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Question

Extract line segments between two points

M
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Hi

I have a spreadsheet (see table below) with a start and end point coordinates for different road sections and I'm trying to extract the road segments between the start and end points from another dataset containing my road geometry. Unfortunately the start and end points do not always lie on the road so I would need to snap it to the closest road. The road directions (road ways) are stored as separate features in the dataset with a common road id.

Section IdStart LatStart LongEnd LatEnd LongA-33.938..., 151.151.-33.935...151.131...B-33.949...151.138..-33.931...151.154...C------------

E.g. For Section B, I want to extract the two segments in green from the underlying blue road. The eastbound (EB) and westbound (WB) road features have a common road id of 1.

I tried using two vertex creators, a point on line over layer, a topology builder and feature merger, but I haven't had too much success.

Any ideas on how this could be achieved?

10 replies

M
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@jeroenstiers I haven't been able to get the point on line overlayer to work correctly. I'm not sure what I'm missing.

takashi
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Userlevel 3
Badge +17

If each line can be spatially related to just 2 points (start point and end point belonging to the same section), this data flow might work.

takashi
Rank
Userlevel 3
Badge +17

@jeroenstiers I haven't been able to get the point on line overlayer to work correctly. I'm not sure what I'm missing.

Because the PointOnLineOverlayer doesn't snap the end nodes of split lines to the input points, the output lines and points may not construct a network topology.

J
Badge +7

Hi mkov,

I found a method that works for 2 points and 1 road. So it should work for the road with ID 2 and also for one segment for the road with ID 1.

I tried this using created a sample. Can you try this method on your data to see if it works?

I am not entirely sure the 'select only 1 segment'-part is the most efficient one but it works :)

FME Inspector:

FME Workbench:

J
Badge +7

Hi mkov,

I found a method that works for 2 points and 1 road. So it should work for the road with ID 2 and also for one segment for the road with ID 1.

I tried this using created a sample. Can you try this method on your data to see if it works?

I am not entirely sure the 'select only 1 segment'-part is the most efficient one but it works :)

FME Inspector:

FME Workbench:

The segmentID used in the FeatureMerger is created in the Counter.

J
Badge +7

If each line can be spatially related to just 2 points (start point and end point belonging to the same section), this data flow might work.

I implemented this method to find out how it works but I cannot find out what should happen with the MeasureExtractor:2 in combination with the StatisticsCalculator since the attribute '_point_measure' is empty when testing with my testdata.

Could you confirm if the result of the MeasureExtractor:2 should be the following?

 

For every point, the _point_measure should be the location of this point on the line. By calculating the mean of these two values, you make sure the result is a value between those two locations. That is why you can use this information in the Tester. Is this correct?
takashi
Rank
Userlevel 3
Badge +17

If each line can be spatially related to just 2 points (start point and end point belonging to the same section), this data flow might work.

Completely different approach flashed. Assuming that each line can be split into three parts by a pair of two points representing a section, the middle part is the required one.

1. Once connect the three parts with the LineJoiner.

  • Group By: <line ID attribute>
  • Preserve Original Orientation: yes
  • List Name: _list
  • Preserve Lines as Path Segments: Yes

2. Split the resulting line (path) into three parts again, with the PathSplitter.

  • Segment Number Attribute: _segment_number
  • List Attribute: _list{}

The segment having 1 as "_segment_number" is the middle segment.

takashi
Rank
Userlevel 3
Badge +17

I implemented this method to find out how it works but I cannot find out what should happen with the MeasureExtractor:2 in combination with the StatisticsCalculator since the attribute '_point_measure' is empty when testing with my testdata.

Could you confirm if the result of the MeasureExtractor:2 should be the following?

 

For every point, the _point_measure should be the location of this point on the line. By calculating the mean of these two values, you make sure the result is a value between those two locations. That is why you can use this information in the Tester. Is this correct?

The ability to set measure to points of the PointOnLineOverlayer is relatively new (maybe FME 2015.1+?). Which version of FME are you using?.

J
Badge +7

The ability to set measure to points of the PointOnLineOverlayer is relatively new (maybe FME 2015.1+?). Which version of FME are you using?.

I was working in build 15250 and it didn't work. In build 15482 it does.

Thank you!

G
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Because the PointOnLineOverlayer doesn't snap the end nodes of split lines to the input points, the output lines and points may not construct a network topology.

Many Thanks @takashi this method works for me doing a similar process to the original question. Best regards Steve

 

 

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