Data 81 (Mini Location)

The mini location information, only provides 6 parts information of fix state, fix mode, longitude, latitude, UTC time and speed.

The frame format of the Data 81 unit is as follows:

For example (Total 17 bytes):
51 0F 09 07 3C 46 FF 01 DB 88 57 5F 17 9D A0 01 7D

Parts

Fields

Length (Byte)

Range/Format

Default

ID

Data ID

1

51H (81)

51H (81)

Length

Data Length

1

00H or 0FH

Content

Fix State & Fix Mode

1

Longitude

4

Latitude

4

UTC Time

4

Speed

2

0000H-FFFFH (*0.1 km/h)

  • Fix State & Fix Mode

    The upper 4 bits (bit7 to bit4) represent satellites signal strength level, the next 2 bits (bit3 to bit2) represent the fix state, and the lowest 2 bits (bit1 to bit0) represent the fix mode. Details are as follows.

    • Signal Strength Level (Bit7 to Bit4)

      Indicates the signal strength level of the satellites in use.

      • 0b0000 - Unknown.

      • 0b0001 - Great.

      • 0b0010 - Good.

      • 0b0011 - Normal.

      • 0b0100 - Weak.

      Typical values are as follows:

      Value

      Signal Strength (C/N0)

      Level

      0

      Unknown

      Unknown

      1

      C/N0 >= 40

      Great

      2

      33 <= C/N0 < 40

      Good

      3

      28 <= C/N0 < 33

      Normal

      4

      C/N0 < 28

      Weak

    • Fix State (Bit3 to Bit2)

      Indicates the current positioning status of the GNSS chip.

      • 0b00 - Off. GNSS is not working at the moment. In this case, the ‘longitude’, ‘latitude’, ‘speed’, ‘UTC time’ etc. are the same as the last valid positioning.

      • 0b01 - No fix. GNSS worked but could not get the position. In this case, the ‘longitude’, ‘latitude’, ‘speed’, ‘UTC time’ etc. are the same as the last valid positioning.

      • 0b10 - Fix. GNSS worked and got the accurate location. The values of all fields are reliable to use.

    • Fix Mode (Bit1 to Bit0)

      Indicates in which positioning mode the following position information (longitude, latitude, etc.) was obtained.

      • 0b00 - 2D GNSS fix.

      • 0b01 - 3D GNSS fix.

      • 0b11 - Unknown.

  • Longitude

    The longitude is converted to an integer with 6 implicit decimals and this integer is reported in HEX format; if its value is negative, it is represented in 2’s complement format. For the converted longitude, a positive number indicates the east longitude and a negative number indicates the west longitude.

    For example, 073C46FFH (i.e., 121390847) means longitude 121.390847 degrees, and F920A8E1H (i.e., -115300127) means longitude -115.300127 degrees.

  • Latitude

    The latitude is converted to an integer with 6 implicit decimals and this integer is reported in HEX format; if its value is negative, it is represented in 2’s complement format. For the converted latitude, a positive number indicates the north latitude and a negative number indicates the south latitude.

    For example, 01DB8857H (i.e., 31164503) means latitude 31.164503 degrees, and FF2DC096H (i.e., -13778794) means latitude -13.778794 degrees.

  • UTC Time

    The UTC time obtained from the GNSS chip, difference, in seconds, between the current time and midnight, January 1, 1970.

    For example, 5DD52EFAH (i.e., 1574252282) means November 20, 2019, 20:18:02.

  • Speed

    The speed is obtained from the GNSS chip. Speed over ground, expressed as a 16-bit unsigned integer and the unit is 0.1 km/h.

    For example, 017DH (i.e., 381) means speed 38.1 km/h.