Durban (South Africa) Site History

History Summary

Tide Gauge Benchmark (TGBM) Description

Trig survey BM 4212 is at the east end of Salisbury Island. UTM Grid Reference 36 JUB 109930.

Benchmark relationships

• Tide Gauge Zero (TGZ) = South Africa Chart Datum
• TGZ = 0.838m below LLD (MSL) until 31 December 1978
• TGZ = 0.900m below LLD (MSL) from 01 January 1979
• TGZ = 0.904m below BM 4212

All heights have been referred to the station tide staff zero which is linked to fixed benchmarks. The original data were adjusted with leveling information provided by the contributors to the 1987 data as follows:

*Correction of shift in reference level deduced from the plot of hourly residuals, daily and monthly means, and differences with the corrected monthly means of the Permanent Service for Mean Sea Level.

There is a datum shift of -230mm after the 31st December 1987. All post 1987 data were received from the South African Hydrographic Office and reference to South Africa Chart Datum. Therefore there is a 230mm difference between these data and those previously adjusted by the TOGA Sea Level Center to the 1987 data.

Quality Assessment

Comment

The timing of the gauge appears to be off by a fraction of an hour in some instances.

Following possible datum shifts noted:

• Approximately -50cm on 26 October 1992.
• Approximately +35cm on 29 June 1993.
• Approximately -20cm on 02 September 1994.
• Approximately +20cm on 26 January 1996.

Note

Timing shifted by +2 hours 1997 142-174