Here's what's happening:

I want to create a 3D line using only the height of some GSP points. I need to be able to extrapolate the vertice's height between where it's known to the one where it's unkonwn.

What I have tried:

  • Creating a TIN from GPS points: where the line meanders and there is no GPS points, the height is not correct.
  • Linear Referencing tools: but as originally the Polyline Z has no value interpolated between each vertex, it doesn't seem to do what is needed
  • Conversion of Point to raster at a 1 m cell (Nodata outside the cell where the GPS points lay) and extraction of the Z value to the vertex where they overlap the cell with value, leaving the not-overlapping vertices without Z value.

Is this what I need?:

I think I should use something like "IZ.InterpolateZsBetween" but I am useless at coding. Could someone please explain me how to implement this fonction?

Many thanks

  • not usnderstanding your data. you say line meanders no gps points. how can the line meander if there is no point. I don't think you can do any extrapolation without a surface. DEM, TIN or otherwise. Also consider getting Z on a line you must specify what points you want z for (measured distance, equal division or vertices).
    – Brad Nesom
    Commented Sep 3, 2013 at 13:49
  • I am working on hydaulik modelling and starting at it. River center lines and river banks are drawn from aerial pictures and adjusted with GPS points, hence giving the Z value at only specific vertex. The center line and the bank lines are meandering and the GPS point are recorded irregurlarly (only at bridges intersections), therefore an extrapolation along the line of the Z value of vertex is required.
    – PMessager
    Commented Sep 4, 2013 at 9:31

1 Answer 1


IZ.InterpolateZsBetween interpolates between vertices with Z value. Use it if your polyline has some Z values.

Otherwise you can use Extract Values to points or Interpolate Shape. These both require surface that you may get your values. Not sure if TIN would be ok, but always you can convert TIN To Raster.

Also you could construct polyline ZM and Calibrate Route M with your GPS points. It should do what IZ.InterpolateZsBetween, only for M. Than you could use M as Z. though as far as I remember year back there was a bug in this algorithm. Still worth a try.

  • This is a good idea, swapping the M for the Z, worth to give a try indead. Thanks for the suggestion.
    – PMessager
    Commented Sep 4, 2013 at 9:34

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