To facilitate the design a high precision topographic survey of the motorway and interchanges were required up to and including the highway boundary.
The survey area covered approximately 50 Km of carriageway and 7 motorway junctions. Road levels were to be surveyed to 5mm accuracy with the proviso that ‘live lane’ closures on the M50 were not permitted for cost and safety reasons.
As a result of this restriction SACYR awarded the contract to Longdin and Browning who used their innovative patented Clear Cone system to survey live carriageways from the hardshoulder.
The system solved the problem of closing ‘live lanes’ by placing the surveyor within a survey vehicle and therefore increasing safety and reducing traffic management costs.
The Clear Cone system uses reflectorless survey equipment located in a survey vehicle situated on the hardshoulder under traffic management regulations. In this case a hardshoulder closure of 1500m was needed.
Two Clear Cone survey crews were used on the M50. They surveyed 1500m per day with 3 additional land crews surveying the junctions using reflectorless survey equipment. The highway boundary was surveyed using GPS in RTK mode and establishing control using GPS equipment. With the combination of these various survey techniques Longdin and Browning were able to complete the survey in a cost effective and safe way.