Difficult Blunder Cases

In some instances, it is difficult to isolate the specific measurement that has caused the blunder. For example, you may have a loop with a large error; but when you analyze it, no one measurement stands out as a good candidate for the blunder. Nevertheless, even though you cannot narrow your candidates down to a single shot, you can still narrow it down to a hand full of shots. Here are some things you can do to help narrow the candidates:

1. Large Errors. Focus on loops that have errors greater than one standard deviation.

2. Large Improvements. Look for "Changes" that cause high ratios of improvement.

3. Similar Measurements. Look for situations where there are similar changes to the same measurement over several shots. For example, if you see four shots with 10-foot changes to the length, chances are very good that there is a 10-foot error in one of those shots.

4. Similar Types Of Measurements. Look for situations where most of the changes are to the same type of measurement. For example, if all the changes are to the azimuth measurement, then it is very likely that there is a blunder in the azimuth.

5. Shared Shots. Look for situations where two or more loops share the same shot. You can do this using the intersect option. If two or more loops indicate a blunder on the same shot and measurement, chances are very good that a blunder exists in that shot.