

In real GNSS receivers, raw measurement noise is typically:
- Code: ~20–30 cm
- Carrier phase: ~1–2 mm

MSM4 already exceeds receiver noise for code measurements