Construction surveying

Construction surveying or building surveying (otherwise known as 'staking', 'stake-out', 'lay-out', 'setting-out' or 'BS') is to stake out reference points and markers that will guide the construction of new structures such as roads or buildings. These markers are usually staked out according to a suitable coordinate system selected for the project. Construction surveying or building surveying (otherwise known as 'staking', 'stake-out', 'lay-out', 'setting-out' or 'BS') is to stake out reference points and markers that will guide the construction of new structures such as roads or buildings. These markers are usually staked out according to a suitable coordinate system selected for the project. Land surveys and surveys of existing conditions are generally performed according to geodesic coordinates. However for the purposes of construction a more suitable coordinate system will often be used. During construction surveying, the surveyor will often have to convert from geodesic coordinates to the coordinate system used for that project. In the case of roads or other linear infrastructure, a chainage (derived from Gunter's Chain - 1 chain is equal to 66 feet or 100 links) will be established, often to correspond with the centre line of the road or pipeline. During construction, structures would then be located in terms of chainage, offset and elevation. Offset is said to be 'left' or 'right' relative to someone standing on the chainage line who is looking in the direction of increasing chainage. Plans would often show plan views (viewed from above), profile views (a 'transparent' section view collapsing all section views of the road parallel to the chainage) or cross-section views (a 'true' section view perpendicular to the chainage). In a plan view, chainage generally increases from left to right, or from the bottom to the top of the plan. Profiles are shown with the chainage increasing from left to right, and cross-sections are shown as if the viewer is looking in the direction of increasing chainage (so that the 'left' offset is to the left and the 'right' offset is to the right).