How the Calculator Works
This calculator applies the World Meteorological Organization's siting criteria for surface weather observations, adapted for consumer weather station installations. It evaluates three key constraints:
- Structure proximity: The 4:1 rule — your temperature sensor needs to be at least 4 times the height of any nearby structure or obstruction away from it. A 20-foot house requires 80 feet of clearance for a perfect installation, though practical compromises are scored and explained.
- Pavement heat bias: Hard surfaces re-radiate absorbed solar heat and elevate nearby air temperatures. The calculator quantifies the expected temperature error from your described pavement proximity and recommends mitigation strategies.
- Surface type impact: Grass and soil surfaces stay cooler through evapotranspiration. Gravel and concrete amplify daytime heating. Your surface type is factored into both the temperature sensor height recommendation and the expected accuracy rating.
Rain gauge and anemometer recommendations follow separate rules — rain gauges need to avoid both wind shadow effects (which reduce measured rainfall) and splashback from hard surfaces, while anemometers need clear exposure above the height of surrounding obstructions.
Understanding Your Placement Score
Scores are rated on a 1–100 scale per sensor:
- 80–100 (Excellent): Meets WMO Class 1 or 2 siting criteria. Data quality acceptable for citizen science reporting and CWOP contribution without caveats.
- 60–79 (Good): Meets WMO Class 3 criteria. Minor biases possible but data is useful and representative for most purposes. Acceptable for CWOP with noted placement constraints.
- 40–59 (Fair): WMO Class 4. Measurable siting biases expected. Data useful for relative comparisons and trend analysis but not directly comparable to Class 1–3 stations.
- Below 40 (Poor): Significant expected siting errors. Consider relocation or note limitations prominently in station descriptions.
Want the full placement rules? Read our detailed radiation shield placement guide, rain gauge placement guide, and anemometer height guide for the complete reasoning behind each recommendation.