Positive or Negitive Grades

[dricketts]

How do you tell if laying a positive (up hill) or negative (downhill) grade when laying track adjusting the vertex height and get grade tool? It seems it changes depending which way you are facing in surveyor.

I just spent and hour laying several miles of winding track on a DEM map. Trying not to exceed a 1% downhill grade for the entire length. Come to find out after testing some sections are a positive (up hill) grade.

I can't seem to master the grade tools in surveyor. What's the trick?

 

[Dermmy]

If you are applying a grade you need to click just next to each spline vertex on the uphill (+ grade) or downhill (- grade) side of the vertex. The trick is that the grade is applied from the nearest vertex so if you click more than half way between, you will apply the opposite gradient.

It is very easy to click too far past the vertex on short lengths of track, or when hurrying, or when using a long low camera angle to get several spline points 'clicked' without moving the camera.

I find it easiest to work uphill. Starting at the bottom, apply say +1.00 (or whatever) clicking right behind each vertex moving steadily up the hill with a more-or-less straight down camera angle. I then check the grade by working back down the hill using the 'Get Grade' tool to check that I have -1.00 (or whatever) on each track segment all the way down...

Andy

 

[rjw1975]

In addition to what Dermmy said it`s been my experience that that I`ve had to check and make adjustments to the grade up to 3 times. If you have a section that needs to be adjusted I`ve found it best to go back to the start of your grade and adjust it in the same direction you laid the track in. That way you know the point the grade is starting/measuring from is correct, and you may find that some are easier if you adjust the vertex height manually using the check vertex height and apply vertex height tools. I`ve found that sometimes track sections won`t change grade without changing the ones next to them.

 

[a2233138]

In addition to what Dermmy said it`s been my experience that that I`ve had to check and make adjustments to the grade up to 3 times. If you have a section that needs to be adjusted I`ve found it best to go back to the start of your grade and adjust it in the same direction you laid the track in. That way you know the point the grade is starting/measuring from is correct, and you may find that some are easier if you adjust the vertex height manually using the check vertex height and apply vertex height tools. I`ve found that sometimes track sections won`t change grade without changing the ones next to them.

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[Vern]

I find it easiest just to enter the gradient value in the appropriate field, which accepts positive or negative values, just prefix the number with a - sign for downhill. Apply to the new section just ahead of the spline connected to and sorted.

 

[Dermmy]

In...you may find that some are easier if you adjust the vertex height manually using the check vertex height and apply vertex height tools. I`ve found that sometimes track sections won`t change grade without changing the ones next to them.

Be wary of using 'Apply Height' on a grade, it permanently locks the vertex till changed manually. You cannot use 'Apply Grade' approaching a vertex which has a fixed height.

'Apply Height' is handy though for guaranteeing level track, or for fixing a required height at the top (or bottom) of a grade...

Andy

 

[dricketts]

Thanks guys. A lot of good info.

I didn't realize the effect of applying gradient nearest to the vertex. I'm sure that explains my undesired results.

I've discovered a prototype route has many grade variants like a roller coaster. Especially older routes from the 50's like the one I'm working on. I've been manually adjusting the spline vertex height to follow the DEM the best I can. At the same time I'm trying to keep the grade less than 1% neg or pos. I'm starting to think this route might have had sections greater than 1%.

It's the Frisco Highline in Southwest Mo.