Response 57h, RAWDATA (Position or real-time survey data report)

Report Packet 57h is sent in response to Command 56h GETRAW. These packets will also be streamed if RT17/RT27 is enabled as a streamed output, either via the RT17/RT27 or using the 64h APPFILE command.

The raw satellite data responses are likely to span more than one RAWDATA reply. To overcome this, page information and an epoch counter are supplied as an extended framing. The first and subsequent RAWDATA record pages will be filled with a maximum of 248 bytes consisting of 4 bytes of page and flag information and 244 bytes of raw satellite data. The raw satellite data will be split where ever the 244 byte boundary falls, regardless of internal variable boundaries. Therefore the external device receiving the multiple pages must reconstruct the raw satellite record using the 244 byte pages before parsing the data.

The terms RT17 and RT27 are related to a data logging encapsulation, and may unfortunately cause some confusion when trying to understand the 57h response. In summary:

  • RT17 is GPS-only

    This outputs 57h DATA RECORD subtype 0 for SV measurement data (record type 17) and/or 57h DATA RECORD subtype 1 for position data (record type 11). The position solution will use any and all GNSS satellite; however, it will only list GPS satellites used.

  • RT27 is all GNSS

    This outputs 57h DATA RECORD subtype 6 for SV measurement data (record type 27) and/or 57h DATA RECORD subtype 7 for position data (record type 29).

All data in the packet flows from the receiver to the data collector.

Byte

Item

Type

Value

Meaning

0

STX

1 (Char)

02h

Start Transmission

1

STATUS

1 (Char)

??h

Receiver Status Code

2

PACKET TYPE

1 (Char)

57h

Response Packet Type

3

LENGTH

1 (Char)

??h

Bytes of data

----- RESPONSE HEADER -----

4

Record Type

1 (byte)

00h, 01h, 02h, 06h, and 07h

Record Type indicates which raw data record type is being sent:

  • 0: Real-time GPS survey data (RT-17)
  • 1: Position Record (RT-11)
  • 2: Event Mark
  • 6: Real-time GNSS Survey Data (type 27)
  • 7: Enhanced Position Record (type 29)

5

Page Number

1 (byte)

 

Page Counter indicates how many pages there are for this epoch and what this page number is (for example, 1 of 3, 2 of 3, 3 of 3).

This byte is split into two sections of 4 bits allowing for 15 pages where:

bits 0–3: Page total

bits 4–7: Current page number

So, for example, 0x23 would indicate the second page out of three.

6

Reply Number

1 (byte)

00h–FFh

Reply Number is a 0–255 rollover counter, which is incremented with every reply but remains constant across pages within one reply. This value should be checked on second and subsequent pages to ensure that pages of the same reply are recombined rather than those from different reply.

7

Record Interpretation Flags

1 (byte)

RECORD INTERPRETATION FLAGS indicates special attributes of the record that must be used in parsing values. Defined values are:

  • bit 0 set : Concise format

  • bit 1 set : Enhanced Record with real-time flags and IODE information

  • bit 2 and bit 3: The number of extra 15-page sets

    • bit [3,2] = [0,0] indicates <= 15 pages

    • bit [3,2] = [0,1] indicates <= 30 pages but > 15 pages

    • bit [3,2] = [1,0] indicates <= 45 pages but > 30 pages

    • bit [3,2] = [1,1] indicates <= 60 pages but > 45 pages

  • bits 4–7 reserved

----- DATA RECORDS – Subtype 0, 1, 2, 6, or 7 -----

Data from one of the records that are encoded in type 57h records, as indicated by byte #4 RECORD TYPE. An individual record may extend over several RAWDATA packets. See:

Last byte of data + 1

CHECKSUM

Char

??h. See Data collector format: packet structure.

Checksum Value

Last byte of data + 2

ETX

Char

03h

End Transmission