topic Re: Trying to Convert Points to a Polyline in Geoprocessing Questions

Trying to Convert Points to a Polyline

MATTHEWTOMITZ — Fri, 13 Apr 2018 19:20:51 GMT

Hello everyone. I have an issue with converting points into a polyline. I have trail lines, and elevation points. I am trying to combine the two so that I have a nice polyline with slope values representing gentle-moderate-steep.

When I run Point-to-Polyline, I get weird zigzag lines that DO go from point to point, but also go out of order. I've run XY to line, but only get one XY value for the whole line. I tried Split Line at Point, which made a polyline of only two segments (when I'm looking for a couple hundred segments).

I don't know what I'm missing, but I just want to make a simple sequential polyline that runs through the order of points and generates a smooth trail with slope visuals.

Can someone please tell me what I'm missing?

Re: Trying to Convert Points to a Polyline

DanPatterson_Retired — Fri, 13 Apr 2018 19:23:54 GMT

Were the points in the actual order or did you sort them? sorting doesn't work BTW, they have to be sequential.

Maybe a short sequence of points to make sure that X and Y haven't been switched or Z isn't being plotted against X or Y.

Re: Trying to Convert Points to a Polyline

MATTHEWTOMITZ — Fri, 13 Apr 2018 19:33:29 GMT

The points have no ordering themselves, they were generated by Raster to Point. They are positioned in such a way that they follow the trail. Is there some way I can add a sequence of numbers? I will have a couple thousand points, so manual would take a long, long time.

Re: Trying to Convert Points to a Polyline

DanPatterson_Retired — Fri, 13 Apr 2018 19:44:09 GMT

could you not use http://pro.arcgis.com/en/pro-app/tool-reference/spatial-analyst/extract-by-points.htm

assuming your points were in sequential order.

There is no way to order points in some sort of order unless you can provide the rule for the sort... then anything is possible.

Re: Trying to Convert Points to a Polyline

MATTHEWTOMITZ — Fri, 13 Apr 2018 20:05:59 GMT

The points are in a line, so a sequence can be inferred. They don't have a field that gives a good sequencing. They have ObjectID codes, but the numbers jump around through the several thousand points, so point 1 could be next to point 3759. The Extract by Points tool asks for XY coordinates for every point, and doesn't seem very tenable to my limited experience.

Re: Trying to Convert Points to a Polyline

DanPatterson_Retired — Fri, 13 Apr 2018 20:11:47 GMT

I have had success reordering points using a lexicographic or radial sort... the ability to do so easily depends on how snakey the line is. If the line folds back on itself then sorting isn't going to work. Maybe construct a line manually, densify it, segment it and see if you can get the points to snap to it using a spatial join. It sounds worse that it really is

Re: Trying to Convert Points to a Polyline

MATTHEWTOMITZ — Sat, 14 Apr 2018 21:55:48 GMT

I do have some trails that don't make an easy line, they do curve on themselves or have splits. And yeah, that does sound a bit confusing. To be clear, I should:

Make a line shapefile, use Editor to draw lines of the trails.

Use a Density (?) tool

Segment the line, I guess into polylines

Spatially join the points to the line

I think that's not so bad, I'll try it.

Re: Trying to Convert Points to a Polyline

DanPatterson_Retired — Sat, 14 Apr 2018 23:48:54 GMT

Densify... not Density.

Yes, draw the polyline as best you can... Densify the line, And I am hoping you have an Advanced license

because you have to split the lines at the vertices http://desktop.arcgis.com/en/arcmap/latest/tools/data-management-toolbox/split-line-at-vertices.htm

or at least a standard license so you can snap your points to the line http://desktop.arcgis.com/en/arcmap/latest/tools/editing-toolbox/snap.htm

otherwise it will be some searchcursor thing