topic Re: Why integer Z values for Interpolate Line? in 3D Questions

Why integer Z values for Interpolate Line?

SeanBemis — Thu, 31 Mar 2011 16:59:14 GMT

ArcGIS 9.3.1, Service Pack 2

While working with my LiDAR data, I occasionally like to create a series of topographic profiles using the interpolate line tool in 3D analyst to explore landforms, compare elevations and such. However, recently when using the interpolate line tool, the profile graph comes out with integer elevation values. If I right-click and check the actual data in the profile graph's properties, it is in fact in integers. However, I have repeatedly verified that the DEM I am extracting the profile from is a floating point grid (min/max values have decimal point values, properties say it is 32-bit floating point data, slope map derived from the DEM looks great - not steppy like an integer grid would be).

I have not been able to uncover any settings/options that would affect this problem - anyone out there have any ideas? Why might this have just started recently? I don't see ET Geowizards as a alternative to an actual solution for this problem - when exploring data and topographic relationships, the 3-click ability to rapidly create profile graphs through 3d Analyst is needed.

thanks for any ideas out there,

Re: Why integer Z values for Interpolate Line?

JacquelineDiaz_Nieto — Thu, 30 Jun 2011 17:54:10 GMT

This is very strange. The exact same thing happened to me in the same ArcGIS session. I was using the Create Profile tool and it was creating correct profiles with the decimal points from the DEM. Then all of a sudden it changed to just outputting the elevations as integers - hence I was getting stepped profiles. As far as I'm aware I didn't change anything!
Then I thought I've have a go at exporting my DEM outside of the file geodtabase and also the polylines to a shapefile (instead of working with data insde a gdb) and now it works again - I'm getting the output of the profile with th decimals. Very strange but at least it worked.

Re: Why integer Z values for Interpolate Line?

JeffreySwain — Fri, 01 Jul 2011 10:22:03 GMT

So the original raster was in a file geodatabase, but works outside of a geodatabase? Is it still reproducible or just in that particular ArcMap session?

Re: Why integer Z values for Interpolate Line?

SeanBemis — Tue, 22 Dec 2015 03:42:53 GMT

Wow - I found myself having the same problem again! This time in 10.3.1. I thought it was a source data issue until I used the Identify tool to examine the cell values and found that they are floating point values. Without any particularly compelling solutions to this issue in the forum, but I tried changing the projection as someone else had, and it resolved the issue here. For whatever reason, simply switching the coordinate system for the map document from UTM NAD 83 to UTM WGS 84 allow the Interpolate Line --> Profile Graph function to output a graph with floating point values on the y-axis.

Anyone know why this is happening?

Re: Why integer Z values for Interpolate Line?

RebeccaRichman — Thu, 31 Dec 2015 19:27:29 GMT

It looks like this is a known bug:

NIM063478: 3D Analyst Toolbar Interpolate Line tool rounds z values.