XY To Line - Line Type - GEODESIC vs NORMAL_SECTION

Question

When using the new XY To Line tool the Line Type is provided. However I cannot find anything regarding more detailed descriptions of the Line Type. What is the difference between GEODESIC and NORMAL_SECTION? Also, what are some examples as to when are the best instances to use which tool?

Type of two-point lines to construct. Default line type is GEODESIC.

GEODESIC???Straight line based on a spheroid. 
GREAT_CIRCLE???Straight line on a sphere. 
RHUMB_LINE???Line of constant bearing (direction). 
NORMAL_SECTION???Straight line on a spheroid.

DanielSheehan · Answer

update: used Jeff Jenness's tool - http://www.jennessent.com/

I'd appreciate it if someone at ESRI could explain how I can have the Shape_Length (not only the direction and angles of the line) portray spheroidic (?) distance.

DanielSheehan · Answer

Using this tool does the Shape_Length give you the distance proper distance? I want to give all four options of distance, so would I want to run this tool 4 times and join a distance field using a unique ID?

My concern is that when using a projection system I'll lose out on the distance accounting for curvature of the earth. So for example the distance of that line looking down from above at it is less than the actual distance in a 3D world. Should my measuring tool match the Shape_Length number?

Let me give you the scenario in greater detail, so I have 40,000 + address points all across the US (50 States) that are in some cases representing moves or non-moves or missing data intervals. 2/5 of the data I created at USA_Contiguous_Albers_Equal_Area_Conic geocoding, 3/5 of the data was done by someone else and all I have are their Lat Longs in WGS84 (and without geocoding documentation!!!). I have generated lines by bringing all the points to WGS84 creating lines, then projecting to USA_Contiguous_Albers_Equal_Area_Conic.

I have a pretty detailed ID scheme so that I've got it down cold how to tie one origin point to a destination point. And now my concern is that I'm creating these lines and calculating their distance in the correct way. So my questions are;

what is the best projection system to use to report distances across the US?;

how is the best way to make sure the distances incorporate curvature correctly?

is my Shape_Length field the value that I need to be using for distance?;

and am I using the right tool - my boss said he used to use a 3rd party tool to calculate distance incorporating curvature?

Thanks,
Danny

MelitaKennedy · Answer

When using the new XY To Line tool the Line Type is provided. However I cannot find anything regarding more detailed descriptions of the Line Type. What is the difference between GEODESIC and NORMAL_SECTION? Also, what are some examples as to when are the best instances to use which tool?

Type of two-point lines to construct. Default line type is GEODESIC.

GEODESIC�??Straight line based on a spheroid. 
GREAT_CIRCLE�??Straight line on a sphere. 
RHUMB_LINE�??Line of constant bearing (direction). 
NORMAL_SECTION�??Straight line on a spheroid.

Hi Daniel,

A normal section is a simplified version of a geodesic line. It's easier to construct, but won't quite be the shortest path. It is defined by the intersection of a plane that passes through two points on the surface of the spheroid and is perpendicular to the surface ('normal') at the first point.

Melita