@jbroll/nmea-simple/prn-utils.ts

NMEA 0183 sentence parser and encoder

// Map talker IDs to system IDs according to uBlox NMEA 4.1 spec
export function getTalkerSystemId(talkerId: string): number {
    switch (talkerId) {
        case "GP": return 1;  // GPS
        case "GL": return 2;  // GLONASS (primary)
        case "GA": return 3;  // Galileo
        case "GB": return 4;  // BeiDou
        case "GQ": return 5;  // QZSS
        // case "GL": return 6;  // GLONASS (secondary)
        case "GI": return 7;  // IRNSS/NavIC
        default: return 0;    // Unknown/Combined
    }
}

// Apply system-specific PRN offset based on uBlox NMEA 4.1 spec
export function adjustPRN(prn: number, systemId: number): number {
    switch (systemId) {
        case 1: return prn;             // GPS: no adjustment needed (1-32)
        case 2:                         // GLONASS (primary): no adjustment needed (65-96)
        case 6: return prn;             // GLONASS (secondary): no adjustment needed (65-96)
        case 3: return prn + 100;       // Galileo: add 100 (101-136)
        case 4: return prn + 200;       // BeiDou: add 200 (201-235)
        case 5: return prn;             // QZSS: no adjustment needed (193-197)
        case 7: return prn + 400;       // IRNSS/NavIC: add 400 (401-414)
        default: return prn;            // Unknown: no adjustment
    }
}

// Validate PRN is in correct range for system according to uBlox NMEA 4.1
export function validatePRN(prn: number, systemId: number): boolean {
    switch (systemId) {
        case 1: return prn >= 1 && prn <= 32;         // GPS
        case 2:                                       // GLONASS (primary)
        case 6: return prn >= 65 && prn <= 96;        // GLONASS (secondary)
        case 3: return prn >= 101 && prn <= 136;      // Galileo
        case 4: return prn >= 201 && prn <= 235;      // BeiDou
        case 5: return prn >= 193 && prn <= 197;      // QZSS
        case 7: return prn >= 401 && prn <= 414;      // IRNSS/NavIC
        default: return true;                         // Unknown: accept any
    }
}

// Get the name of the GNSS system for a given system ID
export function getSystemName(systemId: number): string {
    switch (systemId) {
        case 1: return "GPS";
        case 2:
        case 6: return "GLONASS";
        case 3: return "Galileo";
        case 4: return "BeiDou";
        case 5: return "QZSS";
        case 7: return "IRNSS/NavIC";
        default: return "Unknown";
    }
}