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

[Les Williams]

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
>>
>