How to read track charts, gradients

[rwk]

I found this track chart from 1982 of Conrail lines including the Raritan Valley Line operated directly by NJ Transit since 1983, and I'm wondering how to read the gradients. It does have a roller coaster like profile on the section west of Raritan around the White House and Lebanon stations with some flat parts and some gradients, but I want to know what vertex heights to use based on the track chart, I'm using 22 PE and there is also a gradient tool to tell you the gradient. Here is the track chart https://multimodalways.org/docs/rai...ts/CR NJ Commuter Region Track Chart 1982.pdf Scroll down to page 14 or so for the Raritan Valley Line section. I'm also looking at Google Earth Pro for gradients but it seems that the gradient numbers are different than what the Trainz DEM has. Are Trainz elevation heights based on sea level, so elevation 0 is sea level?

 

[OddRails]

Yes, Trainz creates baseboards with a default level of 0 meters.

You will get to do some conversions between metric and imperial measurement units. Your track chart has elevation in feet and mile markers while Trainz uses meters and kilometers. To convert the elevations in feet to meters: divide feet by 3.28084 to get meters. Then your elevations might match what you see in Trainz surveyor. If you're using TransDEM you can select either metric or feet units using the Options>Settings menu

But your track chart looks like it gives the gradient percentage. Between mile markers 49 and 48 a gradient of 0.99% is printed just above the line. I had trouble reading the numbers on the chart and had to change the 48 marker elevation until I found the correct that gave a value near 0.99%.

mile 48 shows an elevation of 280.81 ft which is 88.39 meters in Trainz
mile 49 shows an elevation of 343.30 ft which is 104.64 meters in Trainz

You can do --- (rise/run)*100=gradient in percent --- calculations to help figure out smudged numbers.

 

[RPearson]

Hi rwk, long time. Good to see you still here. I've been away from Trainz for several years now. I might start dropping in once in awhile. I'm not sure yet.

Basically as OddRails said. I read a slightly different elevation for MP48 290.81 ft but same for MP49 343.30 ft. And 1 mile between MP48 and 49 is 5280 ft. So gradient is (343.30-290.81)/5280 = 0.009941. As a percent Gradient = 0.99% rounded to 2 decimal places as per diagram. Trainz does use meters for elevations even if you select imperial units for the display. In meters: MP48 88.64 m and MP49 104.64 m and 1 mile is 1609.36 m. Plug those into formula and get the same results for gradient (104.64-88.64)/1609.36 = 0.009942. Gradient = 0.99%.

The numbers on the diagram are difficult to read so you might have to adjust a few in spots. The other problem is that elevations indicated at points other than Mile Posts don't show the distance from the horizontal reference location for the diagram. You will have to measure it some how. Scaling the drawing or calculating intersection of gradients from the MP and gradient data maybe. I had similar problems with PRR track diagrams I used for gradients between Lewistown and Huntingdon, PA. I put the data in a spreadsheet which made the calcs easier.

I used the elevation numbers as top of track rail values. Depending on how fills and cuts are incorporated in the dem data you use for the terrain on the Train baseboards the indicated elevations probably won't match up with the track diagram. For my routes I usually set the track elevations and grades along the whole route and then adjust the terrain created from dem data to fit the track locally. I use track with attached fill a lot. It creates an automatic fill between terrain and track ballast when you lay the track. A lot of work but the grades are accurate.

Bob Pearson

 

[OddRails]

@RPearson Oops. I changed the elevation to 290 in my calculations but didn't change what I posted. Thanks for catching that.
Thanks also for mentioning the the height as top of rail values. I didn't think of that at all.

 

[rwk]

I noticed on a DEM of Northeastern PA (I added on to the Reading and Northern DLS route in 19 which I moved over to 22 PE) that the map overlay I used several years ago in TransDEM (I no longer have access to it and would have to buy a new version)is is off a bit compared with where the railroad grade actually is. It's just the way the map creators originally drew the lines for the railroad which don't exactly line up with the railroad grade on the DEM in Trainz in spots. I can somewhat follow the cuts and fills though to lay the track properly.

 

[JCitron]

I noticed on a DEM of Northeastern PA (I added on to the Reading and Northern DLS route in 19 which I moved over to 22 PE) that the map overlay I used several years ago in TransDEM (I no longer have access to it and would have to buy a new version)is is off a bit compared with where the railroad grade actually is. It's just the way the map creators originally drew the lines for the railroad which don't exactly line up with the railroad grade on the DEM in Trainz in spots. I can somewhat follow the cuts and fills though to lay the track properly.

If this was done using the old HOG method, the maps can be way off compared to the terrain. Using TransDEM and topographic maps is the most accurate for route building.