Z factor in ASCII 3D to Feature Class

[LeighHolcombe]

I have a very large XYZ file of bathymetric soundings. X is longitude in decimal degrees, Y is latitude in decimal degrees, and Z is negative meters. Coordinates are in WGS84.
Sample record:
-86.23 21.45 -125.67

I want to eventually turn these points into a TIN. I am able to create a 3D feature class with a Z factor of 1 (default), but after turning the FC into a TIN, I get a vertical exaggeration error when opening the TIN in ArcScene. Calculating the exaggeration from extent yields a number like 0.00000009. Do I need use a Z factor to convert the meter depths into some miniscule portion of a degree? Isn't the number of meters in a degree dependent on latitude? What is an appropriate Z factor here?

Thanks

[JieChang]

http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//009z000000vm000000.htm

- Jie

[LeighHolcombe]

Thank you, that's exactly what I needed.

[EricRice]

Leigh,

I'm sorry, but that is not what you want to do.  You may be able to visualize your TIN by setting a vertical exaggeration to a small number, but the validity of your surface is compromised from the beginning because you built it using data in a GCS.   Delaunay triangulations are not valid when constructed using angular coordinates from geographic coordinate systems.  A TIN should be constructed from data in feet, meters, not decimal degrees.

What is a TIN surface?

Please project your point data into something that uses meters (since your z is in meters), like UTM, Albers, etc... Then reconstruct your TIN.  When x,y,z are all in meters you don't have to worry about z factor.  It will be 1.  If the surface is flat relative to its extent, you can use vertical exaggeration to show more relief. Perhaps a value of 2.5 or something.

About Vertical Exaggeration

Best Regards,
Eric

[LeighHolcombe]

Thanks, Eric, I'll give that a go.