-2

I need to draw a polygon shape around Tobermory and Bunnehaven, (these are situated at the top of Figure 1 below. The issue I have with this image is that I am finding it hard to geo reference. As you can see I only have Northings and Westings? and I have no idea how to convert them or plot longitude or latitude within the Raster --> georeferencer tool. So, does anyone know how to provide longitude and latitudes for this figure?

If this is not possible is there a way to just copy the image onto QGIS and essentially draw around the shapes by creating a new shapefile and selecting polygon data. then with my drawn polygon, place it on my basemap?

enter image description here

  • 4
    your Northings and Westings are the lat long so you have 5 labeled intersections to use as georeferencing points and you can use the smaller unlabeled ones too with some simple maths, – Ian Turton Nov 30 '18 at 10:48
  • The georeference tool asks you for coordinates, you may simply enter them manually instead of clicking a point on your mapscreen. – Erik Nov 30 '18 at 10:54
  • So would my 'X/East' be my Westing and would 'Y/North' be my Northings?, if I was to enter my data within the georeferencer manually? – Bodhi Nov 30 '18 at 10:59
  • 1
    You have the necessary data on the map for binding and for further digitization... – Cyril Nov 30 '18 at 13:37
3

Actually you have the map in UTM, zone 30. You can use georeferencing plugin for referencing such maps. The only problem is that you should recalculate coordinates from longitude latitude to plane coordinates of UTM/30. Georeferencing using 4 points This is a georeferenced map on Open Street Map

To simplify picking coordinates you can use plugin 'Create grid'. This plugin helps creating points in the nodes of a grid with predefined steps along X and Y axises (one degree in your case). The map image tied to grid nodes

If georeferencing operations have to be done frequently you need a special plugin. In fact, once I made the tool that placed a selected image on the view of a map. There were only two parameters which should have been specified: a resolution and scale of the source map image.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.