The key to systematic errors is that they are constant and consistent. If you understand what has caused the systematic error, you can remove it from each shot with simple math. For example, if the compass has a five degree clockwise bias, you simply subtract five degrees from each azimuth. Blunders are fundamental errors in surveying process. Blunders are usually caused by human errors.
Blunders are mistakes in the processing of taking, reading, transcribing or recording survey data.
Most programs use a process for closing loops called Minimizing Least Squares . Least Squares works by solving a large equation that take into account all the redundant data and minimizes the errors. Least Squares assumes that the errors in the survey are random. If the errors are not random, the data violates the mathematical model of Least Squares and the process will not work properly. As a result, if you are going to use Least Squares, special steps must be taken to detect any blunders and compensate for them.