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Note: Executed on QGIS 2.18

In my case, I can suggest several approaches that helped me to overcome an empty output after the execution of v.net.iso.

1. A really trivial and simple one. However, substituting a point layer with an absolutely new shapefile did the work. Even the previous one was correctly snapped. Additionally, the snapping of a new layer to vertexes is necessary. I replaced it after I have "cleaned" my polylines.

2. As was already mentioned by @muri, the implementation of v.clean geoalgorithm makes a tremendous impact.

I made a small graphical model which helped to refine the road network, see the image below. The core logic: bpol > rmdupl > snap > break > rmdupl

I built this process based on v.clean manual recommendations.

The bpol tool should be followed by rmdupl. If the -c flag is used with v.clean ... tool=bpol, duplicates are automatically removed.

The rmdupl tool should be used after breaking lines and breaking polygons.

Snapped boundaries may need to be cleaned with break,rmdupl,rmsa. If the -c flag is used with v.clean tool=snap, the sequence of break,rmdupl,rmsa is automatically repeated after snapping until no more small angles a left. Additional cleaning with e.g. tool=rmdanglemay be necessary.

Hint: Breaking lines should be followed by removing duplicates, e.g. v.clean ... tool=break,rmdupl. If the -c flag is used with v.clean > ...tool=break, duplicates are automatically removed.

My data was basically the same, two shapefiles:

• one with points, created manually
• second with polylines, "osm_roades", an OpenStreetMap data.

References:

• Enabling “Snapping” in QGIS while drawing polygons?
• GRASS GIS Wiki | Vector topology cleaning
• Grass Processing tools via QGIS : v.clean snap, chdangle, and rmdangle
• Isochrones: v.iso.net

Note: Executed on QGIS 2.18

In my case, I can suggest several approaches that helped me to overcome an empty output after the execution of v.net.iso.

1. A really trivial and simple one. However, substituting a point layer with an absolutely new shapefile did the work. Even the previous one was correctly snapped. Additionally, the snapping of a new layer to vertexes is necessary. I replaced it after I have "cleaned" my polylines.

2. As was already mentioned by @muri, the implementation of v.clean geoalgorithm makes a tremendous impact.

I made a small graphical model which helped to refine the road network, see the image below. The core logic: bpol > rmdupl > snap > break > rmdupl

I built this process based on v.clean manual recommendations.

The bpol tool should be followed by rmdupl. If the -c flag is used with v.clean ... tool=bpol, duplicates are automatically removed.

The rmdupl tool should be used after breaking lines and breaking polygons.

Snapped boundaries may need to be cleaned with break,rmdupl,rmsa. If the -c flag is used with v.clean tool=snap, the sequence of break,rmdupl,rmsa is automatically repeated after snapping until no more small angles a left. Additional cleaning with e.g. tool=rmdanglemay be necessary.

Hint: Breaking lines should be followed by removing duplicates, e.g. v.clean ... tool=break,rmdupl. If the -c flag is used with v.clean > ...tool=break, duplicates are automatically removed.

My data was basically the same, two shapefiles:

• one with points, created manually
• second with polylines, "osm_roades", an OpenStreetMap data.

References:

• Enabling “Snapping” in QGIS while drawing polygons?
• GRASS GIS Wiki | Vector topology cleaning
• Grass Processing tools via QGIS : v.clean snap, chdangle, and rmdangle
• Isochrones: v.iso.net

Note: Executed on QGIS 2.18

In my case, I can suggest several approaches that helped me to overcome an empty output after the execution of v.net.iso.

1. A really trivial and simple one. However, substituting a point layer with an absolutely new shapefile did the work. Even the previous one was correctly snapped. Additionally, the snapping of a new layer to vertexes is necessary. I replaced it after I have "cleaned" my polylines.

2. As was already mentioned by @muri, the implementation of v.clean geoalgorithm makes a tremendous impact.

I made a small graphical model which helped to refine the road network, see the image below. The core logic: bpol > rmdupl > snap > break > rmdupl

I built this process based on v.clean manual recommendations.

The bpol tool should be followed by rmdupl. If the -c flag is used with v.clean ... tool=bpol, duplicates are automatically removed.

The rmdupl tool should be used after breaking lines and breaking polygons.

Snapped boundaries may need to be cleaned with break,rmdupl,rmsa. If the -c flag is used with v.clean tool=snap, the sequence of break,rmdupl,rmsa is automatically repeated after snapping until no more small angles a left. Additional cleaning with e.g. tool=rmdanglemay be necessary.

Hint: Breaking lines should be followed by removing duplicates, e.g. v.clean ... tool=break,rmdupl. If the -c flag is used with v.clean > ...tool=break, duplicates are automatically removed.

My data was basically the same, two shapefiles:

• one with points, created manually
• second with polylines, "osm_roades", an OpenStreetMap data.

References:

• Enabling “Snapping” in QGIS while drawing polygons?
• Isochrones: v.iso.net

Note: Executed on QGIS 2.18

In my case, I can suggest several approaches that helped me to overcome an empty output after the execution of v.net.iso.

1. A really trivial and simple one. However, substituting a point layer with an absolutely new shapefile did the work. Even the previous one was correctly snapped. Additionally, the snapping of a new layer to vertexes is necessary. I replaced it after I have "cleaned" my polylines.

2. As was already mentioned by @muri, the implementation of v.clean geoalgorithm makes a tremendous impact.

I made a small graphical model which helped to refine the road network, see the image below. The core logic: bpol > rmdupl > snap > break > rmdupl

I built this process based on v.clean manual recommendations.

The bpol tool should be followed by rmdupl. If the -c flag is used with v.clean ... tool=bpol, duplicates are automatically removed.

The rmdupl tool should be used after breaking lines and breaking polygons.

Snapped boundaries may need to be cleaned with break,rmdupl,rmsa. If the -c flag is used with v.clean tool=snap, the sequence of break,rmdupl,rmsa is automatically repeated after snapping until no more small angles a left. Additional cleaning with e.g. tool=rmdanglemay be necessary.

Hint: Breaking lines should be followed by removing duplicates, e.g. v.clean ... tool=break,rmdupl. If the -c flag is used with v.clean > ...tool=break, duplicates are automatically removed.

My data was basically the same, two shapefiles:

• one with points, created manually
• second with polylines, "osm_roades", an OpenStreetMap data.

References:

• Enabling “Snapping” in QGIS while drawing polygons?
• GRASS GIS Wiki | Vector topology cleaning
• Grass Processing tools via QGIS : v.clean snap, chdangle, and rmdangle
• Isochrones: v.iso.net

Note: Executed on QGIS 2.18

In my case, I can suggest several approaches that helped me to overcome an empty output after the execution of v.net.iso.

1. A really trivial and simple one. However, substituting a point layer with an absolutely new shapefile did the work. Additionally, the snapping to vertexes is necessary. I replaced it after I have "cleaned" my polylines.

2. As was already mentioned by @muri, the implementation of v.clean geoalgorithm makes a tremendous impact.

I made a small graphical model which helped to refine the road network, see the image below. The core logic: bpol > rmdupl > snap > break > rmdupl

I built this process based on v.clean manual recommendations.

The bpol tool should be followed by rmdupl. If the -c flag is used with v.clean ... tool=bpol, duplicates are automatically removed.

The rmdupl tool should be used after breaking lines and breaking polygons.

Snapped boundaries may need to be cleaned with break,rmdupl,rmsa. If the -c flag is used with v.clean tool=snap, the sequence of break,rmdupl,rmsa is automatically repeated after snapping until no more small angles a left. Additional cleaning with e.g. tool=rmdanglemay be necessary.

Hint: Breaking lines should be followed by removing duplicates, e.g. v.clean ... tool=break,rmdupl. If the -c flag is used with v.clean > ...tool=break, duplicates are automatically removed.

My data was basically the same, two shapefiles:

• one with points, created manually
• second with polylines, "osm_roades", an OpenStreetMap data.

References:

• Enabling “Snapping” in QGIS while drawing polygons?
• Isochrones: v.iso.net

Note: Executed on QGIS 2.18

In my case, I can suggest several approaches that helped me to overcome an empty output after the execution of v.net.iso.

1. A really trivial and simple one. However, substituting a point layer with an absolutely new shapefile did the work. Even the previous one was correctly snapped. Additionally, the snapping of a new layer to vertexes is necessary. I replaced it after I have "cleaned" my polylines.

2. As was already mentioned by @muri, the implementation of v.clean geoalgorithm makes a tremendous impact.

I made a small graphical model which helped to refine the road network, see the image below. The core logic: bpol > rmdupl > snap > break > rmdupl

I built this process based on v.clean manual recommendations.

The bpol tool should be followed by rmdupl. If the -c flag is used with v.clean ... tool=bpol, duplicates are automatically removed.

The rmdupl tool should be used after breaking lines and breaking polygons.

Snapped boundaries may need to be cleaned with break,rmdupl,rmsa. If the -c flag is used with v.clean tool=snap, the sequence of break,rmdupl,rmsa is automatically repeated after snapping until no more small angles a left. Additional cleaning with e.g. tool=rmdanglemay be necessary.

Hint: Breaking lines should be followed by removing duplicates, e.g. v.clean ... tool=break,rmdupl. If the -c flag is used with v.clean > ...tool=break, duplicates are automatically removed.

My data was basically the same, two shapefiles:

• one with points, created manually
• second with polylines, "osm_roades", an OpenStreetMap data.

References:

• Enabling “Snapping” in QGIS while drawing polygons?
• Isochrones: v.iso.net