Observing a stable environment
You won’t believe me when I say that being asked to monitor a stable environment is sometimes harder than monitoring an environment on the move and changing with time/works.
Establishing and maintaining a stable control network is the first challenge. How do we ever know our control network is going to be 100% stable? Well, apart from experience, we probably don’t. So how thorough does a stable network need to be? This depends on the environment, structures and tolerances to be monitored. On a specific site a while ago we had a pylon lifting and dropping by up to 100mm, no problem in the given environment and conditions but this wouldn’t be acceptable in a chemical plant or on a property etc.
So the phone call came, can we observe and monitor the movement of crane rails in the process of production still to less than 0.5mm in level? I couldn’t guarantee it but I knew if we couldn’t do it, there wouldn’t be many surveyors who can. Quoting tolerances on the equipment to be used (Leica DNA03 level) helped. Experience was my biggest guide. Observing and monitoring structures and land across the country for over 14 years was the basis of my confidence.
Returning to sites after periods of weeks and observing/calculating points to less than 0.2mm frequently was all I needed to know we could deliver, so long as the rails weren’t moving. If they were or the survey environment wasn’t in our favour, I knew we’d struggle with any confidence.
So off we trot, equipment and experience in hand. Two surveys conducted in the space of a single day. The largest difference we got in those two surveys on over 50 points surveyed? 0.2mm. Delivered. Trust your experience but be prepared for your environment or factors outside your control to have an impact.