Estimating 1/2 mile point on final

[chris_dixon]

I've recently been reading Making Perfect Landings in Light Airplanes which has been helping me along with some tips on good (but not prefect!) landings.
One thing that I'm struggling to understand is a tip that you pick a point 1/2 mile from your touchdown point as you enter the pattern and then whatever else happens aim to be a certain height (say 400') above this on final.

This seems sensible, but the issue I have is how to estimate that 1/2 mile with any degree of reliability, especially when you're over unfamiliar ground. I could work it out at my home field, but I guess my landings should be ok there anyway. do you use airspeed, or some other technique?

Could someone else who uses this or similar technique give me a pointer?

[4015]

I use a map; work out a half mile from the threshold and mark it or look for something nearby to reference. I do this with the alternates too.

Things like roundabouts, adjacent junctions, rivers, edges of towns etc. all work fine.

The problem with using the runway perspective is that all runways have a different one (Human performance and limitations books cover this quite well). And airspeed, I'm a bit confused as to how you could use this as a marker for distance?

[Dan the weegie]

Ask a local flying instructor as to what they use as a visual ref. It might not be half a mile but if it's not then just change the height so that it's on the right profile.

You can also use the published length of the runway to help you estimate the correct distance.

Either way after a load of circuits you'll get it spot on most places adjusting for rwy length and width.

[pudoc]

A lot of small airfields have websites which details their circuit. "Cross the motorway at 400ft" etc.

I find it hard to judge range as well, I guess it's something that comes with experience.

[UncleNobby]

How long is the runway? If the runway is 5000 ft, imagine another half a runway added on to the approach end! 2500/3000 feet is another runway length away........you get the picture......judgement comes with experience.