For surveying, we need to have some prerequisite conditions. If these conditions are not met we can have a huge variation in result. Therefore we have to apply corrections to get the true result.
1) A tape accurate to 0.00305m or 0.01 ft should be used.
2) Tension of the tape should be about 66.7N or 15 lb.
3) Temperature should be determined within 5.56°C or 10°F
4) The slope of the ground, should be within 2 percent
On ground these are nearly impossible to achieve and thus corrections need to be applied.