This came up this morning and Advanced Select takes care of this. While Non Zero Contours will be typically separated vertically from undefined contours in 3D and can be graphically selected in the 3D view, in some cases you may be working at near zero elevation in which case this option may not work, so then how do you do this.
- Select all of the contours
- Run the Advanced Select command
- Choose the Current selection option
- For Data Type - you can leave this set to Multiple Data Types or choose a specific type of line if you need to narrow down the selection to just polylines or CAD Lines or Linestrings etc.
- Select Data with the following property
- Select the Elevation Min option
- For “That is” select Greater than or equals
- Enter a value above zero and below the elevation of your 3D contours e.g. 0.1 or 1.0
- Check the Invert selected objects checkbox - this will pick the inverse of the above selection criteria from the currently selected objects i.e. the 2D lines
- Hit Apply
This should make the selection of the data that you require
Alternatively you can try the following as well
I assume that the contours are near 0 otherwise you could separate them by selection in 3D (undefined will be at 0 and the others will be at their elevation). You can still exaggerate the 3D view vertically to create a vertical separation between undefined and defined value contours - even if the first contour is at or close to zero.
You could also set the setting - do not display in 3D from the View Filter Display Options for the undefined Z contours, then you can isolate the layer, select all the contours in the plan view and then select the 3D contours again in the 3D view to deselect them (as the 2D contours would not be visible in the 3D view).
I noticed that for Polylines, I created 2x 2D undefined polylines and then polylines at 100, 101, 102, 103 elevations - and in 3D they all show up at about the same elevation which surprised me - but I found if I exaggerated the 3D view that they separated to the point where I could select them graphically