The difference between Height of Collimation Method (HCM) and Rise and Fall Method (RFM) are as follows:
HCM :It is more rapid and saves a considerable time and labour.
RFM : It is laborious as the staff reading of each station is compared to get a rise or fall.
HCM : It is well adopted for reduction of levels for construction work such as longitudinal or cross-section levelling operations.
RFM : It is well adopted for determining the difference in levels of two points where precision is required.
HCM : There is no check on reduction of R.L. of intermediate stations.
RFM : There is a complete check on the reduction of RL of the intermediate stations.
HCM : There are only two arithmetical checks i.e. the difference between the sum of the fore sights must be equal to be the difference in R.L. of the last station and first station.
RFM : There are three arithmetical checks i.e the difference between the sum of the back sights and the sum of fore sights must be equal to the difference between the sum of the rises and the sum of the falls as well as it must also be equal to the difference in RL of the last station and first station.
HCM : Errors if any in intermediate sights are not detected.
RFM : Errors in intermediate sights are noticed as these are used for finding out rises and falls.
HCM :It is more rapid and saves a considerable time and labour.
RFM : It is laborious as the staff reading of each station is compared to get a rise or fall.
HCM : It is well adopted for reduction of levels for construction work such as longitudinal or cross-section levelling operations.
RFM : It is well adopted for determining the difference in levels of two points where precision is required.
HCM : There is no check on reduction of R.L. of intermediate stations.
RFM : There is a complete check on the reduction of RL of the intermediate stations.
HCM : There are only two arithmetical checks i.e. the difference between the sum of the fore sights must be equal to be the difference in R.L. of the last station and first station.
RFM : There are three arithmetical checks i.e the difference between the sum of the back sights and the sum of fore sights must be equal to the difference between the sum of the rises and the sum of the falls as well as it must also be equal to the difference in RL of the last station and first station.
HCM : Errors if any in intermediate sights are not detected.
RFM : Errors in intermediate sights are noticed as these are used for finding out rises and falls.
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