Visualizing Common GIS Digitizing Errors

 To help visualize common GIS digitizing errors, I have created a comprehensive SVG graphic using Inkscape software. Each error is isolated and labeled to demonstrate the specific topological or geometric issue it represents.

The SVG file is here below, copy the SVG code into a text editor and save it with .svg extension.

<svg viewBox="0 0 800 600" xmlns="http://www.w3.org/2000/svg">
  <rect width="800" height="600" fill="#f8f9fa" />
  
  <style>
    .label { font-family: sans-serif; font-size: 12px; font-weight: bold; fill: #333; }
    .error-mark { fill: #e74c3c; stroke: #c0392b; stroke-width: 2; fill-opacity: 0.6; }
    .base-geo { fill: #3498db; stroke: #2980b9; stroke-width: 2; fill-opacity: 0.4; }
    .point { fill: #2c3e50; }
    .highlight { stroke: #e67e22; stroke-width: 3; stroke-dasharray: 4; }
  </style>

  <g transform="translate(50, 50)">
    <path d="M 0,0 L 100,0 L 0,80 L 100,80 Z" class="error-mark" />
    <text x="0" y="110" class="label">Self Intersection</text>
  </g>

  <g transform="translate(200, 50)">
    <path d="M 0,80 L 50,20 L 100,80" fill="none" stroke="#2980b9" stroke-width="2" />
    <circle cx="50" cy="20" r="4" class="point" />
    <circle cx="52" cy="22" r="4" fill="red" opacity="0.7" />
    <text x="0" y="110" class="label">Duplicate Nodes</text>
  </g>

  <g transform="translate(350, 50)">
    <path d="M 0,0 H 100 V 80 H 0 Z M 30,30 V 50 H 70 V 30 Z" class="base-geo" fill-rule="evenodd" />
    <text x="0" y="110" class="label">Hole (Undesired)</text>
  </g>

  <g transform="translate(500, 50)">
    <path d="M 0,80 L 45,80 L 48,78 L 100,80" fill="none" stroke="#2980b9" stroke-width="2" />
    <circle cx="46.5" cy="79" r="8" fill="none" stroke="red" />
    <text x="0" y="110" class="label">Short Segment</text>
  </g>

  <g transform="translate(650, 50)">
    <path d="M 0,80 L 100,75 L 0,70" fill="none" stroke="red" stroke-width="2" />
    <text x="0" y="110" class="label">Minimum Angle</text>
  </g>

  <g transform="translate(50, 200)">
    <rect x="40" y="40" width="10" height="10" class="error-mark" />
    <text x="0" y="110" class="label">Minimum Area</text>
  </g>

  <g transform="translate(200, 200)">
    <path d="M 0,40 Q 50,35 100,40 Q 50,42 0,40" class="error-mark" />
    <text x="0" y="110" class="label">Sliver Polygon</text>
  </g>

  <g transform="translate(350, 200)">
    <rect x="10" y="10" width="80" height="60" class="base-geo" />
    <rect x="15" y="15" width="80" height="60" class="error-mark" opacity="0.4" />
    <text x="0" y="110" class="label">Duplicate Features</text>
  </g>

  <g transform="translate(500, 200)">
    <rect x="0" y="0" width="100" height="80" class="base-geo" />
    <circle cx="50" cy="40" r="20" class="error-mark" />
    <text x="0" y="110" class="label">Feature in Feature</text>
  </g>

  <g transform="translate(200, 350)">
    <rect x="0" y="0" width="80" height="80" class="base-geo" />
    <rect x="60" y="20" width="80" height="80" fill="#e74c3c" fill-opacity="0.5" stroke="#c0392b" />
    <text x="30" y="120" class="label">Overlap</text>
  </g>

  <g transform="translate(450, 350)">
    <path d="M 0,0 L 70,0 L 65,80 L 0,80 Z" class="base-geo" />
    <path d="M 80,0 L 150,0 L 150,80 L 85,80 Z" class="base-geo" />
    <text x="45" y="120" class="label">Gap (Sliver)</text>
  </g>
</svg>

Self Intersection:- A polygon boundary crosses over itself. Breaks validity in OGC standards; creates "figure-eight" shapes.

Sliver Polygons:- Long, thin polygons often created by overlapping boundaries. Inflates feature count and messes up area calculations. This error come from very small polygon (with small area) with a large perimeter

Gaps & Overlaps:- Polygons that should be adjacent have space between them or sit on top of each other. Leads to "double counting" or "missing data" in spatial joins.

Minimum Angle:- Vertices are too close, creating a sharp "spike." Causes rendering artifacts and issues with offset/buffer tools.

Duplicate Nodes:- Multiple vertices at the same coordinates. Increases file size and slows down processing without adding detail.

Thank you for reading.