Railroad track charts are relatively easy to obtain by spending a modest $$ amount. Typically less than $20 so now you are putting together a real route and you want it to be as accurate as possible. Curves are not usually a serious issue. You may see, for example, a 8 degree curve. Well, if you use Mtracks there is such a curve and you just select the pieces and have at it. Or you may see 5 degrees, 27 minutes. Well Mtracks does not have fractional degrees above 4, so using that constant of 1746 which was discussed elsewhere in surveying, just determine that 27/60 is .45, so 1746/5.45 = 320 meters. At this point, I would just use 300 meter pieces, but if you want to really split hairs you could use dynamic track. I almost always use the nearest default or Xtracks curve.
But gradients? So I look at the gradient line and it happens from studying the Chattanooga line over many years, I know that the descending grade from Cumberland Tunnel to Tantallon is about 1.8% on average. Fine on tangent track, but when it gets crooked, like around mile 90-91 where I find a series of curves, 5 degrees, 6 degrees-11 minutes, 7 degrees, and 5 degrees-26 minutes, the gradient is all over the place, -2.37%, many short pieces -1.75%, -2.45% etc. What this is, is a compensated grade. It does not matter much for trains going down grade, but climbing up, curvature adds friction which has the effect of increasing the gradient. Well, in ORTS, we don't have a compensation issue as far as I know, so there are two methods I have used. One is to use the average gradient between two points where the grade either changes from up to down, or down to up, or between mileposts. Google Earth is helpful in locating changes of gradient and you can download KMZ files of Topomaps from the USGS site and overlay these on Google Earth. Don't expect an exact alignment with your digitized route because it won't happen but it will be close enough to allow you to add markers where the major contour intervals cross the track line. This will be in feet, so divide by 3.28 to convert to meters, or some more recent maps are in meters. I find that just marking the elevation where there are changes and calculating the gradient does a great job. You can use Google Earth to measure the distance between points of the grade. So I have two points that I have marked on Google Earth. The measurement is 5,222' and the difference in elelvation is 29 meters or 95.12 feet. 95.12/5222 = 1.82%. I might have to adjus that a little but my target is to hit each elevation point within .5 meters or less.
Sufficiently confused? Well, my degree is in Electrical Engr. from a long time ago in 1960 and in 1957 as part of that I took elementary surveying which is more civil engineering related. In 34 years on the wide gauge, I worked as more of a Civil Engr.
Jerry
But gradients? So I look at the gradient line and it happens from studying the Chattanooga line over many years, I know that the descending grade from Cumberland Tunnel to Tantallon is about 1.8% on average. Fine on tangent track, but when it gets crooked, like around mile 90-91 where I find a series of curves, 5 degrees, 6 degrees-11 minutes, 7 degrees, and 5 degrees-26 minutes, the gradient is all over the place, -2.37%, many short pieces -1.75%, -2.45% etc. What this is, is a compensated grade. It does not matter much for trains going down grade, but climbing up, curvature adds friction which has the effect of increasing the gradient. Well, in ORTS, we don't have a compensation issue as far as I know, so there are two methods I have used. One is to use the average gradient between two points where the grade either changes from up to down, or down to up, or between mileposts. Google Earth is helpful in locating changes of gradient and you can download KMZ files of Topomaps from the USGS site and overlay these on Google Earth. Don't expect an exact alignment with your digitized route because it won't happen but it will be close enough to allow you to add markers where the major contour intervals cross the track line. This will be in feet, so divide by 3.28 to convert to meters, or some more recent maps are in meters. I find that just marking the elevation where there are changes and calculating the gradient does a great job. You can use Google Earth to measure the distance between points of the grade. So I have two points that I have marked on Google Earth. The measurement is 5,222' and the difference in elelvation is 29 meters or 95.12 feet. 95.12/5222 = 1.82%. I might have to adjus that a little but my target is to hit each elevation point within .5 meters or less.
Sufficiently confused? Well, my degree is in Electrical Engr. from a long time ago in 1960 and in 1957 as part of that I took elementary surveying which is more civil engineering related. In 34 years on the wide gauge, I worked as more of a Civil Engr.
Jerry
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