Since I've Googled and not found what I want to know, I thought there
might be people here who know how surveyors' instruments work.
The reason I am asking is that three different surveyors have surveyed
the same boundary peg (and others) and put the peg in three different
places, by up to 500mm away.
They have all used the same Council survey mark in the footpath
While I would have thought that a GPS unit would do the job very
easily, the surveyors did not use a GPS unit, except maybe to get the
position of North (an assumption by me). My cheap GPS unit locates the
pegs to within a metre.
They all used a device (probably with a laser) on a tripod, and a rod
with a mirror on top. I'm actually not interested in discussing any
other kind of equipment. I want to know how three surveyors could get
different results in the last few years using equipment that they say
is accurate to within a millimeter. The Council survey mark has not
moved and there have been no landslips and nobody has moved the pegs.
The pegs are next to trees and structures that have not moved.
The process for a survey appears to be:
1. find a spot across the road that is visible from the section being
2. put a peg there, put the laser above it and the mirror above the
survey mark and measure the angle and distance and declination.
Somehow the equipment knows where North is - I hope it's not using a
3. find a spot inside the section being surveyed that is visible from
where the boundary pegs are guessed to be. Put the laser there and
measure to the mirror on the spot in 2 above.
4. Put the mirror above each peg position. At the laser, key in the
distance and angle where the peg should be, and move the mirror up and
until the peg position is deemed to be correct by the equipment. This
process takes seconds only and requires no calculations by the
operator. The raising and lowering of the mirror is allowed for by the
equipment by some magic unknown process (obviously that changes the
distance, if the laser is a different altitude from the mirror). The
mirror needs to be raised above vegetation in the vicinity.
The mirror has a small bubble level on it so can be made vertical.
All around me people are putting up buildings and fences, and we need
to know where the boundaries are. My neighbour's fence is reinforced
concrete blocks and will never be moved again I'd say.
I can't measure most of the peg positions accurately with a tape
measure because the land has a slope of up to 60 degrees and is
covered in trees.
Now surveyors are highly paid professionals who in theory know what
they are doing. How come they don't agree where boundary pegs should
- posted 9 years ago