QGIS – Fixing Empty Output in ShapeTools XY to Line Conversion

convertqgisqgis-plugins

I have a shapefile with 2 points.

I am using the XY to Line tool in the ShapeTools plugin to create a Geodesic, Great Circle, and Simple Line. However, in each case, the tool is running successfully, but producing empty outputs.

The following screenshots shows the parameters:

The straight line connecting the 2 points is getting successfully created if I use the Points to Path tool.

The aim of this exercise is to be able to see the difference in geodetic distance and Euclidean distance. I also want to show how the projection of the geodetic line connecting the two points look like on a flat map.

If I do not check the optional check boxes, Use the point geometry for the line starting point and Use the point geometry for the line ending point, the tool show the error Please select valid starting and ending point columns.

I am using QGIS 3.4.1

Best Answer

You seem to have checked both 'Use point geometry for the line starting/ending point'. However, this tool is meant to work with 1 feature > 1 line, not 2 features > 1 line. Try to include all the info (start/end x/y fields) in one single record per line that you want to create.

The tool help states the following : 'One of the coordinates can be from a point layer geometry', so you can only use a point geometry for one of the coordinates, and the other coordinate pair would have to be in 2 fields (x/y) in the table.

Related Solutions

[GIS] Splitting line at point positions using QGIS

QGIS won't do this natively to the best of my knowledge. However, you can use GRASS from within QGIS, and this thread looks like exactly what you want. I haven't tested this, but it all makes sense. Credit of course goes to the folks in that thread. First, you would import your data into GRASS then:

dump the coordinates to a text file (v.out.ascii) then loop thru that file, and feed the coords to v.edit, like so: v.out.ascii out=points.txt while read x y; do v.edit tool=break coord=$x,$y cat=0-99999 done < points.txt

Note the caveat that your points must be exactly on the line.

Or, even simpler in a bash environment:

v.out.ascii format=point in=pts --q | cut -d'|' -f1,2 | tr '|' ',' | while read COOR; do v.edit map=line tool=break coords=$COOR; done

ArcPy – Creating Lines from Points Pair Coordinates

This reads a table (Excel sheet in this case, but could be any table type) that looks like so:

enter image description here

S_X is start X point, E_X end X point, same for Y's. We iterate through the input table, then for each row, set the start/end X/Ys into a point, add that point to an array, then create a polyline from the array of two points. Then insert into the featureclass. Rinse and repeat.

import arcpy

in_rows = arcpy.SearchCursor(r"D:\Temp\Lines.xls\Sheet1$")

point = arcpy.Point()
array = arcpy.Array()

featureList = []
cursor = arcpy.InsertCursor(r"D:\Temp\Lines.shp")
feat = cursor.newRow()

for in_row in in_rows:
    # Set X and Y for start and end points
    point.X = in_row.S_X
    point.Y = in_row.S_Y
    array.add(point)
    point.X = in_row.E_X
    point.Y = in_row.E_Y
    array.add(point)   
    # Create a Polyline object based on the array of points
    polyline = arcpy.Polyline(array)
    # Clear the array for future use
    array.removeAll()
    # Append to the list of Polyline objects
    featureList.append(polyline)
    # Insert the feature
    feat.shape = polyline
    cursor.insertRow(feat)
del feat
del cursor

And you get your lines:

enter image description here

Best Answer

Related Solutions

[GIS] Splitting line at point positions using QGIS

ArcPy – Creating Lines from Points Pair Coordinates

Related Question