HPC Levelling
HPC Levelling Spreadsheet
Those students and independent learners undertaking this task in the BTEC ICT unit, that have little or no experience of setting out and levelling and who have not yet undertaken the BTEC Levelling unit can get some assistance with understanding the booking of levelling data (here).
The HPC levelling spreadsheet is set out as the example shown and should fill an A4 sheet. A printable copy is available and can be downloaded from (here).
The sheet is set out with the top section for general survey information. The bottom few rows are reserved for the error and misclosure checking.
The central section is for the levelling data, divided into standard columns as shown. The key is the development of the formula for the HPC and RL columns.
The HPC column formula checks to see IF there is a value in the BS cell and if so adds it to the current RL for a new HPC or ELSE uses the previous HPC. The formula also checks that if there is not a BS value is there a FS reading, IF so then you may have finished so HPC is set to zero.
The RL column checks to see IF there is either an IS or FS and If so then the RL for this row is calculated by deducting that value from the previous row HPC or ELSE the PL is set to zero.
An Excel spreadsheet version is available (here) with video demonstration (here)
Error Checking
There are two error checking routines in the bottom section of the sheet.
Misclosure The checking for the misclosure error is done by counting the number of set-ups or change points (this can be done by counting the number of back sight readings - COUNT()) and then taking the square root of this and adding a recognised amount to give the acceptable allowance for misclosure. SQRT(COUNT(BS))x5
The amount that is added to the square root is dependant on the size of the survey and what is deemed to be acceptable.
Calculation Errors When undertaking manual processing of levelling data then is is possible to create errors in the data with calculation or arithmetic mistakes. This spreadsheet will simulate to see if the calculations are TRUE by getting the total IS adding the total FS and the total RL's (excluding the first given RL) and comparing it to the total in the HPC Column.