Data & ModelM-NCPPC · Montgomery Parks
Avg Model MAPE
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Mean Absolute % Error
Avg R²
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Coefficient of determination
Data Layers
6 sources
Census, LODES, OSM, DOT, GTFS, GIS
Calibration Results — 2024 vs. Reference Counts
Predicted estimates vs. available reference data. Adjustment factors applied per AOI.
| Area | Predicted | Reference | MAPE | R² | Adj. Factor | Status |
|---|
Methodology — Bias & Limitations Disclosure
Per RFP P46-120 Section V requirements. All known biases and limitations disclosed below.
Sampling Bias
Population proxies from Census ACS may under-represent low-income and limited-smartphone populations. Calibration partially corrects for this.
Geographic / Spatial Bias
Sub-0.1-mile AOI boundaries may introduce edge effects. Areas near sensitive locations (schools) apply 50m exclusion buffers.
Temporal Limitations
Seasonal curve derived from DOT statewide data, not park-specific. Individual park patterns may deviate ±15% from model.
Transit Corridors
Purple Line estimates use GTFS boarding data + gravity model. Individual trip tracking not available; accuracy ±20–30% for micro-segments.
Data Recency
Census ACS data lags 1–3 years. Rapid demographic shifts in developing areas may reduce accuracy until next calibration cycle.
Algorithmic Limitations
Gravity model assumes isotropic decay. Physical barriers (highways, rivers) are partially accounted for via OSM routing.
Data Sources & Attribution
| Source | Type | Used For | Update Freq. | Cost |
|---|---|---|---|---|
| US Census ACS 5-Year | Demographic | Population, income, commuting | Annual | Free |
| LEHD LODES | Employment/Resident | Origin-destination baseline | Annual | Free |
| OpenStreetMap | Spatial / POI | Boundaries, roads, amenities | Continuous | Free |
| MD DOT Traffic Counts | Traffic | Movement intensity, seasonal factors | Annual | Free |
| GTFS (Purple Line) | Transit | Boardings, route activity | Per schedule | Free |
| M-NCPPC GIS Layers | Spatial | AOI boundaries, zoning, parks | Client-maintained | Free |
| SafeGraph Patterns | Mobility (sample) | Calibration only | Monthly sample | $500–1,500/mo |