Fixing a station's height only, or x,y only

[Martin Green]

As Les says surveying from the bench mark to the circle appears to be the
obvious fix.  This can be done with a plumb leg, such that any clino
corrections are not applied eg. If the bracket to the top was 80cm.

*data normal from to tape compass clino
benchmark circle 0.8 - up

Regards,
Martin

On Sun, 15 Aug 2021, 14:54 Les Williams, <les at les.williams.name> wrote:

> That is a fair point Graham, although knowing Tarquin I have to say why
> not... :P
> Surveying from the bench mark to the centre of the circle is the obvious
> fix
>
> Les
>
> On 15/08/2021 13:25, Graham Mullan wrote:
> > That fails, Les, 'cos Tarquin cannot survey an accurate leg to a point
> that's somewhere inside a lump of concrete.
> >
> > As far as I can see, the most straightforward way is to measure the
> vertical length from the benchmark to the top circle and add that to the
> height.
> >
> > Graham
> >
> > -----Original Message-----
> > From: Cave-Surveying <cave-surveying-bounces at survex.com> On Behalf Of
> Les Williams
> > Sent: 15 August 2021 12:44
> > To: cave-surveying at survex.com
> > Subject: Re: Fixing a station's height only, or x,y only
> >
> > Hi Tarquin
> > Surely the x, y and z are actually representative of the same point,
> i.e. an "imaginary point" centred inside the trig point directly below the
> centre of the circle and at an altitude of z. This point will have the same
> x and y coordinates as the circle on the top, and the same altitude as the
> bench mark on the side.
> > As such, why6 don't you just fix that imaginary point.
> >
> > Les
> >
> > On 14/08/2021 20:30, Tarquin Wilton-Jones wrote:
> >> Hi,
> >>
> >> I have a survey that starts at a trigpoint. The trigpoint has a height
> >> specified for the benchmark bracket on its side, and x,y coordinates for
> >> the circle on its top. The survey has stations on both the benchmark and
> >> the centre of the top.
> >>
> >> I need to be able to specify the x,y for the top, and the z for the
> >> bracket on the side.
> >>
> >> Can survex allow me to do this, or do I need to do all the maths myself
> >> to work out the height of the top so I can fix all three coordinate
> >> dimensions for a single point?
> >>
> >> What I want is this:
> >> *fix 2 - - 123.4
> >> *fix 4 1234.5 6789.0 -
> >>
> >> >From what I can see in the docs, none of these parameters are optional,
> >> so how can you deal with situation in survex?
> >>
> >> Cheers,
> >>
> >> Tarquin
> >>
> >
>
>
> --
> Cave-Surveying https://lists.survex.com/mailman/listinfo/cave-surveying
>
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