[WaltN]

Goku, on 26 September 2016 - 04:21 AM, said:

But what is wrong with current values?
https://en.wikipedia...ki/Grade_(slope)#Nomenclature
I have 2,3 and 4 options:
2 and 3 -> Permile xy.z = percent x.yz
4 -> the second box.

There is a great deal of confusion in the literature about what "run" is. Some say it's the distance along the hypotenuse of the right triangle. (After all, that's the distance the train "runs.") Others say "run" is the base of the right triangle. The sine of the angle will be rise/run in the first case, and the tangent of the angle will be rise/run in the second case.

Now, for typical railroad grades, the angle is small, and the sine, tangent, and angle (in radians) are approximately equal. But for those of us who model inclined plane railroads, the distinction is important.

So, without making a survey of how many in Case 1 and how many in Case 2, the important thing is for you to carefully and precisely define what "run" means for your editor. (All it takes is basic trigonometry to shuttle back and forth.)

By the way, the recent Windows 10 "Anniversary Update" (1607) put the kuybosh on my use of the MSTS RE. I'll be watching this project with a great deal of interest.

[Goku]

In my editor "run" is track length. It is hypotenuse, not triangle base.

[WaltN]

Goku, on 26 September 2016 - 05:53 AM, said:

In my editor "run" is track length. It is hypotenuse, not triangle base.

That's the way I think of it. Hooray!

Also, although the Wikipedia article initially says run is the horizontal distance, later it says, "Railway gradients are usually expressed in terms of the rise in relation to the distance along the track as a practical measure." The track follows the slope.

[Genma Saotome]

I think the key question is given a handful of examples from KUJU's RE, what are the equivalent values in this program?

[Goku]

WaltN, on 26 September 2016 - 07:32 AM, said:

Also, although the Wikipedia article initially says run is the horizontal distance, later it says, "Railway gradients are usually expressed in terms of the rise in relation to the distance along the track as a practical measure." The track follows the slope.

The difference is 0.03% for 2.5 percent gradient (25 permile is max for heavy rail in my country), so IMO thinking about it is not important. For 5 percent (50 permile - common for trams) it is 3% difference.

[Gman347]

I do not claim any expertise in railroad terminology but in the architectural profession run is considered to be the horizontal dimension and rise the change in height. The percent of gradient is then taken as the rise divided by the run. For a route builder the required vertical rise of the grade is a known as is the horizontal distance between the two points over which the rise occurs. These are the two meaningful dimensions and rise divided by horizontal dimension provides the percent of gradient. Alternatively, the horizontal distance needed to maintain a predetermined gradient is simply the rise divided by that gradient. The hypotenuse is a not really relevant unknown and calculating it is an additional unnecessary step. That being said it is true that for the relatively shallow gradient to which railroad right of way must be maintained the error in any case will be very small.

Just my two cents.

[Goku]

Gman347, on 26 September 2016 - 09:52 AM, said:

The hypotenuse is a not really relevant unknown and calculating it is an additional unnecessary step.

It is not additional step.
How it works now:

// set vector 0, 0, 1000:
float vect[3] = { 0, 0, 1000 }; 
// rotate it using track quaternion:
Vec3::transformQuat(vect, vect, track->qDirection);
// vect[1] is now permile value ( hypotenuse / rise ). 
// now calculate ratio:
oneInXm = 1000.0/vect[1];

[Gman347]

Please don't misunderstand my comment. I am not questioning how the program works, nor was I being critical. I was just making the observation that as a route builder the two things I would likely know are the distance between two points and the rise that is needed between those points and I would calculate the gradient as the ratio of those two numbers. I guess I am just remembering working with those variables in my model railroad days. Back then a maximum gradient would have been established and the total horizontal length of track needed was calculated based upon the desired rise. I would not need to know the hypotenuse of the triangle and it would have been an extra step for me to calculate it. I has always been my understanding that the locating engineers working for real railroads, planning a route in an area with changing terrain, basically dealt with the situation in similar fashion.

[Jovet]

Goku, on 26 September 2016 - 05:53 AM, said:

In my editor "run" is track length. It is hypotenuse, not triangle base.

I want to add that since MSTS uses fixed track pieces, this is a natural happening. In an ideal world the "run" would be the triangle base. But since doing that correctly would require numerous odd-length pieces of track, it isn't practical.

[Lindsayts]

Gman347, on 26 September 2016 - 09:52 AM, said:

I do not claim any expertise in railroad terminology but in the architectural profession run is considered to be the horizontal dimension and rise the change in height. The percent of gradient is then taken as the rise divided by the run. For a route builder the required vertical rise of the grade is a known as is the horizontal distance between the two points over which the rise occurs. These are the two meaningful dimensions and rise divided by horizontal dimension provides the percent of gradient. Alternatively, the horizontal distance needed to maintain a predetermined gradient is simply the rise divided by that gradient. The hypotenuse is a not really relevant unknown and calculating it is an additional unnecessary step. That being said it is true that for the relatively shallow gradient to which railroad right of way must be maintained the error in any case will be very small.

Just my two cents.

When railways were laid out in the pre computor days, surely the horizontal distance would NOT have been known. The line was laid out with a team of surveyors, pegging out the line using chains and a set of theodelites. For important projects particularly over difficult terrain a number teams were used and the results compared to get greater accuracy. Due to this method of laying out the line only the distance the line actual covered would have been known, ie in hilly terrain horizontal distance would have had to be calcaulated. As Goku has already mentioned the difference between the true track distance and the actual horizontal distance is not really significant. Note : if you set up a route using markers taken from Google earth as long as one can set the grades correct th actual track distance should not really be an issue.

The error caused by the simplistic world model used by MSTS in most cases would produce an error greater then this error.

Incedently I have measured on Google earth the actual horizontal distance (Note 1) of the line Between Melbourne in Victoria Australia to Wagga in New South Wales, The rail distance i something around 450 kilmetres the measured distance varied by less than 300 metres, this corresponds to an error of around 0.06% an amount that would be insignificant in a route that long.

Note 1: The length was measrured of all straights between the points when a curve ended and the next curve started, the length over curves was measured in 100metre or so sections.

Lindsay