Measurements for Route Surveys
I work for a heavy haul company and we move very large items from point a to point b and in between we need to know what we’re going to come across, so we send someone on the proposed route, look at the corners and put a high pole on the truck to see if we can roll under an obstacle. For most moves that works, but the one I’m currently working on is quite challenging and I find myself needing far more accurate measurements, but I also need to do them in traffic. As professionals you guys play in traffic from time to time, what I’m looking for is some equipment to help me get in the 10cm range of accuracy for horizontal measurements and 2cm accuracy for vertical clearances. I want to be able to plot out a basic layout of corners and bridges without getting too involved. Is there equipment a non-surveyor can use to do this safely and accurately in a quick manner? On some jobs the requirements are for full blown surveys, and that where we bring in the big guns and hire pros, but for the most part I run 200 to 400 miles a day doing route surveys and look at between 10 to 30 corners/bridges/signs in that same day. Hiring a pro for a route from Houston to Reno is just not going to happen. It would be a waste of a professionals talent and the shipper/clients money.
TxDOT should be able to give you a route across Texas and hopefully DOT in the other states will pick up after that.
All that information is in their system and they know the height of everything along their systems.
Of course that can change due to changeouts and elemental effects to the overheads since their information was collected.
The basic way I learned to find the height of something was to use a transit and level the scope which should be at 0 degrees or 90 degrees on your instrument(depending upon if it is a zenith or vertical angle) and sight a rod to record the height at a point under the line and then get the distance to the rod (today we would use a totalstation) then move the scope to sight the overhead object and record that angle and use a trig function to obtain that vertical height and add the two together for the height above the surface at that height.
Of course many other things can affect your loads ability to pass safely. Length of your rig and the placement of the highest point of your cargo and the slope and perhaps vertical curve that may be at that point which is the case of many overhead crossings.
The Interstate highway system usually have those problems when passing thru major cities.
I have seen loads that had totake the exit to get around overhead bridges that could not be passed and the route would take up and over the crossing roadway where the overheads had been designed to be well above that of the overhead bridge.
Many times I have seen a crew that used boards attached to loads to allow the overhead lines to be lifted and slid over the rig and its load and mostly for moving houses.
I have also seen crews working ahead of extra high loads that worked with the local overhead agencies to manually lift the power lines for safe passage.
Do not hesitate to contact DOT offices, they have an expert that keeps up with creating routes for these purposes.
I agree the motor carrier database does contain all the bridge clearances and the load/weight for bridge loads. I have provided lots of bridge clearance measurements.