Track Crawling is commonly onserved as the pilot placing finger on map and looking at the ground outside and based on the observed progress of the aircraft, the finger is moved across the chart. Corrections are plentiful and ad-hoc and the system is not desireable because;
1. All the pilot looks at is the ground and the map for most of the time so lookout for traffic is poor.
2. The heading wanders frequently and consequently even if the pilot wanted to completean adjustment, they can't really tell what heading they have flown for the last x minutes.
3. Not being able to spot what the map says should be there leads to panic or the pilot sees what he wants to see and the panic is delayed by some minutes.
That is track crawling.
What is not track crawling is...........
at the planning stage saying that there is a big mountain range there. The minimum safe level based on visual navigation / DR is 5000ft. I plan to fly a heading that will follow the coast from here to there and thus I can ignore the mountains and my minimum level is 1500ft.
or
At the planning stage deciding that having to keep 5nm away from that zone is causing an unnecessary delay because I can fly to that motorway junction and then fly a heading that follows the motorway to that junction where is simply head off on a steady heading again and that will ensure that I do not infringe the zone despite being only some 2nm from the boundary at one point.
or,
the vis is not as good as planned and I am neing forced to operate at minimum level. Rather than fly a heading direct to my airfield, I will fly north along this road for 20nm and then at that junction fly east for 30nm to the airfield.
None of the above are track crawling they are legitimate navigation techniques (usually called handrailing because that is what you are doing) used to resolved a particular issue.
What most schools fail to tell students is that it is perfectly OK to use the above at PPL and CPL level. However, there is a requirement during training and during the test to demonstrate DR and that can not be done while handrailing.
Regards,
DFC