Circular buffers

by user2105469   Last Updated January 14, 2018 01:22 AM

I have a coastal line layer ( us-medium-shoreline from http://shoreline.noaa.gov/data/datasheets/medres.html ), which is loaded into a project with On-The-Fly reprojection ( WGS 84 / World Mercator CRS with +proj=merc +lon_0=0 +k=1 +x_0=0 +y_0=0 +datum=WGS84 +units=m +no_defs) and I'd like to create a 500m buffer around this shoreline with the ultimate goal of intersecting the shoreline with inland polygons.

I'm expecting a polygon with the coastal line as its center, but I keep getting a circular region as resulting layer (with empty attributes table). Clearly I'm missing something as a GIS newbie.

Tags : qgis


Answers 2


I'm guessing it is b/c your layer is in geographic coordinate system (Nad83) not projected coordinate system. Perform a save as on the layer and change the CRS to a projected coordinate system then try the buffer on the new projected layer.

artwork21
artwork21
March 30, 2015 14:43 PM

You have not mentioned what buffer size you entered.

If the source data is in degrees, the buffer size will be in degrees too, while a source in meters results in a buffer size in meters.

To avoid confusion, turn OTF off and see if both layers still align.

AndreJ
AndreJ
March 30, 2015 16:47 PM

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