Quality Scale

The Quality Scale represents the quality of the data from a base station that is sent to the onocoy system. The grading system is based on clients' needs and combines multiple parameters into one Quality Scale score.

The overall Quality Scale is the product of the three factors constellation reward, band reward and signal quality reward.

Constellation reward

The constellation reward grades a base station regarding the featured GNSS constellations. It is the sum of each supported constellations factor. GLONASS is down-weighted and regional systems (IRNSS, QZSS) are not considered.

Constellation	Weight	Factor
GPS	1	0.286
GLONASS	0.5	0.142
Galileo	1	0.286
BDS	1	0.286
QZSS	0	0
IRNSS	0	0

Example Base station A features the constellations GPS, Galileo, BDS and QZSS. The resulting constellation reward is

Constellation reward = 0.286 (GPS) + 0.286 (Galileo) + 0.286 (BDS) + 0 (QZSS) = 0.858

Band reward

The band reward grades a base station regarding the featured frequency bands. It is determined by a maximum number of different frequency bands tracked on a constellation.

Number of bands	Scale factor	Description
1	0.08	L1 (typically), but could also be L5 only
2	0.32	L1/L2 or L1/L5
3	0.80	L1/L2/L5
4	0.95	L1/L2/L5/L6
5	1.0	Five frequency receivers.

Example The receiver from base station A offers the frequencies GPS L1/L2/L5 and Galileo E1/E5b/E5a/E5ab/E6 as well as BDS B1I/B2I/B3I/B1C/B2a/B2b/B3. It is hence considered as a quadruple-frequency receiver.

Band reward = 0.95 (quadruple band)

Signal quality reward

The signal quality now represents the quality of the actual electromagnetic signal that is being received and sent to the onocoy system. We calculate the average square of these four parameters:

• Root Mean Square (RMS) Code: The RMS Code is calculated from the Multipath Linear Combination. It factors in how much the surroundings of the base station cause the signal to be interfered.

• RMS Phase: The RMS Phase is calculated from a detrended Geometry Free Linear Combination. It helps to analyse the quality of the carrier phase signal.

• Cycle slip ratio: The cycle slips ratio is the ratio between the number of detected cycle slips and the total number of measurements. A cycle slip is a temporary loss of lock in the receiver and can cause losing a fix at the rover receiver.

• Sky visibility: The sky visibility represents the ratio between the number of observed satellites and the number of theoretically possible satellites based on the satellites' orbits. Satellites close to the horizon (below 10° elevation) are excluded from this analysis. Take a look at your sky view in the explorer to monitor your sky visibility.

Example Let's assume base station A gets the following scores:

RMS Code = 0.92
RMS Phase = 0.95
Cycle slip ratio = 0.98
Sky visibility = 0.67

The resulting signal quality results to, using the average square

$$SignalQuality = \frac{RMSCode^2 + RMSPhase^2 + CycleSlipRatio^2 + SkyVisibility^2}{4}=0.79$$

Example Taking all the values above, the overall Quality Scale for base station A then is

Quality scale = 0.858 (constellation reward) 
                * 0.95 (band reward) 
                * 0.79 (signal quality reward)
              = 0.64  

The overall Quality Scale of 0.64 will then be combined with the Location Scale and Availability Scale to calculate the final rewards.

Measurement to reward function mapping table*

	0.80	0.90	0.99+
Cycle-slip occurrence	1 in 150	1 in 1000	<1 in 2300
Pseudorange noise (code rms)	0.4m	0.28m	<0.14m
Carrier Phase noise (phase rms)	0.004m	0.0028m	<0.0014m
Sky visibility (% of tracked satellites with elevation > 7 degrees)	80%	90%	>99%

(*) Additional components of the signal quality are planned to be added in order to improve the quality assessment of both the device and the installation.