Sort list of GPS waypoints by both Lat and Long, not by Lat then Long.

**CarolinaJim** · 09-22-2012, 02:15 PM

First I'd like to introduce myself, my name is Jim and I'm an avid fisherman.

I want to sort GPS waypoints based on both Latitude and longitude and can not figure out how to make this work. Any help would be greatly appreciated.

Image 4 lakes arranged like this geographically (below). Lakes 1 and 2 occupy the same Lats N to S, Lakes 3 and 4 occupy the same Lats N to S, lakes 1 and 3 occupy the same Longs E to W, and lakes 2 and 4 occupy the same Longs E to W.Also, imagine that each lake had 3 waypoints in the exact center E to W and 1 at the Norther most point, 1 in the middle N to S,and 1 at the Southern most point of the lake.

Lake1 Lake2
Lake3 Lake4

I want my sort to end up like this.
Lake4 waypoints
Lake3 waypoints
Lake2 waypoints
Lake1 waypoints

This is some test data, I really do not have the lake name or consistent waypoint naming to start with (thought it would be helpful for testing) I can only rely on having to sorting by lat and long.

Lat Long Lake waypoint name
28 00 00.0 80 00 00.0 Lake 1 1
27 00 00.0 80 00 00.0 Lake 1 2
26 00 00.0 80 00 00.0 Lake 1 3
28 00 00.0 78 00 00.0 Lake 2 4
27 00 00.0 78 00 00.0 Lake 2 5
26 00 00.0 78 00 00.0 Lake 2 6
25 00 00.0 80 00 00.0 Lake 3 7
24 00 00.0 80 00 00.0 Lake 3 8
23 00 00.0 80 00 00.0 Lake 3 9
25 00 00.0 78 00 00.0 Lake 4 10
24 00 00.0 78 00 00.0 Lake 4 11
23 00 00.0 78 00 00.0 Lake 4 12

**shg** · 09-22-2012, 02:22 PM

I don't think you can do better than to annotate each point and sort by that:

Lake Bob Wpt 1
Lake Bob Wpt 2
Lake Bob Wpt 3

Lake Joe Wpt 1
Lake Joe Wpt 2
Lake Joe Wpt 3

**CarolinaJim** · 09-22-2012, 02:26 PM

That is what I do now, and it is laborious. I was hoping someone had a formula for x,y comparing that produced the desired grouping.

Thanks,
Jim

**shg** · 09-22-2012, 02:32 PM

There are lots of algorithms for connecting random points (Google delaunay triangulation, for example); none are trivial, and I'm not sure what the value of the end result would be.

You could subivide the points into, say, a 3 x 3 grid (Top-Left, Top-Center, Top-Right ...), and sort by grid coordinate, but I don't see how that would help keep relevant data together.

EDIT: Plotting the points would give a visual aid to the annotation.

**MrShorty** · 09-22-2012, 04:21 PM

I'm not sure how one would implement this in Excel (as shg says, I doubt it is a trivial algorithm to put in), but the way I use to do this with a free GPS waypoint program called EasyGPS went something like this:

Select a reference waypoint.
Calculate bearing and distance for each waypoint from the reference waypoint (the program I had did these calculations automatically. I'm sure Excel could be programmed to calculate these values, and I'm pretty sure the algorithms have been discussed here before).)
Then you can "sort" your waypoints based on bearing and distance from the reference waypoint. If your reference waypoint is reasonably well selected, then the points associated with each lake should cluster together.