AG Surveys was approached by one of their regular clients to give advice in the survey methodology for a major Highway England (HE) trunk road project. The aim was to collect mobile mapping data for all HE road assets. The problem, how to control such a vast road network accurately, minimising the risk to survey personnel on site, keeping the timing down (and therefore costs), yet still achieve 10mm accuracy!
AG Surveys prepared a theoretical methodology, which was checked and discussed by the client. We were then asked to put the theory to the test and the A1 between Worksop and Stamford was chosen. Control markers were glued to bridge faces and surveyed reflectorless from the opposite site, using static GNSS setups as control into the national grid and datum systems. The surveyor was only 1minute on average near the carriageway (still off the hardshoulder) and all other work could be done from the overbridge or upper embankments. Detailed checks confirmed the accuracy of the methodology and the predicted timing of the project was kept to the hour.
Once the test survey and methodology was confirmed to be acceptable, we had the next email from our client asking us to do the whole northern half of England! After the shock had settled, a masterplan was developed and signed off by the client for over 550 control markers to be placed at 10km or less spacing on all HE trunkroads in the northern half of England. We calculated that the project would take 3 teams of 2 staff over 10 weeks, as all GNSS baselines had to be tied to the next pair along the road, with connections to the active network whenever we had sufficiently short baselines to it. With the area spanning from Tewkesbury and Milton Keynes in the south to the Scottish border in the north, a total of over 35.000 miles were driven to achieve the project!