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I am having a fairly specific issue. I am starting off by creating 100m2 squares around specific points on a map by adding a buffer to the point and then using this buffer as the extent for a Vector grid. This works fine in that it creates the squares as needed but when I export the shp files to create gpx files for use in the field with a garmin etrex 20 I find that instead of the file representing one track as a square, it is instead 4 tracks each representing one side of the square.

I have traced the problem back to when the squares are created by Vector Grid. The attribute table shows 4 different lines being created rather than one polyline. How do I merge these 4 lines into 1 so that I can then continue with the rest of the workflow to create the squares as needed.

I realise I could manually edit the final gpx file in Notepad but this seems a long winded way of solving the problem. I have also tried outputting as polygons rather than lines in Vector Grid but for some reason is then gives me 200m2 squares instead of 100m.

The squares are needed for field research in precise locations and it is critical that the centre point is followed and the researcher can easily follow the Garmin to find the relevant grid when in the landscape.

  • I think this might be a duplicate of gis.stackexchange.com/questions/67057/… as the answer there of using Vector>Geoprocessing Tools>Dissolve appears to work following a quick, one square test. Will update if it works well with all squares when merged as one gpx file tomorrow. – Tatone Oct 8 '15 at 21:08
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Double checked this morning and the above method worked. The final method was as follows:

  1. Use Vector>Geoprocessing Tools>Dissolve on each shp file so that they have only one entry row in the attribute table
  2. Edit the table for each of the new shapefiles (it helps to have the new files in a group so that you don't get confused) in turn to add an additional column called 'name' with the desired track name entered as a string.
  3. Merge the shapefiles using Vector>Data Management Tolls>Merge Shapefiles to One...
  4. The outputted merged shapefile can then be saved as a gpx file in the WGS 84 CRS, leaving skip attribute creation unchecked and selecting YES for FORCE_GPX_TRACK (if you skip attribute creation the names will not be exported).

The resulting file displays on the Garmin as a series of tracks all with the names as displayed in the name column of the attribute table. I hope this helps someone else in the future.

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