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GPS Plotting
Recently we tracked a 2500mm wide by 1500mm high culvert 350 meters
along the Newtown area in the Market theatre area below the Highway.
We used the Trimble hand held instrument to locate GPS co-ordinates
as well as Rigid pipe location technologies, cameras could not
access these culverts as the storm water culverts run in cascading
500mm drops – these vertical drops damage the cameras as well as
make it impossible for the crawlers to climb them.
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Saturday morning 8. am we began locating the main culvert
starting from the man hole that is visible from above ground.
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We
plotted this one on GPS for you as per plan
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DIFFERENTIAL CORRECTIONS ARE Accurate WITHIN 150-300mm when we
use a staff it is down to 100mm accuracy
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The
GEO XH 2008 Geo Explorer Trimble Hand Held Sub Foot GPS was used
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We
tracked using the Nav star Constellation American Satellites –
Not the (Glo NASS) Russian
We
started inspecting from point one as per drawing supplied
Our camera (crawler) reached the first 35 meters when we found rocks
and debris that we removed to get passed to do the inspection as the
camera could not pass these, after removing them we continued 50
meters and hit a vertical waterfall showering down from above – when
we zoomed and panned we saw a cascading wall in front of us, No
camera inspection can be done as cameras cant crawl up vertical
walls 500mm high, The culvert is on a cascading layered design that
drops 500mm at points of between 50-80mtrs. We
withdrew the camera from this side of the culvert and drove around
to the top to try insert the camera up stream near CARR road
entrance. After 60 minutes of searching we could not locate any
manholes to insert the camera in on the property in the CARR street
side. We returned back to our starting point. We
used the crawler with a harness and inserted a sonde with a push rod
system with a transmitter on the head as per photo. Then we manually
walked in the sewer until it was too dangerous as oxygen levels were
too low so we exited, We located the intersection of the other large
culvert and marked this above ground. We also pushed a further 80 mtrs down
What we propose to do next is excavate through the tarred surface at
the point of intersection as we can insert the camera from this
point and we don’t need breathing apparatus for humans to enter the
culvert. The
sewer below is blocked causing effluent from the sewer to overflow
from below and run into the storm water culvert, this methane is
what impairs our breathing. We
changed over to sonde location together with transmission of an 8khz
signal down the line We
did record our starting inverts and will continue with inverts once
we have excavated to get through the next manhole, please advise if
you want us to plot the rest of the culvert or if we must put our
efforts into other specific lines required by your client, The
jpg folder called “Last point recorde 679 kb” is a picture of three
black spray paint marks we made – the middle mark is the furthest
point we achieved in the culvert and the mark on the curb is the
point of intersection of the other culvert as it enters the main
one. |
