Loop Closing Options
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One of the features of the COMPASS Loop Closer is the program closes the best loops first. This prevents bad loops from distorting good loops. So, part of the process of closing loops is choosing which loops are good and which loops are bad. There are several different methods of evaluating loop quality. Some people prefer different methods.
This option allows you choose which method the Loop Closer uses to evaluate loops. To select a particular method, just click on the corresponding radio button. Here is an explanation of each method:
1. Standard Deviation. The Standard Deviation method chooses the best loops based on statistics. With the standard deviation method, the program makes an error prediction for each loop based on the quality of the surveying instruments. The better a loop matches this prediction, the better the loop is. From a mathematical standpoint, this method is the best method. It is, however, slightly slower than the other methods.
2. Percent Error. The percent error method chooses the best loops based on the percent error for each loop. The method takes the error in a loop and divides it by the length of the loop. In other words, it measures what percentage of each foot or meter surveyed is error. Percent is not the best method for evaluating loop quality, but it is still used by many people because it is easy to understand. As a result, it is included as an option.
3. Absolute Error. This method simply uses the size of the loop error, without taking into account the length of the loop or any other factors. Generally, this method is only useful when you have loops with large vertical errors and small east/north errors. Because of the way the other methods combine the east, north and vertical parts of the error, they can mask large vertical errors.