Corrections for Baseline Measurement 

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It is necessary to apply the following corrections to the field measurements of base line order its true length:
It may be noted that each section of a base line is separately corrected. 
1. Baseline Correction for Absolute Length:It is given by the formula Where CA = Correction for absolute length Sign of CA is the same as that of C Nominal length: The designated length i.e 50 tape, 100 tape (30 m tape) Absolute length: The actual length under specified conditions 

2. Correction for Temperature:It is given by the formula Where Steel = 0.00000990.000012/c Steel = 0.0000055 – 0.0000070/ F The sign of ‘Ct’ is plus or minus according to as ‘Tm’ is greater or less then ‘to’ 3. Correction for Pull or Tension Where E steel = 21 x 105 kg / cm^{2} E steel = 30 x 106 /bs/in^{2} The sing of this correction is always plus (T) as the effect of pull is to increase the length of the tape and consequently to decrease the measured length of the base. 4. Correction for Sag:Correction for sag is the deference in length between the are and its chord i.e b/t the curved length of the laps and the distance between the supports. It’s us required only when the tape is suspended during measurement. Since the effect of sag is to make the measured length too large, it is always subtractive. It is given by the formula. Where
Cs = Correction for Sag W = wt of tape b/t supports. Sag correction per tape length is
Total sag correction to measures length Cs=N x Cs/ + Cs// Where N = no of whole tape length Normal tension: The normal tension of a tape is a tension which will cause the effects of pull and sag to neutralize each other. It may be obtained by equating the corrections for pull and sag Where Pn = normal tension Pn is determine by trial 5. Correction for Slope or Vertical Alignment: This correction is required when the points of supports are not exactly at the same level
