I recently did a level survey however am a little stumped over a calculation. I am trying to calculate the Reduced Level using the "Height of Instrument" method. I know how to do the calculations etc. so I am not asking for this to be done for me. It is more of a general question about this sort of situation. Below is an image attached of ALL the information recorded however it is obvious, without a reduced level I am unable to proceed in the calculations (or at least I think so). To calculate the Reduced level under these restricting circumstances how would one go about this? Do I take the original height of the instrument as the original backsight reading then calculate the reduced level this way? As you can see from the example here the height of instrument and reduced level are essential to do this pretty simple calculation. Am I overlooking something small? can anybody shed light on how exactly one would go about calculating the initial reduced level and height of instrument with the given information attached because I am completely lost. Thank you.