# How does a geocoder "know" which end of a line is the "to" and "from" ends?

Latest reply on Oct 2, 2019 by rborchert

This is sort-of a follow-up to my question yesterday.

Let's say I have a street line. I drew it from left to right. That is, if it has 2 nodes, node #1 will be on the left and node #2 will be on the right.

I then have FromLeft, FromRight, ToLeft and ToRight fields.

Even though I drew it from left to right, the flow of the addresses is right to left. So, for the fields I would put something like:

FromLeft: 1

FromRight: 2

ToLeft: 9

ToRight: 10

So the *actual* arrangement of the line would be:

10          2

-------------

9           1

Let's say a user uses my geocoder and enters an address of 3. 3 "should" be below the line a little to the left of the 1.

However, since I drew my line from left to right, will the geocoder "think" the 3 should be above the line a little bit to the right of the 10? After all, there's nothing that says the "right" or "left" of the line should be "above" it or "below" it in my scheme. It's just a line containing two nodes, and some numbers associated with it.

In other words, does the order of the nodes determine the direction of the flow of addresses (and thus, the right/left sides of the line), or does it figure that out some other way? Will I always have to draw my line in the direction of the flow of addresses (or alternatively, make the "to" and "from" and "right" and "left" numbers "backwards")?