Uphill/Downhill driving percieved distance.

[MaxFlight]

Hey guys,

Something I've thought about almost every time I drive moderately uphill/downhill shots... You know how a 300ft uphill shot can seem more like 350 feet? There must be some sort of mathematical equation to calculate the "perceived" distance compared to a flat shot.
For instance, say there was 25º incline on a 300 foot shot. What kind of power would you need compared to a flat 300 foot shot? Does the same amount of power that would normally get you 300ft flat, only get you 250ft on that incline? Of course there are other variables, such as disc choice, angle ect... But pretend those variables are exactly the same.

Same for downhill shots. A 300 foot downhill shot can easily seem more like 200 feet.

Any physics geeks in here?

Cheers!

 

[Cgkdisc]

Rough rule of thumb for some designers has been 3 to 1 for elevations 10% or less. For example, 10 ft rise/fall over 300 feet would add/subtract 30 feet (3x10) to/from the 300 feet.

 

[brutalbrutus]

Rough rule of thumb for some designers has been 3 to 1 for elevations 10% or less. For example, 10 ft rise/fall over 300 feet would add/subtract 30 feet (3x10) to/from the 300 feet.

Sounds about right. In golf, for every 10ft rise/fall you would go up/down a club and most people have about a 10yd(30ft) difference between irons.

 

[Cgkdisc]

Past a 10% grade, the change is non-linear to the point where you can't throw hard enough reach a ledge 150' vertically above you or you only need to barely drop a disc off a vertical cliff.

 

[Flick Maniac]

Two fine ideas for fun holes.

 

[DavidSauls]

Past a 10% grade, the change is non-linear to the point where you can't throw hard enough reach a ledge 150' vertically above you or you only need to barely drop a disc off a vertical cliff.

The 3/1 is just a rule of thumb, and good enough to work with. But were it worthwhile to find a more accurate figure, I suspect there would be percentages involved.

We have a good downhill test hole---fairly open, 60' elevation drop over 400', then flat. I've noticed that people who throw further on flat land, seem to get a larger boost than weaklings like me.

I'm not as sure about the uphill, because the uphill holes I play tend to have other constraints that make it harder to judge.

 

[d11rok]

Pythagorean theorem? You can get the height change, and can get the hypotenuse (the actual distance). The remaining leg would be the horizontal distance without taking height into account.

For review, a2 + b2 = c2. You'll be solving for b to get the horizontal distance.

This brings up a related question: do you want distance markers to state the horizontal distance alone or the hypotenuse?

 

[JC17393]

Pythagorean theorem? You can get the height change, and can get the hypotenuse (the actual distance). The remaining leg would be the horizontal distance without taking height into account.

For review, a2 + b2 = c2. You'll be solving for b to get the horizontal distance.

This brings up a related question: do you want distance markers to state the horizontal distance alone or the hypotenuse?

I don't think this is the issue at hand. Generally speaking, if you're measuring a hole that has an elevation change, you're measuring it on the hypotenuse already. Mainly because how are you measuring horizontal distance in such a case? Either you'd be measuring to a space in midair above the target (downhill throw) or a space deep in the ground below the target (uphill throw). Not really practical or possible in most cases. Whether you're measuring with a wheel, a tape, or a laser rangefinder, you're measuring point to point on the playing surface.

What we're talking is effective distance. Uphill and downhill throws that are affected more significantly by things like disc angle and gravity. You will get more distance throwing downhill with disc X than you do on flat ground. You will get less distance throwing uphill with disc X than you do on flat ground. The question is how much are you gaining/losing as it relates to the change of elevation.

 

[d11rok]

Jc,
Thanks for clarifying. I do disagree on it being difficult to find horizontal distance- Google maps does this quite well unless the user cannt discern a basket/tee location on the map itself.

Accurately finding the added or subtracted difference in distance is relatively easy as long as you have the initial velocity at release and the coefficient of drag (which for a disc is around 1.1). You can calculate a flat distance based on that (I'd encourage those that are interested to visit the NASA website for more detailed information). Then to calculate the additional added distance a down hill throw would give you, simply take the vertical distance, determine how long it takes the frisbee to fall that amount due to gravity. Plug that time into the first equation and you have your answer. For uphill, you subtract the time from the horizontal flight equation

This assumes no lift from the disc, which is a big assumption, obviously, as that is how it stays airborne. You can in fact take that into account, but the math gets trickier as the lift is less towards the end of flight, gyroscopic precession, blah blah blah.

 

[Zanguini]

About how ever far i am short of the hole is how much extra distance up hill is worth....


300 ft hole left 50 ft short...

I would have parked that hole if it were flat... the hole really plays like 350....

200 ft hole left 50 ft short....

I would have parked that hole if it were flat... the hole really plays like 250... chose the wrong disc because of it.

Works the opposite way with a downhill grade...

300 ft hole left 50 ft long...

Man i really got into that one.... that's got to be at least 350.. alright best drive of the day....

 

[retleftolc]

Kind of what d11rok said covers it. Specifically for a given amount of velocity with regard to actual distance (which most players call "power").

Since players think of power in terms of how far they, or player x, can throw a disc, it is much more functional to use a general rule of thumb applied to their power level.

 

[DavidSauls]

Almost makes me want to drag some players out to some hills and test it.

Almost.

 

[Cgkdisc]

Potential study for a Master's or Doctoral thesis?

 

[Karl]

Google maps does this quite well unless the user cannt discern a basket/tee location on the map itself.

Not a big fan of Google for distances. Using both a steel tape and a theodolite (and not bothering to do this unless the hole was dead flat with virtually no undulations) have checked numerous holes on numerous courses listed as 'hole measurements taken using Google maps' and have found them to be inaccurate. The funny thing about it is the Google measurements aren't always off in the same direction (all "high" or all "low").
Now while you might think this isn't a big deal, personally if a 280ft hole is off by 7+% that probably has me throwing a different disc (especially OH), missing it by 20+ more ft (than I would have) and not having as good a shot at the birdie as I would have if I'd known the correct distance.
There's a reason why surveyors still have jobs .

 

[d11rok]

Interesting, although I can't imagine there being swaths of holes in disc golf that are free from obstruction and nearly flat

 

[DavidSauls]

There are whole swaths of the country that are nearly flat. I've played courses with multiple holes that were free from obstruction, at least as far as most people were getting off the tee.

If we really wanted to determine the effect of evolution, we wouldn't need swaths, though. Just enough, open enough for players to throw full power on their chosen route, to establish their average level distance.

Rarer would be the holes with known elevation change, and open enough to throw full power. You want an assortment of them, of various elevations.

 

[ToddL]

Jc,
Thanks for clarifying. I do disagree on it being difficult to find horizontal distance- Google maps does this quite well unless the user cannt discern a basket/tee location on the map itself.

It's not worth getting bogged down in the details here. There is a negligibly small difference between the horizontal leg and the hypotenuse on most disc golf holes.

A hole that is 300 ft horizontal and 60 ft vertical has a 306 ft hypotenuse. That's a HUGE elevation change for a relatively short hole. I don't think anyone would care which number is written down.

 

[Putt for D'oh]

Hey guys,

Of course there are other variables, such as disc choice, angle ect... But pretend those variables are exactly the same.

Same for downhill shots. A 300 foot downhill shot can easily seem more like 200 feet.

Cheers!

Part of the difficulty is because I don't know how you eliminate those variables. How long does the hole play? Depends on which variables you want to change.
Generally my personal experience is to see a lot more negative distance up hill than down hill will add for the same disc. But that is a lot of guessing on height of the slope and estimated distance which I'm probably not as accurate as I'd like to be let alone consistent throws.

My home course has no flat holes. Some have tee and basket at maybe the same elevation but there is either a hill or a valley in the middle. Disc selection makes the discussion on how the hole plays a bit odd. A really glidey mid can go really really far even with just a slight down hill slope, whereas a big driver might only get you an additional 20'.
We have a hole measured at 345'. I'm guessing about 8' down hill. I can reach it consistent with an OS teebird consistently. On a good rip 10-20' long. I've gone 100' past a few times with a Truth. So would I say it plays like 320' or 210'? Based on how I throw those discs on flat ground?

 

[DiscJunkie]

Seems like there would be a calculation for the extra force needed to shoot an object, like a bullet (which can be reasonably deduced to have zero lift and a quantifiable drag and weight), uphill to reach a certain target or distance.
Seems also that we could use that to get a rough estimate from that calculation, also understanding that discs have some lift/glide and differences might be applicable for different disc types.

Just thinking out loud...

 

[Central Scrutinizer]

There's a steep downhill hole at my buddy's course (Wild Haven in Manton, MI) that depends a lot on the wind speed and direction. If it's out of the west, I can pitch a putter down there. If it's strong and out of the east, I'm throwing an OS driver for the same result (It's Hole #3 on the original course for anybody familiar). I think it's about 300' but way, way downhill. One of my favorite holes!