1. Site survey and co-location
Sten Bergstrand
July 2017
SAFETY AND TRANSPORT MEASUREMENT SCIENCE AND TECHNOLOGY

2. Introduction
Local ties are geometric vectors measured between reference points of different stations, including the full covariance information in both temporal and spatial domain
Definitions are important to convey information
Following Paris workshop
Resolution between services available at IERS URL: rvey/Bergstrand_etal_REFAG2014_TieResolution.pdf (not REFAG proceedings…)
Rotation of surveying results into ITRF via GNSS currently destroys any survey…

3. Every station has one geometric reference point
Stations have DOMES numbers
Reference points are geometrically determined points on the stations
The definitions of these points are determined by the services
The term ”reference point” needs to be used exclusively for this geometrically determined point

4. One geometric reference point
Example of internet search result for ”gnss antenna reference point” –
not recommended for clarity…
Other relations, e.g.
- PCO
- PCV
- pointing
- internal geometries - time delays
- systematic errors
- deformation
- etc…
are part of the service obligation
(with aid from surveyors, where applicable)

5. Every site should be represented by a physical marker.
Invariant to station changes
Permanent
Preferably attached to bedrock

6. Exemplified by DORIS antenna
Courtesy: Saunier et al.

7. VLBI
Automatic schedule-generated terrestrial monitoring system developed, applied e.g. at CONT14 (Lösler et al.)
GNSS antennas mounted on telescopes

8. How to incorporate local ties and uncertainties in next ITRF?
Plans, gateways, commitments, timings? Recommendations are already available since many years.
Surveying techniques should generally perform better than current discrepancies between analytic site solutions
Quality or quantity?
Focus on any separate technique?
More surveys? If so: who and how?

9. General Ishikawa diagram?
Reference point
Ref. point to rec. unit
Local network
Geometry
Deformation
n points
GNSS
Temperature
Geometry
Accessibility
Arcs
Constraints
Size
Cables
Rec.unit
Definition
Ground stability
n measurements
Elevation dependence
Orientation of vertical
Points
Variation
Frequency
Observations
Cut-offs
Operator
Play
Repeatability
Solar radiation
Traceability
Interval
Temperature
Pressure
Temperature
Length
Longevity
Stability
Met.sensor height
Monument
Temporal evolution
Instrument calibration

10. Thankyou – Please provide input!
Sten Bergstrand
SAFETY AND TRANSPORT MEASUREMENT SCIENCE AND TECHNOLOGY