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I'm new to QGIS and stuck. I have a shapefile of 1 ft contours for an area. I want to load it into mapbox so I can turn it into a layer for Gaia GPS, but the shapefile is too big for mapbox and it gives an error. I was told I could use QGIS to cut out a smaller piece from the contour map but I can't figure out how to do that. I can load the contour map and see all the contours, but can't figure out how to select a portion of it and save to a new shapefile.

Vince
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Toby Stensland
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  • That was the hint I needed and led me to a few other sources that helped. Here are my QGIS newbie instructions to clip, crop or create a subset of a shapefile.

    Run QGIS Desktop.

    I then found Vector->GeoprocessingTools->Clip, but first I needed to create a new layer

     – Toby Stensland Feb 16 '19 at 02:11

  • Run QGIS Desktop.

  • Find the source shp file in the Browser pane and double-click. It will open as the 1st layer in new project.

  • Layer->CreateNewLayer->NewShapefileLayer. File name needs to include full path. GeometryType=Polygon. CRS set to same as source shapefile which is EPSG:6428 in my case. Click "OK".

  • In Layers pane, right-click on new layer and click "Toggle Editing".

    • – Toby Stensland Feb 16 '19 at 02:44

  • With new layer selected do Edit->AddPolygonFeature. Left-click on map to create corners of your rectangle. Right-click when done. Click "OK" in the little window that pops up and you should see your rectangle.

  • Go to Vector->GeoprocessingTools->Clip. Pick your source shapefile as InputLayer. Pick the new rectangle layer as OverlayLayer. Click "Run" and close the Clip window when it is done.

  • In Layers pane, select the new Clipped layer and then do Layer->SaveAs. Format=ESRI Shapefile. Choose a file name and it needs full path. Click "OK".

    • – Toby Stensland Feb 16 '19 at 02:44
  • The topic "Clipping line layer based on polygons with QGIS" tells me to use the Clip tool, but I still had to figure out how to make the Overlay Layer. – Toby Stensland Feb 16 '19 at 02:49
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    From your third point starts you own answer. Keep in mind: a Geographic Information System it is not a tool that you can use for the first time and use without problems. In addition to managing geographic projections, vector and raster files, data and metadata; you must understand how its interface works. For basic operations in QGIS, the best thing you can do is to review the sections of the User Guide and the Training Manual to find what you need. – Gabriel De Luca Feb 16 '19 at 04:42