Carlson Software Forum

Posted: **Thu Jan 04, 2007 5:29 am**

Should we have C & R turned on in SurvCE if it is already applied in a
Topcon GPT 3003 total station? This has been discussed on the rpls.com
board, but there were varying opinions.

According to the SurvCE manual, "It is recommended that this factor be
set On, except in those very rare cases where the instrument factors in
curvature and refraction."

Is the Topcon one of those "rare" cases, or am I "double correcting" the
data. I would like to get this settled, at least in my mind, from
someone that knows for sure, once and for all.
thanks,
terry

Posted: **Tue Jan 16, 2007 10:39 pm**

Well, looks like no one is going to bite on this one.
According to my instrument dealer service department, if C&R is turned
on in the instrument, it should be off in the data collector, else the
'double correction' is applied.
If anyone else has a different opinion or reasoning on this, or a
confirmation, please speak up.
thanks.

Terry Strickland wrote:

Should we have C & R turned on in SurvCE if it is already applied in a
Topcon GPT 3003 total station? This has been discussed on the rpls.com
board, but there were varying opinions.

According to the SurvCE manual, "It is recommended that this factor be
set On, except in those very rare cases where the instrument factors in
curvature and refraction."

Is the Topcon one of those "rare" cases, or am I "double correcting" the
data. I would like to get this settled, at least in my mind, from
someone that knows for sure, once and for all.
thanks,
terry

Posted: **Wed Jan 17, 2007 3:27 am**

That is our understanding as well. You must either be taking some long
shots or doing high precision leveling for the C & R correction to be
significant though. According to Wolf & Brinker, the combined effect in
height measurement over a 300 foot sight is 0.0019 feet.
We set it in the instrument and leave it off in the data collector.

-Jay

"Terry Strickland" <jtstrickland@bellsouth.net> wrote in message
news:eoj2jd$i0b$1@update.carlsonsw.com...

Well, looks like no one is going to bite on this one.
According to my instrument dealer service department, if C&R is turned on
in the instrument, it should be off in the data collector, else the
'double correction' is applied.
If anyone else has a different opinion or reasoning on this, or a
confirmation, please speak up.
thanks.

Terry Strickland wrote:
Should we have C & R turned on in SurvCE if it is already applied in a
Topcon GPT 3003 total station? This has been discussed on the rpls.com
board, but there were varying opinions.

According to the SurvCE manual, "It is recommended that this factor be
set On, except in those very rare cases where the instrument factors in
curvature and refraction."

Is the Topcon one of those "rare" cases, or am I "double correcting" the
data. I would like to get this settled, at least in my mind, from someone
that knows for sure, once and for all.
thanks,
terry

Posted: **Wed Jan 17, 2007 7:25 pm**

I posted this question on rpls.com. The general opinion there is that
the data is not double corrected, since the DC downloads the raw data,
and the correction would be applied to the reduced vertical distance,
and most everyone that replied said the correction could be on both in
the instrument and data collector with no adverse effects.
As you say, the difference is almost insignificant. It would be
difficult to determine using a 5 second gun, but I plan on trying a test
after it warms up a bit.
thanks,
terry

BSS wrote:

That is our understanding as well. You must either be taking some long
shots or doing high precision leveling for the C & R correction to be
significant though. According to Wolf & Brinker, the combined effect in
height measurement over a 300 foot sight is 0.0019 feet.
We set it in the instrument and leave it off in the data collector.

-Jay

"Terry Strickland" <jtstrickland@bellsouth.net> wrote in message
news:eoj2jd$i0b$1@update.carlsonsw.com...
Well, looks like no one is going to bite on this one.
According to my instrument dealer service department, if C&R is turned on
in the instrument, it should be off in the data collector, else the
'double correction' is applied.
If anyone else has a different opinion or reasoning on this, or a
confirmation, please speak up.
thanks.

Terry Strickland wrote:
Should we have C & R turned on in SurvCE if it is already applied in a
Topcon GPT 3003 total station? This has been discussed on the rpls.com
board, but there were varying opinions.

According to the SurvCE manual, "It is recommended that this factor be
set On, except in those very rare cases where the instrument factors in
curvature and refraction."

Is the Topcon one of those "rare" cases, or am I "double correcting" the
data. I would like to get this settled, at least in my mind, from someone
that knows for sure, once and for all.
thanks,
terry

Posted: **Tue Mar 13, 2007 11:25 pm**

Unless something has changed since I used Topcon's Data stream, the output
to the data collector is uncorrected. The effect is normally somewhere
around 4.25 seconds per thousand feet. That's exponential. The vertical
distance effect at 500' is 0.005'. At 3000' the vertical effect is 0.185'.
Curvature is minor but calculable. Refraction changes with the atmospheric
and light conditions. If you want to check for double correction. make sure
your test is done at a distance of at least 3k feet.

Carlson Software Forum

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Curvature & Refraction in SurvCE?

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