[HOT] leisure=common (Helipad)
markcupitt at gmail.com
Thu Feb 19 13:33:31 UTC 2015
It is actually a quite difficult thing to specify because the performance
of helicopters varies dramatically.
To explain ..
Temperature and altitude play a very large role, basically the higer you
are, the thinner the air, the less bite on the rotors.
There is a measure called density altitude, which is where the temperature
comes in, the hotter it is, the thinner the air = same issue as above
The combination of the two is one of the most important things a pilot
There are very few helicopters that routinely take off vertically,
generally they will rise to a hover then move forward in ground effect
(which is like a cushion of air between the rotors and the ground). This
actually allows heavier helicopters to take off without needing so much
power for a vertical climb out, and which many cannot do for performance
reasons and options if they have an engine failure.
Weight is another very critical factor, but that is an operational matter
we will never know anything about and is often driven by temperature and
altitude issues as well.
So the bottom line is not so much the actual space, it is the approach and
departure paths that are the most critical.
Some choppers can come right in and drop and depart vertically, say into a
foot ball field surrounded by a stadium.
However, I know the pilots would much prefer to have options for approach
and departure that gives them a way in and out without having to climb
vertically, and probably means that they can carry more in terms of
payload, people, etc.
Again, this is all very much dependent on the type of helicopter, some can
do it, others not depending on their performance envelopes.
If we map the buildings around any marked landing areas, then any pilot
will know immediately he is dealing with obstacles and can plan his flight
accordingly. Height of those building is a VERY useful piece of
information, but one we are unlikely to be able to provide from Sat images
The other thing we can do is map power lines, other buildings, and groups
of trees around the LZ's to show possible approach and departure paths,
this would be very useful information for mission planners and pilots
Hope that helps
"If we change the world, let it bear the mark of our intelligence"
See me on Open StreetMap <https://www.openstreetmap.org/user/Mark_Cupitt>
On Thu, Feb 19, 2015 at 7:31 PM, john whelan <jwhelan0112 at gmail.com> wrote:
> Project 892 task 23 is an example. The following question got sent to me
> probably because I've been validating merrily away.
> >What is the minimum diameter for a Helipad (leisure=common)?
> Based on my own experience of visiting a remote Scottish Island the local
> football pitch, being smooth, level and firm enough was the designated
> helicopter landing place.
> I'm not sure that you can tell enough from satellite imagery that a
> certain bit of ground is smooth, level and firm enough to take the weight
> of a helicopter. However we seem to have a fair number of circular
> leisure=common areas tagged near fairly small villages.
> So can we flesh out a bit more of the requirements please and better
> identify what we should be looking for and mapping.
> Thanks John
> HOT mailing list
> HOT at openstreetmap.org
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