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Digitizer

The digitizer is the precision drawing tool for capturing facility geometry directly on the map. It supports snapping to existing features, geometric constraints (perpendicular, parallel, fixed length), and — planned — GPS-trace import. Use it when shape-tool drawing is not precise enough, or when the geometry has to follow specific dimensional rules.

Learning objectives

By the end of this lesson you should be able to:

  • Use the digitizer to capture facility geometry with snapping enabled
  • Apply geometric constraints during a draw
  • Recognize when imagery accuracy limits the digitizer's effective precision

When to use the digitizer​

Reach for the digitizer when:

  • The facility's footprint must be drawn at exact dimensions (e.g., a 60 ft × 30 ft magazine)
  • The new geometry needs to align with existing features (snap-to-edge or snap-to-vertex)
  • You're capturing geometry from a survey or drawing where precision matters

For quick sketching or approximate placement, the simpler shape tools in Adding features are usually sufficient.

[TODO: FILL IN — exact entry point for the digitizer in the current Siter UI.]

Snapping​

Snapping latches the cursor to nearby reference points as you draw:

  • Vertex snap — corners of existing features
  • Edge snap — anywhere along an existing feature's edge
  • Grid snap — regular grid points (where supported)

Snapping is on by default during digitizer use. Toggle it off when you need to place a vertex truly free of any nearby reference.

[TODO: FILL IN — snap toggle controls, snap-tolerance setting, and any visual indicator showing what is being snapped to.]

Constraints​

Geometric constraints lock specific properties of the geometry as you draw:

  • Perpendicular — the next segment is forced 90° to the previous
  • Parallel — the next segment is forced parallel to a chosen reference segment
  • Fixed length — the segment length is locked to a specified value
  • Fixed angle — the segment direction is locked to a specified angle

Constraints stack — you can require both perpendicular and fixed length on the same segment.

[TODO: FILL IN — exact UI for activating each constraint mid-draw and providing the constraint values.]

GPS traces​

GPS-trace import is planned but not yet available in the digitizer. Once shipped, the workflow will be: import a GPS trace → snap-trace into a feature footprint → confirm.

[TODO: FILL IN — once implemented, document the import flow here.]

Imagery precision is the cap​

The digitizer is as precise as the imagery you draw against. If the base map is satellite imagery with 1 m resolution, digitizing a 60 ft × 30 ft magazine to sub-foot precision is a false precision — the placement is only as accurate as the imagery beneath it. For high-precision work, use georeferenced imagery (see Background imagery and QGIS) or import the geometry directly via shapefile or GeoJSON.

Try it​

In the digitizer:

  1. Start a new polygon feature with snapping on, drawing against an existing feature's edge
  2. Apply a perpendicular constraint and place the next vertex
  3. Apply a fixed-length constraint of 30 ft and place a third vertex
  4. Close the polygon and confirm the dimensions match the constraints
  • Adding features — quicker shape tools for non-precision work
  • Background imagery — imagery precision caps the digitizer
  • Shapefile import — alternative path for high-precision external geometry
  • QGIS — for georeferencing scanned drawings before digitizing against them
  • Capability reference: Tools