AMBIENT TEMPERATURE CHANGES AND THE IMPACT TO

TIME MEASUREMENT ERROR

Vukan Ogrizović, Jelena Gučević, Siniša Delčev

University of BelgradeFaculty of Civil EngineeringDepartment of Geodesy and Geoinformatics

Vertical deflections

Natural coordinates ()- astronomical -

Elipsoidal coordinates ()- geodetic -

const.1

const. s

const.3

const.4

const.5

const.1

const.s

const.3

const.4

const.5

sin

cos

A

Measuring systems for() determination

TZK2 - D(Institut für Erdmessung,

Hannover)

DIADEM(Eidgenössishe Technische

Hochschule, Zürich)

Time-keeping in field

• 1PPS from GPS to DB9 via RS232• GPST to quartz oscillator ticks• RTOS

Frequency vs temperature plots

• Variations in temperature -> major influence on the crystal frequency

• Changing the curvature of a crystal cut can make the slope less steep

Experiment set-up

• Time reference: Trimble NetRS w Zephyr Geodetic• UTC source: 1PPS output (BNC type) wired to DB9• SI second acquisition: Interrupt handler under RTOS• Resolution:

s MHz 9107133

Set-up #1

Raw data

After removing the blunders

- Testing performed outdoors- Ambient temperature: ~17°C- Measuring session: ~2 h

Set-up #2

Raw data

After removing the blunders

- Testing at different environmental conditions - Ambient temperature increased from 0°C to 21°C- Measuring session: ~5 h

Set-up 2a Set-up 2bSet-up 2c

Calculation of the clock model

• Four tests, each cca 2 h long:– #1: T = 17°C– #2a: T = 0°C– #2b: T = 21°C– #2c: 0°C < T < 21°C

• Clock drift & bias according to the linear model:

ii ThTUTC 10

Calculated biases (tab'd)Set-up # T [ °C] h [s/h] sh [s/h]

1 16 0,003 0,001

2a 0 -0,033 0,002

2b 20 0,006 0,002

2c 0-21 -0,026 0,003

Calculated biases (graph)

Conclusion and remarks

• Clock bias strogly dependent on temperature• Need for stable environmental conditions• Shorter session -> linear clock model

Thank you for your attention!

University of BelgradeFaculty of Civil EngineeringDepartment of Geodesy and Geoinformatics

Vukan Ogrizović, vukan@grf.bg.ac.rsJelena Gučević, jgucevic@grf.bg.ac.rsSiniša Delčev, delcev@grf.bg.ac.rs