Surveying Lectures
Surveying Lectures ➢ Chainage corrections 𝑤 2 𝑙3
o Sag correction = − 24𝑝2
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o Temperature correction = 𝑘(𝑇𝑓 − 𝑇𝑠)𝐿 𝐿(𝑃𝑓−𝑃𝑠) o Tension correction = 𝐴𝐸 Angles are between lines and are what are observed using theodolites, while Bearings are the directions of these angle lines, usually to a common datum – grid north Rise and fall method CHECK: o Sum(BS) – Sum(FS) = Sum(rise) – Sum(fall) = Last RL – First RL Height of Collimation Method is used for finding the RLs of numerous intermediate points whose precise location is not required but whose level is required HOC = RL(inst) + BS RL(is) = HOC – IS RL(fs) = HOC – IS On a closed traverse the Misclosure is calculated by comparing the start and finished RL On a open traverse the misclosure is calculated by first knowing the RL’s of both the first and last points Allowable misclosure = 𝑚√𝑛 , where m = 5 and n = no of stations A Datum is a system which allows the location of latitudes and longitudes (and heights) to be identified onto the surface of the Earth Map Projections: o Equal-area projections preserve true areas o Conformal projections preserve true shape o Azimuthal projections preserve true compass direction from the centre Tacheometry is the process used to collect topographical data over a site before designing, setting out and construction. When reading the e-staff through a theodolite, the mean of the upper and lower hairs should equal the middle reading If S is your staff reading then: o Slope Distance = 100𝑆 cos 𝜃 o Horizontal Distance = 100𝑆 cos 2 𝜃 o ∆ℎ = 𝑆𝐷 sin 𝜃 (delta)eastings = HDsin 𝜃 (delta)northings = HDcos 𝜃
o Sag correction = − 24𝑝2
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o Temperature correction = 𝑘(𝑇𝑓 − 𝑇𝑠)𝐿 𝐿(𝑃𝑓−𝑃𝑠) o Tension correction = 𝐴𝐸 Angles are between lines and are what are observed using theodolites, while Bearings are the directions of these angle lines, usually to a common datum – grid north Rise and fall method CHECK: o Sum(BS) – Sum(FS) = Sum(rise) – Sum(fall) = Last RL – First RL Height of Collimation Method is used for finding the RLs of numerous intermediate points whose precise location is not required but whose level is required HOC = RL(inst) + BS RL(is) = HOC – IS RL(fs) = HOC – IS On a closed traverse the Misclosure is calculated by comparing the start and finished RL On a open traverse the misclosure is calculated by first knowing the RL’s of both the first and last points Allowable misclosure = 𝑚√𝑛 , where m = 5 and n = no of stations A Datum is a system which allows the location of latitudes and longitudes (and heights) to be identified onto the surface of the Earth Map Projections: o Equal-area projections preserve true areas o Conformal projections preserve true shape o Azimuthal projections preserve true compass direction from the centre Tacheometry is the process used to collect topographical data over a site before designing, setting out and construction. When reading the e-staff through a theodolite, the mean of the upper and lower hairs should equal the middle reading If S is your staff reading then: o Slope Distance = 100𝑆 cos 𝜃 o Horizontal Distance = 100𝑆 cos 2 𝜃 o ∆ℎ = 𝑆𝐷 sin 𝜃 (delta)eastings = HDsin 𝜃 (delta)northings = HDcos 𝜃
