Reflections on Independently Completing a Topographic Survey
A topographic survey was conducted to provide comprehensive terrain model before the subdivision of residential land. Compared to my first independent survey, my proficiency and work efficiency had significantly improved. However, there were still some issues: first, the lines on the computer screen appeared crossed, whereas this problem did not occur on the TSC7 screen; second, I missed surveying some terrain features. These issues highlighted my lack of skill and experience in surveying. To ensure data accuracy, I braved the wind and snow to re-survey the next day. In the end, David confirmed and used the data I had independently collected, which greatly encouraged me.
I have learned lots of measurement techniques in my short time with Definition Surveying so far. One task was the measurement of the height of the sewage pipeline invert level, which may seem like a very simple task, but it contains several points worth noting.
Firstly, there is specialised equipment for opening manhole covers and techniques to do it safely. There are different types of manholes covers, sometimes they are circular and sometimes rectangle in shape. Some devices for opening manhole covers cannot be used universally which makes it tricky to open in some cases.
Secondly, due to the thick and heavy manhole cover, it is difficult for one person to lift it up; when two people cooperate to open the manhole cover it can be done. Extra attention should also be paid to the rectangle manhole covers as they are prone to falling in. If it falls, it's a tragedy as you can’t enter the manhole due to the potential fumes. I haven't encountered such trouble, and I will continue to be careful to make sure it doesn’t happen.
The third issue is that when measuring height, the measurement point is not perpendicular to the position of the manhole cover on the same line. There are a few methods that can be used to get the correct invert height. The best method is to utilise the tilt sensor on the GNSS receiver. At Definition Surveying we use the Trimble R12i. This gives us an accurate position at the point at the bottom of the pole. A ruler and a laser device can also be used to compare and check the height. A tape measure is also used to get another check on the depth from lid level to the invert level.
This experience made me realise more deeply that as a surveyor, one must have a clear goal in mind and persevere despite challenges. I am grateful for David’s guidance and help, which has given me more experience as a Survey Technician.