1
vote
1answer
11 views

Close linestring to linering in PostGis

is there a function which closes a linestring to a linering? I couldn't found such a function in the documentation. Thanks.
2
votes
1answer
69 views

PostGIS - How do I create a line that directly connects two earth points without travelling over a geodesic?

In PostGIS 2.1.1, I've noticed that if I create two distant earth points with equal altitude and then create a line connecting them, as I gather interpolated Z coordinate data along the line my Z ...
2
votes
1answer
114 views

Using ST_split to split a line feature using nearby points

I have a line shapefile and a point shapefile, and the line has just one segment and its attribute table, the point shapefile has points near the line above, not on it and the close ...
0
votes
1answer
40 views

Switch line direction for PostGIS-lines in QGIS or Pgadmin

I am trying to switch the line direction in a PostGIS-layer. The postgis-geometry column is e.g. "LINESTRING(0 0, 1 1, 2 1, 2 2)". The reason is that my symbology is direction-dependent, but I drew ...
0
votes
2answers
54 views

sql query to get origins and destinations

I have a table of cities with an ID and geometry (200K rows) and a table of travels, with only two ID: idfrom, idto (7K rows) I'm wondering how could I select the geometries for each one in order to ...
3
votes
1answer
135 views

How can I move along a line (or path)?

Given a line (street, railroad, river...) I want to simulate a moviment inside this line. Example: See this picture: Say I'm in "Nagqu" and want to move to "Kunlunqial". In a time (t=0) I'm in ...
1
vote
0answers
197 views

Smoothing Lines in PostGIS

I want to smooth Lines in postgis, to be more specific, I want to smooth road data from OpenStreetMap. Basicly I thought of something like this scenario. This would be a possible road segment. I ...
2
votes
1answer
100 views

Draw a line and a buffer around it onto the spheroid

I need to draw a line between two points and create a buffer around this line. The only difficulty is that I need to draw not a "cartesian" line but a line that is laying on the spheroid. I tried to ...
1
vote
1answer
850 views

PostGIS, create line from points

I have a PostGIS table with position data of numerous vehicles and want to create lines from these points. Data can be selected by vehicle id and ordered by timestamp but how to create lines from the ...
-1
votes
1answer
311 views

QGIS and Python - create line with multiple points in postgis [closed]

How can I create a line, with Python functions, with many points that are records in Postgis? Thank you
14
votes
2answers
1k views

How can I merge/collapse nearby and parallel road lines (eg. a dual-carriageway) into one single line?

I have a shapefile from OSM which contains all the roads within a city. Larger roads (like dual-carriageways) seem to have 2 parallel lines. I'd like to collapse / combine those into 1 line so I can ...
3
votes
1answer
329 views

How to connect particular sets of points with (poly)lines?

I think my problem is quite easy to be solved by the most postgis-users, but i am a bloody beginner: i have a timestamped point-table representing GPS-tracked places of different cars. To distinguish ...
1
vote
4answers
649 views

How to find the center point of MULTILINESTRING?

How to find the center point of MULTILINESTRING, which lies on the multiline?
5
votes
1answer
194 views

Given 2 LINESTRINGs with common point, how to extract common point?

I have 2 LINESTRING geometries. I know both share a common point. Using PostGIS for Postgres, what is the cleanest way to extract the common point? Example with illustration: How do I extract the ...
6
votes
1answer
521 views

Filling a polygon with lines using Postgis

i need to calculate a specific distance in an area. The distance is calculated from parallel lines in a polygon, And i need to find out how many parallel lines (with x meters distance to each other) ...