nav[aria-label="Primary Navigation"] { padding: 0; & ul { list-style: none; width: 100%; display: flex; flex-direction: row; justify-content: start; align-items: start; gap: 30px; padding: 0; & li { margin: 0; } & ul li { list-style: none; } } }

Create point shapefile at center of polyline WITH attributes from the polyline

MichaelJohnson1

Hi, can anyone tell me how to create a point at the center of a polyline and extract three attributes from the polyline to populate the point shapefile? I have polylines representing electrical conductors - I need to create a point at the center of each polyline as well as transfer length and conductor size attributes from the polyline to the point feature in the center. Much thanks for any help.

Find more posts tagged with

Accepted answers

DanPatterson_Retired

I should firstly point out, that if you simply add X,Y coordinates into your polyline shapefile's table, you can export the table (from the open table, save to dBase or whatever), THEN reload the table back into ArcMap as an event layer (File, Add Data, Add XY data), then save it out to a new shapefile. Time taken to do this is about 2-3 minutes max.

On with the explanations and comments

Given you are working with shapefiles and not true curves with the potential errors that Richard pointed out, then you should be able to create the table via several ways...

1 The one that Mark pointed out using the existing tools

2 Add two fields and use the Calculate Geometry to calculate the X and Y midpoint for each line segment (the 50% point which is 0.5 on the scale of 0-1.0

3 Add two fields and use the following python expressions for the 50% points ...or more flexibly ... any position or percentage along the line, using one of the sets of python field calculator expressions assuming your shapefield is named !Shape! . NOTE you have to use the Python parser in the field calculator.

So for percentages along the line you use values in the 0.0 to 1.0 range, hence 50% is actually 0.5 (I don't know why they don't call this fractional distance) and you set the other option to True

For actual distance along the line, then you specify the actual distances. IF ANY of the values exceed the acceptable range in EITHER case, then the coordinates are placed at the BEGINNING of the line.

So... for actual distance traverse

!Shape!.positionAlongLine(5000,False).centroid.X  #   5000m along a polyline X coordinate
!Shape!.positionAlongLine(5000,False).centroid.Y  #   5000m along a polyline Ycoordinate

For percentage distance traverse

!Shape!.positionAlongLine(0.5,True).centroid.X  #for polylines  use decimal % 0.25 = 25%
!Shape!.positionAlongLine(0.5,True).centroid.Y  #for polylines

Probably doesn't answer your question but it is worth looking into. By the way see the attached figure.

CalculatingPositionAlongLineExample.png

All comments

MarkBockenhauer

You could try the feature to point tool in toolbox.

ArcGIS Desktop

Check the inside (optional) check box. It will put the point at the centroid of the line, with all field attributes from the line.

RichardFairhurst

What Mark says is true for densified lines, but not for polylines containing true curves in a geodatabase. The inside point will usually be placed at the starting point of the line if it contains a true curve, not at the line centroid. True curves have to be densified to make the point locate itself at the center of the line. One option is to convert to a shapefile from a geodatabase to do that.

DanPatterson_Retired

does this statement not apply then? "For an input line: the output point will be on the line. If the line is a parametric (true) curve, the output point will be at the midpoint of the line." from the help file. For shapefiles it is not relevant since they aren't supported in the first place

RichardFairhurst

That statement is not true. I spent a day with Tech support on this issue and demonstrated that the inside option never put the point on the true curve center. It only puts the point at the ends of the true curve when the inside option is checked (at least if the line is only a true curve, which was what I was working with since the lines in my routine all came from the outlines of point buffers) or at the centroid that is not on the line if it is not checked. The point is only placed at the center of the polyline if the lines are densified. Converting to a shapefile was tech support's recommendation as a workaround.

DanPatterson_Retired

On with the explanations and comments

Given you are working with shapefiles and not true curves with the potential errors that Richard pointed out, then you should be able to create the table via several ways...

1 The one that Mark pointed out using the existing tools

2 Add two fields and use the Calculate Geometry to calculate the X and Y midpoint for each line segment (the 50% point which is 0.5 on the scale of 0-1.0

So... for actual distance traverse

!Shape!.positionAlongLine(5000,False).centroid.X  #   5000m along a polyline X coordinate
!Shape!.positionAlongLine(5000,False).centroid.Y  #   5000m along a polyline Ycoordinate

For percentage distance traverse

!Shape!.positionAlongLine(0.5,True).centroid.X  #for polylines  use decimal % 0.25 = 25%
!Shape!.positionAlongLine(0.5,True).centroid.Y  #for polylines

Probably doesn't answer your question but it is worth looking into. By the way see the attached figure.

CalculatingPositionAlongLineExample.png

MichaelJohnson1

Thanks to all for your answers and suggestions. I will try each of them and see what happens.

Much appreciation.

DanPatterson_Retired

let us know if it worked out for you

GISAdministrator_LMCC_0-1746663271608.png

ShengdiZhang_0-1746669792440.png

ShengdiZhang_1-1746669800526.jpeg

Join the Conversation

Signed in members can post, follow updates, and more. New here? Register a free account.

Quick Links

Community Help
Find useful guides, FAQs, and documents to help you navigate and make the most of Esri Community.