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Like many people in geology and archaeology I need to work with local grids that have eastings and northings from a specific reference point, and typically have a difference alignment/direction of north to true north.

1) Any way to create such grids in QGIS?

2) If I need to rotate layers that contain groups of points, lines or polygons in QGIS is the affine translation plug in the only way? If so can someone point me to an online calculator that can covert simple rotation angle, scale factor and rotation orgin values into the transformation matrix values required by the plug in ([x'=, x+, y+][y'=, x+, y+])?

3) Questions about local grids and rotation in QGIS are very common. How much time would it take a programmer to put together a plugin to create local grids and/or do vector rotations on groups of points, lines or polygons?

If answering – please note I am not a mathematician or programmer, and I have no idea what Python is.

  • As a non-archaeologist, my first question is: Do you define the grid on site, or do you do so beforehand and hope you covered everything? – Erik Aug 1 '18 at 6:39
  • Maybe related: gis.stackexchange.com/questions/83861/… (which works on QGIS too). – AndreJ Aug 1 '18 at 12:03
  • That's a bit over the top I think, since OP seems to want to procude a grid of up to 1 km x 1 km for local excavations/research. – Erik Aug 1 '18 at 12:50
  • Thanks for that - the grids are defined beforehand - with grid north usually oriented with the orientation of the site. Most local grids are <1 km wide, and almost all are <10km wide. All I need (as well as many others) is a simple way to set a grid origin and orientation. – Rohan Aug 2 '18 at 6:28

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