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.

List of USGS EROS data portals

 The USGS Earth Resources Observation and Science (EROS) Center provides access to extensive satellite, aerial, and land surface data through several key portals. The primary platforms for searching and downloading imagery are EarthExplorer and GloVis. 

As of the year 2026, the USGS Earth Resources Observation and Science (EROS) Center continues to provide specialized portals for accessing satellite imagery and geospatial datasets. Accessing most of these services requires an account via the EROS Registration System (ERS).

Portal website links are provided below;-

1) EarthExplorer (EE) - https://earthexplorer.usgs.gov/
2) Global Visualization Viewer (GloVis) - https://glovis.usgs.gov/
3) LP DAAC (Land Data) - https://lpdaac.usgs.gov/
4) EROS Science Processing (ESPA) - https://espa.cr.usgs.gov/
5) Commercial Cloud Data (AWS) - https://registry.opendata.aws/
6) Machine-to-Machine (M2M) API - https://m2m.cr.usgs.gov/
7) Bulk Download Application (BDWA) - https://ebulk.cr.usgs.gov/
8) HDDS Explorer (Hazards/Disasters) - https://hdds.usgs.gov/
9) EarthNow! Landsat Viewer - https://earthnow.usgs.gov/
10) LANDFIRE Map Viewer - https://www.landfire.gov/viewer/
11) Multi-Resolution Land Characteristics (NLCD) - https://www.mrlc.gov/viewer/
12) Coastal Elevation Database (CoNED) - https://www.topotools.cr.usgs.gov
13) Monitoring Trends in Burn Severity (MTBS) - https://www.mtbs.gov/
14) AppEEARS (Data Subsetting) - https://appeears.earthdatacloud.nasa.gov/
15) IntELiMon Viewer (Interagency Ecosystem LiDAR Monitoring) - https://dmsdata.cr.usgs.gov/lidar-monitoring/viewer/
16) LRESA (Landsat Reprocessing Events Search Application) - https://lresa.cr.usgs.gov/
17) Spectral Characteristics Viewer - https://landsat.usgs.gov/spectral-characteristics-viewer
18) Fire Danger Viewer - https://fire-danger-viewer.cr.usgs.gov/
19) EROS Registration System (ERS) - https://ers.cr.usgs.gov/

That is it!