Distance calculation including slope - Spatial Analyst

[PeterMullin]

Hello,

i would like to calculate the nearest distance (Euclidean Distance) with the Spatial Analyst Extension. Calculating only the distance is no problem. However, I would like to include the slope as it has strong influence on the real distance.
I have on layer which provides the heigt. And in an other layer I have the slope. Finally I have an layer with the locations from where the shortest distance including the elevation should be measured.
Anyone could help me, please.
Thx
P

[PeterMullin]

Dear Bill,

well I want to measure the distance between A and B. A and B lies a few 100 km away from each other as the bird flys. If this would be only a plane I could use the distance tool in the spatial analyst. But there are some mountains in between. Going up and down a mountain is longer than a straight line.
Example I want to know how long must be a road from A to B. Than I need to know this.

Thx

[LukeHutchinson]

I have a set of arcs that I've converted to 3d.  I now need to recalculate the lengths of these lines, since the 2d length will vary from the 3d length.  I cannot find a way to do this, any help would be greatly appreciated.

[EricRice]

I have a set of arcs that I've converted to 3d.  I now need to recalculate the lengths of these lines, since the 2d length will vary from the 3d length.  I cannot find a way to do this, any help would be greatly appreciated.

Technically you didn't need to convert your arcs into 3d.  The Surface Length tool densifies the line at a user defined interval, or by default, the sampling distance is the natural densification of a TIN or the cell size of a raster.  This tool only applies to 9.3.1 and prior.  The input line features should be 2d.

In ArcGIS 10 there is an enhanced tool, Add Surface Information, which is the replacement for Surface Length.

Surface Length
http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//00q90000000z000000.htm

How Surface Length works (detailed)
http://webhelp.esri.com/arcgisdesktop/9.3/index.cfm?TopicName=How Surface Length (3D Analyst) works

Add Surface Information
http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//00q900000016000000.htm

Also in ArcGIS 10 is a new 3d length option in the Calculate Geometry tool. e.g. Right click on field > Calculate Geometry.