# Elevation Difference Between Linestring

If I have two intersecting linestring. How can I check the delta between the two elevated lines? Does RPS have such a tool or another check to get the delta?

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Four options here - none are the most obvious but all work

1. If the lines only cross 1x then you can make a surface of the two lines, you will get a Flag at the intersection point, look at the Flags Pane and it will tell you the elevation difference at the crossing point

2. If you break both lines at the crossing point you can measure the distance between the end of the higher line at the intersection and the end of the lower line at the crossing point.

3. If you use Explore Object and use one of the two lines as a reference line and the second line as the line to explore and then snap to the intersection of the two lines, it will tell you the elevation of the two lines at the crossing point - you can then subtract the difference between the two lines

4. If you edit both lines and add a VPI at the intersection point, show the line markings you can then measure between the two VPIs and get the vertical distance in the 3D View

Alan

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number 4. I believe you can use the intersection snap and avoid added vpiâ€™s and the visual noise that show line markings will add

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I donâ€™t think you can use intersection because TBC snaps are only 3D when there is a single solution i.e. if two lines cross at elevation 110 an intersection snap will pick XY of the Intersection and the elevation 110 because there is only one answer.

If two lines cross with one line at 110 and the other at 100, there are two Intersection options, and you TBC will always compute the elevation on the line with the lowest object serial number (not the lowest or the highest specifically) - so it creates the XY OK but only computes the Z of one of the two potential intersections. So when you pick the intersection a second time it picks the same XYZ and computes a 0 Slope / Vertical Distance as a result. However you can see in 3D which point it picked and then use the Perpendicular trick below to compute the vertical / slope distance

I have not found any way to compute this using an Intersection snap.

Also because the Distance Measure Tool only asks you for a From and To location and doesnâ€™t separate out the Elevation as a data entry item, you cannot compute an XY and then add a separate Z for each of the From and To points to compute the vertical separation. You also cannot snap along line snap to compute the Z either for the same reason.

However you can do the following

You can for the From location pick the intersection point and that will always pick the elevation from the first object in the database (you can see in 3D view which location it picked on which line), then if you select Perpendicular Snap from the right click menu for the To location and click the second line it will compute you the slope distance which is actually vertical. Note that TBC shows Red Triangle warnings if you pick the From Location in Plan View and the second line for the Perpendicular snap in the 3D view - it seems that both have to be selected in the Plan View for this to work currently

I think there are some bugs in here that could be fixed and will forward to Trimble to look at

Alan

i gave only half of my solution i suppose. And i donâ€™t do it often enough to be emphatic that it is consistent.

From Plan view select the intersection using the snap or right click and choose the intersection snap, switching to 3D view use the line snap to grab the line above. As stated it is typically going to grab the vert below and the line snap will allow for grabbing the line above. I did this ten times and it worked eight. I do get the slightest horizontal shift so it is not directly above/below - it is probably quicker to add two VPIs along the lines which would ready snap and be more in line with the solution for the question posed. My vote stays on option 4 regardless of the route getting there.

edit: I have played with this some more along some different lines and the horizontal shift is going to be dependent on the next available vpi along the line. so while initially I was seeing very small horizontal shifts, using other lines, I am getting much greater horizontal movement. it just happened that the initial set I was using had a vpi at crossing and the line above had a vpi within 0.008. Hence the ever so slight offset. Another avenue is to create two points along each line at the crossing and elevate to the line using the crossing. its almost the same amount of clicking and is independent of the line data. I donâ€™t particularly like to add stuff for the sake of stuff to my lines but that is just me being odd.

well, if we only had a explorer object with a reference line. one that would give the station and elevation of the master line and possibly a station and elevation from the reference lines. if only, i will give one of those a try.
thank you fellas.

i just had one of those wild hairsâ€¦ I just did a create linestring > zoomed in and used the right click line option to create a line from the two lines that crossâ€¦ then you can do a undo to remove the line or a quick delete. this will at least show the elevations. using the right click line option when doing a measure works also and a quick answer on the V. distance.

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