BIRD IQC5000B - Page 79

Post Processing IQC5000 Recorded Data
68
Example xmrk XML File
<?xml version="1.0" encoding="utf-8"?>
<xcom_markers>
<marker marker_number="0" absolut
e_sample_number="81390" timestamp="2014:013:19:55:41.635163"
timestamp_source="IRIG" latitude="38°56.9636'" latitude_direction="N" longitude="077°22.2888'"
longitude_direction="W" altitude="00120" speed="000.0" event_code="marker1_rising"/>
<marker marker_number="1" absolut
e_sample_number="181388" timestamp="2014:013:19:55:41.637163"
timestamp_source="IRIG" latitude="38°56.9636'" latitude_direction="N" longitude="077°22.2888'"
longitude_direction="W" altitude="00120" speed="000.0" event_code="marker1_rising"/>
<marker marker_number="2" absolut
e_sample_number="281390" timestamp="2014:013:19:55:41.639162"
timestamp_source="IRIG" latitude="38°56.9636'" latitude_direction="N" longitude="077°22.2888'"
longitude_direction="W" altitude="00120" speed="000.0" event_code="marker1_rising"/>
<marker marker_number="3" absolut
e_sample_number="381392" timestamp="2014:013:19:55:41.641156"
timestamp_source="IRIG" latitude="38°56.9636'" latitude_direction="N" longitude="077°22.2888'"
longitude_direction="W" altitude="00120" speed="000.0" event_code="marker1_rising"/>
</xcom_markers>
The preceding example XML marker
file has 4 markers, beginning at marker_number 0 and ending at
marker_number 3.
A marker was produced roughly every 2 ms, as illustrated by the dif
ferences in the timestamps. (Dividing the
difference in absolute_sample_number by the sample_rate located in the header file will also equal delta time.)
The presence of location data (latitude, latitude_direction, longitude,
longitude_direction, altitude, and speed)
indicates that a GPS device was connected.
The timestamp_source indicates that an IRIG device was used in a
ddition to GPS. Due to its higher precision, IRIG
time is used over NMEA time when both are present.
The recording was made while stationary, illustrated by the spee
d remaining at 0 and the latitude/longitude never
changing.
The event_code values show a pattern of markers with the rising e
dge of marker 1 followed by the falling edge of
marker 1. This coupled with the regular delta between timestamps of 2ms suggests that a 250Hz 50% duty cycle
square wave was used to stimulate markers.