Create points at 50m intervals along line in EPSG:4326

Question

I have read multiple post on how to create points along the line. I have lines that represent routes. On this lines i would like to create point at the distance of 50m. I have tried different things:

QChainage Plugin
Geoalgorithims->Vector is the "Convert Lines to Points" option
and also GRASS module v.to.point

However, I do not get the desired output. I have been trying for a while. I must be missing something very basic.

When using the aforementioned techniques, I only get point at the start of my route and at the end. I would like to use a 50m interval between the points. I tried to specify that, but failed...

QUESTION

Am I using the right technique?
How do i specify the distance between the points?

score 3 · Answer 1 · answered Dec 02 '17 at 11:08

3

The GRASS v.to.points module should do what you want. The parameter "dmax" sets the (approximate)) distance between points.

What coordinate system is you line layer in? If it's longitude/latitude then the distance is degrees so you'll be adding points every 50 deg (~= 5000 km !)

answered Dec 02 '17 at 11:08

Micha

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My layer is in CRS: EPSG:4326, WGS 84. In project properties units for distance measurements are set to meter and coordinate display using is also map units(meters). But when I use 50m as distance, no points show up. Should I change the distance to degrees? In that case, how can i convert meters to degrees? (Sorry, i am actually not familiar geographical concepts) – user1607 Dec 02 '17 at 13:54
I would transform the layer to a meter based coordinate system altogether. The "coordinate display" is just that: only for display. In QGIS, you can use Save As.. to save the layer to a new shapefile, and choose a different (projected) coordinate system based on your location. – Micha Dec 03 '17 at 09:40
@Dana EPSG:4326 is lon,lat. You cannot (easily) do 50 m intervals in a coordinate system which is based on different units which have a non-linear mapping between degrees and meters. Convert your data into a meters-based coordinate system, split at 50 m intervals, and then convert back to EPSG:4326. – mankoff Dec 03 '17 at 10:28
@Micha thanks for your input. I have included an alternative answer, which from my point of view was simpler. Let me know what you think of that – user1607 Dec 03 '17 at 12:04
@mankoff also, I have overcome the going back and forth between CRS using the plugin Qchainage - see the answer below – user1607 Dec 03 '17 at 12:05

score 1 · Accepted Answer · answered Dec 03 '17 at 11:56

There is an alternative way how to convert lines to points at 50m interval, which I found somewhat more straight forward:

Convert the layer that contains your line to CRS: *CRS = Belge Lambert 1972, because this one is in meters.
download the plugin QChainage
go to vector|QChainage|QChainage. Notice, now we work with meters. Select the layer that you would like to convert to points. Set Chainage every 50m. Click on OK.

Doing these 3 steps you will convert your line to points at every 50m

Create points at 50m intervals along line in EPSG:4326

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