QGIS Line Clip Issue

Question

I'm trying to use QGIS 3.4.14 to clip a subsection of a larger map. What I tried doing was creating a new polygon shapefile layer, then using "Add Polygon Feature" to enclose the Falkland Islands/Islas Malvinas. I then went to Vector -> Geoprocessing Tools -> Clip and selected the layer with the polygon enclosure as the overlay layer and the layer named "Límites"(a line layer) as the input layer. It works...sort of. The layer containing the clip includes the outline of the coast of the Falklands/Malvinas, but I also get several other groups of lines farther out from the coastline. I don't want these. "Límites" is organized as some sort of hierarchy or grouping. What I want is just "Línea de costa", but the clip operation is also picking up "Límite del Mar Territorial Argentino" and "Línea de base".

I have tried hiding the unwanted elements and even deleting them prior to the clip, but they always show up. How do I get QGIS to only clip the "Línea de costa" object? This is what I get after the clip:

The file is publicly available here:

Direct file link:

https://www.ign.gob.ar/archivos/sig250/Mapa_Argentina_Bicontinental_QGIS.rar

Page link:

https://www.ign.gob.ar/NuestrasActividades/InformacionGeoespacial/CapasSIG

Answer 1

The structure depicted in your layer tree panel is a categorized style applied to the line layer. You can't think of those categories as separate layers, they all represent features belonging to the 'limites' layer. But each category has a different symbology applied based on the attribute in the 'Objeto' field. So when you select 'limites' as the input layer for the clip operation, of course all features will be included in the output.

If I understand correctly that you just want to extract the coastline of the Falkland Islands (Islas Malvinas), I would take the following approach.

1. Right click on 'limites' in the layer panel and select Filter.

2. Use the query: "Objeto" LIKE '%costa' to filter the layer to only show 'coast line' features.

3. Zoom to your area of interest.

4. Activate the 'Select features' tool then click and drag the rubber band to select the features you want to extract (see below).

5. Now you should see that just the coast lines of Falkland Islands are selected (highlighted in yellow). Now right click again on the 'limites' layer and select 'Export' then 'Save Selected Features As'. Choose a format (gpkg) is the default, and file location and click OK.

You should now have a new layer containing only the coast lines in which you are interested, similar to the result below.