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I have created a boat traffic map on QGIS 3.36.2. Here, I have a vector layer containing different points connected to show the boat routes in the Andaman and Nicobar Islands in India. To ensure that my CRS is consistent and in metres, I have double-ensured all my layers were set to EPSG:32646 - WGS 84 / UTM zone 46N, when creating them.

Layer with all the way points

CRS of this 'Merged' way point layer set to UTM 46N

Created Routes by connecting the way points using 'Points to Path' tool

Output of Points to Path, showing all routes

However, now when I wanted to add a buffer of 200m along the boat routes, the buffer instead surrounds all of India, and not just the routes. I realised then that when measuring two points on my map that are supposed to be at a distance of 100m, the measuring tool is showing them to be 0.001 m afar.

Creating a buffer, using the Paths as input, and distance in meters

Buffer layer exceeding specified distance...

...Covering entirety of map

The points here are supposed to be 150 m apart... but are much smaller when measured

So, the buffer is technically still picking up what is correctly 200m, but the map itself is super-shrunken and I cannot figure out how to fix this. I'm relatively new to GIS.

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  • 3
    Your layer still seems to be in a geographic CRS, not in UTM. Can you share a sample of your data a in d tell step by step how you create the layer and how you "set the CRS"?
    – Babel
    Commented Jun 24 at 6:50
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    Make sure it doesnt say degrees in the buffer dialogue
    – Bera
    Commented Jun 24 at 7:10
  • When creating a layer by importing dataset from a csv file, for instance, was when I selected my desired CRS itself rather than reprojecting or exporting and then saving it as wanted (though this is also something I tried but achieved the same results). Further ahead I merged the layers with the different waypoints, and then used the "points to path" tool to create my routes, again selecting 46N CRS here itself. However, from here on, when generating the buffer layer, the distance metric- even while being in "metres" (and not degrees), gives me the same output
    – Amisha Nakhwa
    Commented Jun 24 at 8:44
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    Share a sample of your data. Otherwise it's difficult to help. And as long as you don't show us step by step what settings you made, it's impossible to say where somthing went wrong. Please edit you initial question and add these details, e.g. screenshots.
    – Babel
    Commented Jun 24 at 8:55
  • I have added screenshots of the steps. My data consisted of the coordinates I have added as points highlighted in image 1.
    – Amisha Nakhwa
    Commented Jun 26 at 9:37

1 Answer 1

Reset to default
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Looking at the x and y value displayed in the mesure tool it seem that your data are still on a geographic system so your reprojection step didn't work or you made an error at some point.

To fix that :

  • first use the Assign projection tool to set back all your data to the original geographic CRS (probably WGS84 epsg:4326 but check to made sure) this tool just change the CRS information of layers, it didn't change actual coordinate or geometry.
  • Then use the Reproject layer tool to project your layer to your desired projected CRS (WGS 84 / UTM zone 46N epsg:32646). This tool create a new layer with updated coordinate, geometry and CRS information

After these two step you should be able to create your buffer at the right size

A good practice is to add a basemap to your project (you may use the QuickMapServices plugin for that) so you may check at each step that there are no error by checking that the data appear in the right place at the right scale

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  • As long as it is not clear what OP actually did, it is a risky advice to use Assign projection - uninformed (miss-)use of this tool is probably the most common error and most often asked questions here. As a general rule, I would advice to never use this if people are not 100% sure what they do (and in this case, they won't end up here with this problem). I would rather advice to create a new QGIS project and load the layers again from scratch, than they should load correctly. Regardless, still your answer is worth of +1 :-)
    – Babel
    Commented Jun 26 at 10:43
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    @Babel your are right about the use of Assign projection. My answer is based on the assumption that the error was to select the wrong CRS when loading CSV data : "When creating a layer by importing dataset from a csv file, for instance, was when I selected my desired CRS itself rather than reprojecting or exporting" and that any later reprojection to UTM zone 46N did nothing as the CRS was already set as UTM zone 46N...
    – J.R
    Commented Jun 26 at 11:42
  • @J.R I made sure to stick to UTM 46N from then since I did not need to reproject as it was anyway in my desired CRS.
    – Amisha Nakhwa
    Commented Jun 28 at 4:33
  • Perhaps I should restart the project from scratch as @Babel suggested and hope it goes right then :)
    – Amisha Nakhwa
    Commented Jun 28 at 4:34
  • @AmishaNakhwa if your csv coordinates are not UTM 46N then you have to reproject at last once ( when loading csv you need to set the actual CRS, not the desired one)
    – J.R
    Commented Jun 28 at 6:55

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