[GIS] Calculating distance between two Linestring using Python

distancegeojsonlinestringpythonshapely

I have two linestring, each linestring represents a rail road. I am trying to calculate minimum distance between these two linestrings. Which function is efficient to do this?

I have only come across distance function that takes a point and linestring but not 2 linestring.

For e.g.:

l1 = LineString([(42.073407, -87.806245), (42.0752508,-87.8080299)])  
l2 = LINESTRING(35.442827 -79.470579, 35.444889 -79.469465, 35.445829 -79.468907, 35.446608 -79.468294, 35.447893 -79.46687)

I need the distance between these two shapely objects.

Best Answer

In The Shapely User Manual -> object.distance(other)

Returns the minimum distance (float) to the other geometric object.

from shapely.geometry import LineString
l1 = LineString([(42.073407, -87.806245), (42.0752508,-87.8080299)])
from shapely.wkt import loads
l2 = loads(" LINESTRING(35.442827 -79.470579, 35.444889 -79.469465, 35.445829 -79.468907, 35.446608 -79.468294, 35.447893 -79.46687)")
l1.distance(l2)
10.650628707489625
l2.distance(l1)
10.650628707489625

Related Solutions

[GIS] How to calculate the “depth” of a linestring using postgis

Consider some test data similar top the thick line in the question's figure:

SELECT 'LINESTRING (114 374, 200 380, 250 350, 259 343, 350 280, 380 180, 383 169, 360 80)'::geometry AS geom
INTO TEMP data;

the straight line (dashed) can be constructed from the start and end points:

SELECT ST_AsText(ST_MakeLine(ST_StartPoint(geom), ST_EndPoint(geom)))
FROM data;

         st_astext
----------------------------
 LINESTRING(114 374,360 80)
(1 row)

Distances from each vertex (coordinate) can then be found to the straight line:

SELECT ST_Distance((ST_DumpPoints(geom)).geom, ST_MakeLine(ST_StartPoint(geom), ST_EndPoint(geom)))
FROM data
GROUP BY geom;

   st_distance
------------------
                0
  69.806901017674
 88.9020622825982
 91.3124350980067
  120.67515848571
 79.5109993654224
 74.7528608207199
                0
(8 rows)

All of this logic can be put into a nested query to get the maximum depth from the geometry:

SELECT geom, max(depth)
FROM (
  SELECT geom, ST_Distance((ST_DumpPoints(geom)).geom, ST_MakeLine(ST_StartPoint(geom), ST_EndPoint(geom))) AS depth
  FROM data
  GROUP BY geom
) AS f
GROUP BY geom;

which is 120.67515848571 for this example.

[GIS] Calculate distance between point and linestring and how to represent that on QGIS

You could use the Distance to nearest hub algorithm from the Processing plugin which you could add your points and your lines layer instead of going through a query.

Distance to nearest hub

From a couple of example layers that I have, you can get something like this:

Output player for Distance to nearest hub analysis

Then when you open up the Attributes Table for the output layer, you will be given the HubName and HubDist in whatever measurement scale you selected (in my case, meters). Hope this helps.

Best Answer

Related Solutions

[GIS] How to calculate the “depth” of a linestring using postgis

[GIS] Calculate distance between point and linestring and how to represent that on QGIS

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