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RAKW GNSS time series- vertical component degradation #83

Closed elidana closed 10 months ago

elidana commented 2 years ago

The GNSS site RAKW is showing a degradation of time series data after 22 April 2021 (Sigrun picked this up and notified us).

Do you know what happened to RAKW around the 22 April this year? Data look at bit messy and there is a 5 cm subsidence at the site. Looks like something happened to the antenna. I suspect the antenna is broken and would need the quality plot data to check that

@megankortink confirmed that there are no equipment change that can explain that or issues with the site recorded in the ticketing system, and that the antenna at the site is +10years old.

It could be the antenna it looks quite old …. Trimble Navigation Ltd.,TRM57971.00,1441031099,RAKW,0.002,0,0,0,2011-02-16T04:05:01Z,9999-01-01T00:00:00Z

Land ownership changed around the same period, so we will investigate if the vertical offset and poor quality of data after April 22 might have been caused by a change in the antenna surroundings. Another possible options is that the antenna is degrading, as it was installed in 2011

A link to the vertical time series plot: https://fits.geonet.org.nz/plot?type=scatter&sites=RAKW&typeID=u&start=2020-01-01T00:00:00Z&days=700

meganmadley commented 2 years ago

Some basic plots for cycleslip and mp1/mp2 from the 1st April 2021 until 1st June 2021, initial testing, can test with a longer duration image image

Mp1 (0.21 --> 0.25) and Mp2 (0.48 --> 0.54) looks like values are slowly increasing, cycle slip fairly consistant and fluctuating

meganmadley commented 2 years ago

Data for Mp1, Mp2, Cycleslip from gloria @elidana

RAKW_mp1_mp2 Drop in mp2 in September 2019 likely related to netr9 being swapped to an alloy (https://github.com/GeoNet/tickets/issues/5232)

RAKWcycleslip

elidana commented 2 years ago

We have removed the antenna and installed a new one today. No water damage was found in either antenna cable ends, or the TRM57971.00 that was installed at the site. We have also performed a tie in survey to have a better control on the offset introduced by the antenna swap.

Will revisit time series data in 2 weeks time to (hopefully) verify an improvement in data quality

elidana commented 2 years ago

The RAWK time series has already improved, with the apparent offset on the vertical component is now reverted and noise now back to standard data scattering.

Horizontal components might also have been affected, and it does look like the antenna might have cracked and water then seeped in to it, but there are no visible cracks in the antenna, apart the normal build up of gren scum etc. no obvious cracking or external damage

period with bad data is from 2021-04-22 to 2021-10-20 (UTC), that was when the antenna was swapped.