Satellite geometry and DOP
Each satellite gives one range. How the satellites are spread across the sky decides how those range errors turn into position error. Drag satellites on the sky plot and watch the dilution of precision (DOP) and the horizontal error ellipse change.
Starting...
Sky
Satellites for a new sky
Errors
Range error σUERE
Elevation mask
Drag a satellite on the sky plot. Satellites below the mask (gray) are not used.
Sky plot: zenith in the middle, horizon at the edge, north up.
1σ horizontal error ellipse, with 300 simulated fixes.
Try this
- Press Spread out, then Bunched. Same number of satellites, same range error, but the position error grows several times.
- Press All high. Every DOP gets worse, and VDOP explodes: with no low satellites, height and the receiver clock are hard to tell apart.
- Press Street canyon. Only satellites along a north-south street are visible, so the ellipse stretches east-west.
- Raise the elevation mask until a satellite turns gray. Dropping one low satellite can change DOP more than adding a high one.
Notebook
Work with the same script in cells, like Jupyter, right here in the browser. Edit any cell and run it. Nothing is saved: Reset brings a cell back, and Download .ipynb keeps your edited version for VS Code or Jupyter.
Loading Python...
The Python script: sat_dop.py
This is the script the page runs. Run it yourself with python3 sat_dop.py.