Acara 8 Geoprocessing Peta QGIS

Summary

The video demonstrates basic vector geoprocessing in QGIS using administrative boundaries, roads, rivers, and agricultural-garden polygons for Wonosobo Regency, focusing on Wadaslintang subdistrict. The presenter loads the shapefile layers, saves processed outputs as separate files, and explains how to prepare the results for mapping.

Workflow and tools

Prepare the project

• Create a project folder and add the village-administration, road, river, and agricultural-garden layers.
• Inspect the administrative layer’s attribute table to identify the field used to group villages by subdistrict.

Dissolve

Dissolve combines adjacent polygons that share a chosen attribute into larger features. The demonstration dissolves village boundaries using the subdistrict-code field, identified in the subtitles as WADMKC, to create subdistrict areas.

Select and export a subdistrict

Identify Wadaslintang in the administrative data and export its boundary as a separate layer. This boundary is then used to restrict other layers to the subdistrict.

Clip

Clip cuts input features to the boundary of a selected area. The presenter clips roads and rivers to Wadaslintang, then clips the agricultural-garden layer.

Before clipping the agricultural-garden polygons, the presenter checks for invalid geometry and runs Fix Geometries when needed. The tutorial also emphasizes saving each result as a new file rather than overwriting or confusing it with the source layer.

Merge

Merge combines layers into a single output layer. The example merges the clipped roads and rivers. The presenter checks the output attribute table to confirm that it includes features from both inputs.

Intersect

Intersect keeps the area shared by two input layers. The example intersects the agricultural-garden layer with the Wadaslintang boundary to show where the garden polygons fall within the subdistrict.

Union

Union combines the coverage of two polygon layers and retains information from both, including their overlapping areas. The tutorial contrasts this with Intersect: Intersect keeps only the shared area, while Union includes areas from both inputs.

Buffer

Buffer creates a zone around features at a specified distance. The presenter buffers the river layer using a projected coordinate system with meter units.

Clarification: The tutorial describes a buffer distance of 20 m as producing 10 m on each side. In standard QGIS buffering, a 20 m distance normally extends 20 m from the feature on each side. Confirm the intended distance before using the result.

Presentation and map styling

The presenter changes layer colors and demonstrates categorized symbology to distinguish roads and rivers. The final map is intended to focus on the clipped subdistrict layers and related outputs.

Speakers and sources featured

• Speaker: One unnamed presenter or instructor; no other speakers are identifiable in the subtitles.
• GIS layers discussed: Village-administration boundaries, roads, rivers, and agricultural-garden polygons for the Wonosobo/Wadaslintang area. The subtitles do not identify the original data providers.