Nanometrics Data Formats Reference Guide

Chapter 1: NMXP Data Format
9 Trident
10 Janus
11-31 Reserved for future use
1.4 Compressed data packet
A data packet always consists of a timestamp header followed by n data bundles (where
n is user defined). A timestamp bundle contains a sequence number, the time of the first
sample, instrument ID (model and serial number), sample rate of packet and channel
number, and the first sample.
1.4.1 Compressed data packet header
1 byte Packet type = 1 (bit 5 = 1 indicates the packet is being retransmitted)
4 bytes Long seconds
2 bytes Sub-seconds in 10,000th of a second
2 bytes Instrument ID [bits 0-10 serial number, bits 11-15 model type]
4 bytes Sequence Number
1 byte Sample Rate, Channel # [bits 0-2 channel number, bits 3-7 sample rate]
3 bytes X0 (first sample) as a 24-bit signed integer (LSB first)
The instrument ID defines the instrument type transmitting the channel of data. Supported
types are defined in section 1.3.
The sample rate is an enumerated value:
0 reserved 10 125 s/s
1 1 s/s 11 200 s/s
2 2 s/s 12 250 s/s
3 5 s/s 13 500 s/s
4 10 s/s 14 1000 s/s
5 20 s/s 15 25 s/s
6 40 s/s 16 120 s/s
7 50 s/s 17 240 s/s
8 80 s/s 18 480 s/s
9 100 s/s 19-31 Reserved for future use
1.4.1.1 Extended seismic data header
If the first data bundle has 0 in the compression byte, indicating that all four compressed
data fields are not used, the bundle is an extended seismic data header.
1 byte extended header = 0
4 bytes XO (first sample, 32 bit version of the same field in main header)
1 byte status
bit 0 channel 1 calibration in progress
bit 1 channel 2 calibration in progress
bit 2 channel 3 calibration in progress
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Nanometrics Data Formats
2003-11-07 Reference Guide
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