Using this index correction, we can often find a more probable search area for the original corner. When a definite pattern has been established and a specific linear or angular amount is determined, these may be applied in the form of an index correction to situations where a corner is to be restored. In such situations the record with the index correction equals the true bearing and distance to establish the corner point search area.

The retracement data divided by the record equals the factor that compares the length of the record chain with the retracement chain.

If this factor is more than one, the record must be lengthened, less than one, the record must be shortened. A factor of 0.99500 indicates the record chain was only 99 1/2 links in length.