Subject: [IGSSTATION-3429]: ZIM2 and ZIMM heavy snow effects Nov. 30 - Dec. 2, 2009: Do not use data
From: Brockmann Elmar LT <[email-masked]>
To: "[email-masked]'" <[email-masked]>, "[email-masked]'" <[email-masked]>
Date: Thu, 3 Dec 2009 08:47:22 +0100

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IGS Station Mail          02 Dec 23:47:28 PST 2009      Message Number 3429
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Author: E. Brockmann

Dear colleagues,

After the heavy snow falls from Nov. 30, 2009 (DOY 334) the two chokering antennas for the ZIMM and ZIM2 station were completely covered with (extreme wet) snow. This, together
with a very asymmetrical melting caused quite bad coordinate results when analyzing the data.

From our hourly monitoring solutions we found "excursions" of the coordinates of upto 8 cm vertically and upto 2-3 cm horizontally (peak at DOY 334.75).
A constant remaining effect of 4 cm vertically and 2 cm horizontally forced us to clean the antenna.

Pictures, taken shortly before cleaning the antennas at Dec. 2, 2009 (15:30 UT, DOY 336) may give an impression of the situation
(http://www.swisstopo.admin.ch/swisstopo/geodesy/pnac/divers/pictures/2009_12_02_zimm_snow.jpg
http://www.swisstopo.admin.ch/swisstopo/geodesy/pnac/divers/pictures/2009_12_02_zim2_snow.jpg).

We recommend to exclude the data of the two stations ZIM2 and ZIMM between DOY 334 and 336 (Nov. 30 - Dec. 2 2009) from high precision GNSS applications.

Sorry for the inconveniences this problems may have caused.

Best Regards.
Elmar Brockmann

Elmar Brockmann
swisstopo
Federal Office of Topography
Geodesy
Seftigenstrasse 264
CH-3084 Wabern
Phone   +41 31 963 21 11        operator
        +41 31 963 22 56        direct
Fax     +41 31 963 24 59
[email-masked]
www.swisstopo.ch