When approaching an uncontrolled airport especially, standard procedure demands to make the first call 10 miles out announcing my location, entry procedure, etc. and then more calls at 5 miles, 2 miles, etc. I find myself having a hard time estimating how far I am from an airport so I can announce my position. The same applies when I'm asked to report a 8 mile final in a controlled airport. I'm curious how others do it and if there's a more reliable way to judge distance from an airport. Thanks.
On a US Sectional, the length of the shorter part of your thumb, where the fingernail is, is about 10 nautical miles (check yours against the chart on the bottom). If you are keeping track of where you are along your pre-drawn course line, you quickly check your thumb against the sectional for a distance.
My GPS tells me the distance.
Otherwise, my experience says:
15 miles (and about 3,000 AGL) is where I'm not entirely sure I have the airport picked out.
10 miles is where I can see the airport, but not pick out specific details and airplanes.
5 miles is where I can see the airport clearly, and setup for the centerline.