Class PayloadBits

constructor

• new PayloadBits(payload: Uint8Array): PayloadBits

  Parameters

  • payload: Uint8Array

  Returns PayloadBits

bits

bitsToNumber

• bitsToNumber(bits: Bit[]): number

  Convert an array of bits (0s and 1s) to an unsigned integer ([1, 0, 1] => 5).

  Parameters

  • bits: Bit[]

    The array of bits to convert.

  Returns number

  The converted integer.

decode

• decode(payload: Uint8Array): void

  Converts AIS "armored ASCII" payload into a flat array of bits. See AIVDM/AIVDO Payload Armoring in the guide for details.

  The data payload is an ASCII-encoded bit vector. Each character represents six bits of data using two ASCII ranges: 6-bit 0-39 → ASCII 48-87 ('0' to 'W') 6-bit 40-63 → ASCII 96-119 ('`' to 'w')

  The gap ASCII 88-95 ('X' to '_') is unused.

  Parameters

  • payload: Uint8Array

    The payload to decode.

  Returns void

getBool

• getBool(start: number): boolean

  Extract a boolean (single bit) from the bit array.

  Parameters

  • start: number

    The starting position in the bit array.

  Returns boolean

  The extracted boolean.

getInt

• getInt(start: number, length: number, signed?: boolean): number

  Extract an integer (signed or unsigned) from the bit array.

  • For unsigned integers, the bits are converted directly to a number.
  • For signed integers, the first bit (MSB) indicates the sign: 0 = positive → convert bits to number as-is 1 = negative → use two's complement to get the negative value

  Parameters

  • start: number

    The starting position in the bit array.

  • length: number

    The number of bits to extract.

  • Optionalsigned: boolean

    Whether the integer is signed.

  Returns number

  The extracted integer.

getLat

• getLat(start: number): number

  Parameters

  • start: number

  Returns number

getLength

• getLength(): number

  Returns number

getLon

• getLon(start: number): number

  Parameters

  • start: number

  Returns number

getStr

• getStr(start: number, length?: number): string

  Extract a text string from the bit array.

  Parameters

  • start: number

    The starting position in the bit array.

  • Optionallength: number

    The number of bits to extract - if not provided, extracts to end of array.

  Returns string

  The extracted text string.