Forgot the last step: 5) To get a line layer, run the "Polygons to lines" algorithm on the output layer from step four.
Håvard On 17.07.2020 10:00, Håvard Tveite wrote: > Hi Paul, > > I don't think you will find a function in QGIS to do this, > but you should be able to achieve it by using the following > procedure: > > 1) Create a polygon grid with the same "spacing" as your point grid. > Use the "Create grid" algorithm (from the Processing Toolbox), with > Grid type: Rectangle (Polygon) > Grid extent: Click on the ... pull-down and select "Calculate from > layer", and select your point layer > Horizontal spacing: 25 meters > Vertical spacing: 100 meters > > 2) Run the "Join attributes by location (summary)" algorithm with > Input layer: the generated polygon grid from the first step > Join layer: your point grid > Geometric predicate: "intersects" > > 3) Run the algorithm "Select by Attribute" with > Input layer: your "Joined layer" (from step two) > Selection attribute: one of the *_count attributes > Operator: = > Value: 4 > Modify current selection by: creating new selection > > 4) Run the "Dissolve" algorithm with > Input layer: your "Joined layer" from step 2-3 > check "Selected features only" > > This should work (but rounding errors may cause problems in > step two and four) > > Håvard > > On 17.07.2020 07:21, Paul T A Drea wrote: >> Hello list, >> >> I hope this finds everyone safe and healthy during these trying times. >> >> I am using a MacBook Pro running macOS 10.15 (Catalina). >> >> QGIS version 3.14.0-Pi. QGIS code revision 9f7028fd23. >> >> I have a shp file containg 2 653 337 points in an orthononal grid with >> 25m x 100m spacing of the points. >> >> The grid is oriented north south. These points are in lines spaced 25m >> in the easting (X) direction and 100m northing (Y) direction. >> >> I would like to apply a polygon as a boundary (red) as shown in the >> screen grab below. >> >> >> I have not been able to achieve this using convex hull as the final >> output does not take into acount the sawtooth steps. >> >> Any help or pointers would be appreciated thanks. >> I am not a coder and have no knowledge of writing any scripts. >> >> Thanks and Best regards, >> Paul >> >> >> -- >> >> */Paul T. A. Drea/* >> >> *Geodetic Consultant* >> >> *Cell Greece: +30-698 052 0611* >> >> *Cell Abu Dhabi: +971 50 595 6547* >> >> *Cell U.K.: +44 7507 975162* >> >> *SKYPE: paul.drea* >> >> *e**-mail 1: **[email protected]* <mailto:[email protected]> >> >> *e**-mail 2: **[email protected]* <mailto:[email protected]> >> > _______________________________________________ Qgis-user mailing list [email protected] List info: https://lists.osgeo.org/mailman/listinfo/qgis-user Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
