SME
Surveying · Problem type
Position error from DOP
Use this for “PDOP is 2.1 and each range has a 3 m error. What position error should you expect?”
Chart
This is an example. Type your own values to start a new problem.
σP (m)
=
PDOP
×
σ (m)
Formulas
σP
=
PDOP
×
σ
6.3 = 2.1 × 3
Assumptions
•
DOP (dilution of precision) measures the satellites’ geometry: spread across the sky gives low DOP, bunched gives high.
•
PDOP is the position (3D) DOP; it scales the range error into the position error.
•
Every range has the same random error σ, independent of the others.
Step-by-step
WE KNOW
PDOP = 2.1, σ = 3 m
FIND
position error (σP)
Step 1 · Find position error (σP)
Use σP = PDOP × σ
The geometry multiplies each range’s error into the position’s error.
σP = 2.1 × 3
σP = 6.3 m
Check
Put the numbers back in. Both sides should match.
6.3 = 2.1 × 3 ✓
Topic check
See what you know: 5 questions on this topic
New questions each time. Pass to mark it complete.