Telemetry & Protocols

What Data Does a GPS Receiver Provide?

Most users think a GPS receiver only outputs latitude and longitude. In reality, a satellite receiver is a sophisticated telemetry engine providing timestamps, velocity vectors, Dilution of Precision metrics, and individual satellite signal-to-noise ratios. Learn how structured coordinates differ from raw NMEA 0183 sentences.

1. Structured Location Telemetry

Key parameters unpacked from satellite radio bursts.

Latitude & Longitude Geodetic angular coordinates referenced to the WGS84 ellipsoid.

Altitude (MSL) Elevation in meters above Mean Sea Level or WGS84 geoid.

Speed Over Ground Calculated velocity from Doppler shift and time-difference vectors.

Course / Bearing True track angle in degrees (0° to 359.9°) relative to True North.

HDOP / VDOP Horizontal and Vertical Dilution of Precision indicating constellation geometry.

Satellites in View Number of visible space vehicles currently tracked and locked.

Atomic UTC Time Sub-millisecond atomic clock timestamp synchronized to GPS week.

Fix Quality Fix status: 0 = Invalid, 1 = Standard GPS, 2 = DGPS / SBAS, 4 = RTK Fixed.

Serial Standard

2. Raw NMEA 0183 Sentences Explained

The National Marine Electronics Association (NMEA) 0183 standard is the universal ASCII serial text protocol emitted by nearly all GPS modules (u-blox, MediaTek, SiRF).

$GNGGA,123519.00,4807.038,N,01131.000,E,1,08,0.9,545.4,M,46.9,M,,*47

$GNRMC,123519.00,A,4807.038,N,01131.000,E,022.4,084.4,280926,,,A*7B

$GNRMC (Minimum Navigation): Status Active | Speed 22.4 knots (41.5 km/h) | Heading 84.4° True | Date 28 Sep 2026

$GPGSV,3,1,12,01,40,083,46,02,17,308,41,03,07,243,33,06,27,118,43*7D

$GPGSV (Satellites in View): Message 1 of 3 | 12 visible satellites | Satellite PRN #1 at 40° elevation, 83° azimuth, 46 dB-Hz signal strength

3. Why Mockery Supports Structured & Raw Formats

Different applications require different levels of depth:

Standard Consumer Mobile Apps General navigation and delivery apps only care about structured numbers: location.latitude and location.speed. Mockery parses these directly into Android Location objects.

Specialized Surveying & Marine Apps Aviation, marine chartplotters, and GIS surveying tools listen to Android's OnNmeaMessageListener to evaluate signal integrity. When paired with Mockery GPS ESP, raw NMEA strings can be forwarded intact.

Design Principle: Never Fabricate Unavailable Data. If a provider does not know the satellite count, Mockery passes null rather than converting it to 0. Telemetry integrity is strictly preserved.

Connect Hardware Telemetry with Mockery

Stream raw NMEA sentences from an external ESP32 or simulate clean movement vectors from your browser.

Explore Mockery GPS ESP → Launch GPS Controller