Graham McIntire
a283ad9c66
QSO enrichment now groups all path points by HRRR hour and creates one batch job per hour instead of one job per point. The batch job downloads the GRIB2 data once and extracts all needed points from the same binary. Legacy single-point jobs are still supported for backward compatibility.
579 lines
16 KiB
Markdown
579 lines
16 KiB
Markdown
# Comprehensive Propagation Algorithm Documentation
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## Overview
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The ntms-proptools suite consists of three interconnected applications for mm-wave (24/47 GHz) propagation analysis and prediction. All share common physics algorithms calibrated against confirmed radio contacts.
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**Calibration Contacts:**
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- 47 GHz Jun 01 2024 98.8 km (09:00 CDT)
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- 47 GHz Nov 01 2025 116.0 km (07:44 CST)
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- 24 GHz Nov 01 2025 101.0 km (07:54 CST)
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- 24 GHz Sep 07 2002 542.1 km (longest, 07:35 CDT)
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---
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## PART 1: PROP-CAST (Real-Time Station Scoring)
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### Purpose
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Live multi-station propagation scoring across ~500-mile DFW radius using current ASOS observations.
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### Data Inputs
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**Surface Observations (ASOS/NWS):**
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- Temperature (°F → °C conversion: `(tF - 32) * 5/9`)
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- Dew point (°F → °C)
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- Relative humidity (%)
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- Wind speed (knots → m/s: `knots * 1.15078`)
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- Wind direction (degrees)
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- Sea-level pressure (hPa)
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- Altimeter setting (inches Hg → hPa: `inches * 33.8639`)
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- Cloud cover (categorical: CLR, FEW, SCT, BKN, OVC, VV)
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**Frequency Configurations:**
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```javascript
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// 47 GHz Configuration
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47: {
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label: "47 GHz",
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accentHex: "#00ffa3",
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attenPerKm: (rho) => 0.006 * rho + 0.040,
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humPenalty: 1.0,
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seasonAdj: { 6:-0, 7:-0, 8:-0, 5:-0, 9:-0 },
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// Atmospheric window: between 22.235 GHz H₂O peak and 60 GHz O₂ peak
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}
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// 24 GHz Configuration
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24: {
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label: "24 GHz",
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accentHex: "#44ddff",
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attenPerKm: (rho) => 0.0067 * rho + 0.006,
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humPenalty: 1.6,
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seasonAdj: { 6:-8, 7:-10, 8:-10, 5:-4, 9:-4 },
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// Adjacent to 22.235 GHz H₂O absorption line shoulder
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}
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```
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### Physics Calculations
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#### 1. Absolute Humidity Calculation
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```javascript
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function absHumidity(rhPct, tempC) {
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// Magnus formula for saturation vapor pressure
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const es = 6.112 * Math.exp((17.67 * tempC) / (tempC + 243.5));
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// Absolute humidity in g/m³
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return (217 * (rhPct/100) * es) / (tempC + 273.15);
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}
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```
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**Formula:** ρ = 217 * (RH/100) * e_s / T
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- RH: relative humidity (%)
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- e_s: saturation vapor pressure (hPa) via Magnus formula
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- T: absolute temperature (K)
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- Result: ρ in g/m³
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#### 2. Gaseous Absorption by Frequency
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```javascript
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attenPerKm(rho) = O₂_coefficient + H₂O_coefficient * rho
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```
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**47 GHz:** 0.040 + 0.006·ρ dB/km
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- O₂ component: ~0.040 dB/km (from 60 GHz O₂ line wing)
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- H₂O component: ~0.006·ρ dB/km (22.235 GHz H₂O line wing)
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**24 GHz:** 0.006 + 0.0067·ρ dB/km
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- O₂ component: ~0.006 dB/km
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- H₂O component: ~0.0067·ρ dB/km (stronger H₂O sensitivity on 22.235 GHz shoulder)
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### Scoring Functions
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All return 0-100 scale representing propagation favorability.
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#### Score: Humidity
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```javascript
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function scoreHumidity(rho, freq) {
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const r = rho * FREQ_CONFIG[freq].humPenalty;
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if (r <= 6) return 100;
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if (r <= 9) return 95 - ((r-6)/3) * 20;
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if (r <= 13) return 75 - ((r-9)/4) * 30;
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if (r <= 18) return 45 - ((r-13)/5) * 35;
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return Math.max(0, 10 - (r-18)*2);
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}
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```
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**Penalty Factor per Frequency:**
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- 47 GHz: multiplier = 1.0
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- 24 GHz: multiplier = 1.6 (more sensitive due to H₂O line proximity)
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**Thresholds:**
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- r ≤ 6: Score 100 (dry/excellent)
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- r ≤ 9: Linear decay from 95 → 75 (excellent → good)
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- r ≤ 13: Linear decay from 75 → 45 (good → marginal)
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- r ≤ 18: Linear decay from 45 → 10 (marginal → poor)
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- r > 18: Score 0 (very humid/negligible)
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#### Score: Wind Speed
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```javascript
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function scoreWind(mph) {
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if (mph < 2) return 100;
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if (mph < 5) return 90;
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if (mph < 9) return 72;
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if (mph < 14) return 42;
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if (mph < 20) return 16;
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return 0;
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}
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```
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**Rationale:** Wind causes mechanical mixing of boundary layer, destroying temperature inversion. Still air promotes stable inversion.
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#### Score: Sky Cover
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```javascript
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function scoreSky(c) {
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return ({
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CLR: 100, SKC: 100,
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FEW: 88,
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SCT: 60,
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BKN: 25,
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OVC: 5, VV: 5
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})[c] ?? 50;
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}
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```
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**METAR Cloud Cover Legend:**
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- CLR/SKC: Clear (100)
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- FEW (1/8–2/8): 88
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- SCT (3/8–4/8): 60 (scattering)
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- BKN (5/8–7/8): 25 (broken)
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- OVC (8/8): 5 (overcast)
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- VV (vertical visibility): 5
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#### Score: Season (Month-Based)
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```javascript
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function scoreSeason(month, freq) {
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const b = ({
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1:88, 2:84, 3:72, 4:62, 5:55,
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6:42, 7:28, 8:28, 9:52, 10:68,
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11:96, 12:88
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})[month] ?? 50;
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return Math.max(0, Math.min(100, b + FREQ_CONFIG[freq].seasonAdj[month]??0));
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}
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```
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**Base Monthly Scores:**
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- Peak: November (96), December (88), January (88)
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- Summer worst: July/August (28)
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- 24 GHz additional penalties: June (-8), July (-10), August (-10), May (-4), September (-4)
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**Rationale:** Seasonal humidity variation; summer monsoon moisture increases H₂O absorption.
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#### Score: Time of Day (Inversion-Based)
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```javascript
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function scoreTimeOfDay(utcH, utcM, month) {
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const isCDT = month >= 3 && month <= 10;
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const local = (utcH + utcM/60 + (isCDT ? -5 : -6) + 24) % 24;
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const sr = [7.4,7.3,7.0,6.7,6.35,6.25,6.35,6.65,6.9,7.1,7.35,7.45][month-1];
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const d = local - sr; // hours relative to sunrise
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if (d >= -0.5 && d <= 1.5) return {s:100, lbl:"Peak — inversion maximum"};
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if (d > 1.5 && d <= 3.0) return {s:78, lbl:"Good — inversion eroding"};
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if (d > -1.5 && d < -0.5) return {s:82, lbl:"Pre-sunrise — building"};
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if (d > 3.0 && d <= 6.0) return {s:38, lbl:"Marginal — BL mixing"};
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if (local >= 21 || local <= 3) return {s:68,lbl:"Overnight — cooling"};
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if (d > 6.0) return {s:18,lbl:"Afternoon — duct unlikely"};
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return {s:48,lbl:"Early morning"};
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}
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```
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**Window Tiers:**
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1. **Peak Window** (sunrise -30min to +1.5h): Score 100 — Inversion maximum strength
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2. **Good Window** (+1.5h to +3h after sunrise): Score 78 — Inversion still present but eroding
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3. **Pre-Sunrise** (-1.5h to -30 min): Score 82 — Inversion building under clear skies
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4. **Marginal Window** (+3h to +6h after sunrise): Score 38 — Convective boundary layer growth
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5. **Overnight Cooling** (21:00 to 03:00 local): Score 68 — Weak inversion reformation
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6. **Afternoon** (+6h after sunrise): Score 18 — Full convective mixing, inversion destroyed
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**Sunrise Lookup Table (Monthly, local decimal hours):**
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```
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Jan:7.4 Feb:7.3 Mar:7.0 Apr:6.7 May:6.35 Jun:6.25
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Jul:6.35 Aug:6.65 Sep:6.9 Oct:7.1 Nov:7.35 Dec:7.45
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```
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#### Score: Temperature-Dew Point Depression
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```javascript
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function scoreTdDep(tF, tdF) {
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const d = tF - tdF;
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if (d > 22) return 96;
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if (d > 14) return 80;
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if (d > 8) return 60;
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if (d > 4) return 38;
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return 18;
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}
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```
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**Rationale:** Large Td depression indicates dry air above surface, favorable for stable stratification.
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**Thresholds (°F):**
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- >22°F: 96 (very dry aloft)
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- >14°F: 80 (good stability)
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- >8°F: 60 (moderate)
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- >4°F: 38 (marginal)
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- ≤4°F: 18 (humid aloft)
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#### Score: Pressure Tendency
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```javascript
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function scorePressure(mb, prev) {
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if (prev == null) return 58;
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const d = mb - prev;
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if (d > 2.5) return 98; // Rising pressure → anticyclone → stable
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if (d > 0.8) return 82;
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if (d > -0.5) return 60;
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if (d > -2.0) return 32;
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return 10; // Falling pressure → cyclone → unstable
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}
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```
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### Composite Propagation Score
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```javascript
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function composite(f) {
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return Math.round(
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f.humidity * 0.26 +
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f.wind * 0.18 +
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f.sky * 0.15 +
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f.timeOfDay * 0.14 +
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f.tdDep * 0.11 +
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f.season * 0.09 +
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f.pressure * 0.07
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);
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}
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```
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**Weights:**
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| Factor | Weight | Importance |
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|--------|--------|------------|
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| Humidity | 26% | Most critical (absorption) |
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| Wind | 18% | Destroys inversion |
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| Sky | 15% | Less impact than humidity |
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| Time of Day | 14% | Inversion strength varies |
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| Td Depression | 11% | Aloft stability |
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| Season | 9% | Long-term trend |
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| Pressure | 7% | Weak indicator |
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**Total: 100%**
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### Scoring Tiers
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| Score | Band | Label | Hex |
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|-------|------|-------|-----|
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| 80-100 | EXCELLENT | Green/cyan | #00ffa3 |
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| 65-79 | GOOD | Light cyan | #7dffd4 |
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| 50-64 | MARGINAL | Yellow | #ffe566 |
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| 33-49 | POOR | Orange | #ff9044 |
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| 0-32 | NEGLIGIBLE | Red | #ff4f4f |
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---
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## PART 2: PROP-ANALYZER (Historical Contact Analysis)
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### Purpose
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Analyze atmospheric conditions (ASOS + Skew-T sounding) during historical radio contacts to identify propagation mechanisms.
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### Additional Physics Calculations
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#### Refractivity Profile (Modified N-Units)
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```javascript
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// Saturation vapor pressure (Buck equation)
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function satVapPres(tC) {
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return 6.1121 * Math.exp((18.678 - tC/234.5) * (tC/(257.14 + tC)));
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}
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// N-unit profile (ITU-R P.453-14)
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const N = 77.6 * P/T + 3.73e5 * e / (T * T)
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// M-unit profile (accounts for earth curvature)
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const M = N + 0.157 * (hght - sfc_hght)
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```
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**Where:**
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- P: pressure (hPa)
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- T: absolute temperature (K)
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- e: water vapor pressure (hPa) = satVapPres(Td)
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- h: height MSL (m)
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- sfc_hght: surface height MSL (m)
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#### Duct Detection via M-Profile
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**Definition:** A duct exists where dM/dh < 0 (M decreases with height)
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```javascript
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const ducts = [];
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let inDuct = false, ductBase = null, ductBaseM = null;
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for (let i = 1; i < refractProfile.length; i++) {
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const dM = refractProfile[i].M - refractProfile[i-1].M;
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if (dM < 0 && !inDuct) {
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inDuct = true;
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ductBase = refractProfile[i-1].hAGL;
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ductBaseM = refractProfile[i-1].M;
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} else if (dM >= 0 && inDuct) {
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inDuct = false;
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const top = refractProfile[i-1].hAGL;
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const strength = ductBaseM - refractProfile[i-1].M;
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if (strength > 2) { // Filter: only significant ducts
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ducts.push({ base: ductBase, top, strength: strength.toFixed(1) });
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}
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}
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}
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```
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**M-Unit Gradient Interpretation:**
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- dM/dh < -157 /km: Super-refractive (ducting probable)
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- dM/dh < -79 /km: Enhanced refraction (extended range)
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- dM/dh > 0: Sub-refractive (reduced range)
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- dM/dh ≈ -40 /km: Standard atmosphere
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#### Inversion Detection
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```javascript
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const inversions = [];
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for (let i = 1; i < sorted.length; i++) {
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if (sorted[i].tmpc > sorted[i-1].tmpc) { // Temperature increases with height
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inversions.push({
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base: sorted[i-1].hght - sfc.hght,
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top: sorted[i].hght - sfc.hght,
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strength: sorted[i].tmpc - sorted[i-1].tmpc, // °C
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rate: strength / ((top - base) / 100) // °C per 100m
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});
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}
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}
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// Merge adjacent inversions within 200m gap
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// Keep only meaningful: strength >= 0.5°C and base < 5000m
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```
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#### Stability Indices
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**K-Index:**
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```javascript
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const kIndex = (T850 - T500) + Td850 - (T700 - Td700)
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```
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**Lifted Index (Simplified):**
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```javascript
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const li = T500 - (Tsfc - (p500_hght - sfc_hght) * 0.00976)
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```
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- LI < 0: Unstable (convection likely)
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- LI > 0: Stable (inversion maintained)
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**Precipitable Water:**
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```javascript
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PW = Σ [(MR_i + MR_{i-1})/2 * ΔP / (9.81 * 10)]
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// MR = mixing ratio = 622 * e / (P - e)
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```
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#### Boundary Layer Depth
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```javascript
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// Potential temperature
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theta = T + (9.8 * h / 1000)
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// Find height where theta > theta_sfc + 2°C
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```
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---
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## PART 3: LINK BUDGET ANALYZER (Point-to-Point Path Analysis)
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### Purpose
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Complete point-to-point RF link analysis including path clearance, Fresnel zone obstruction, and margin calculations.
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### Path Geometry
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**Maidenhead Grid Decode:** Field (20°×10°) → Square (2°×1°) → Subsquare (5'×2.5') → Extended
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**Distance:** Great-circle haversine
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### Path Clearance Physics
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#### Fresnel Zone Radius
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```javascript
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function fresnelRadius(d1m, d2m, lambdaM) {
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return Math.sqrt(lambdaM * d1m * d2m / (d1m + d2m));
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}
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// λ = 0.3 / f_GHz
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```
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#### Earth Bulge Correction
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```javascript
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function earthBulge(frac, distKm, K = 4/3) {
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const d1 = frac * distKm * 1000;
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const d2 = (1 - frac) * distKm * 1000;
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return (d1 * d2) / (2 * K * 6371000);
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}
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```
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**Effective K-factor from Surface Refractivity:**
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```javascript
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function effectiveKFactor(N_surface) {
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const N_std = 315;
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const dN_std = -40;
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const dN_est = dN_std - (N_surface - N_std) * 0.25;
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const Ke = 1 / (1 + 6371 * dN_est * 1e-6);
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return Math.max(0.5, Math.min(5.0, Ke));
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}
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function surfaceRefractivity(tC, rhPct, mslpHpa) {
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const T = tC + 273.15;
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const P = mslpHpa ?? 1013.25;
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const es = 6.112 * Math.exp(17.67 * tC / (tC + 243.5));
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const e = (rhPct / 100) * es;
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return (77.6 * P / T) + (3.73e5 * e / (T * T));
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}
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```
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#### Knife-Edge Diffraction
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```javascript
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function knifeEdgeLoss(v) {
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if (v <= -0.7787) return 0; // Clear
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if (v <= 0) return -20 * Math.log10(0.5 - 0.62 * v);
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if (v <= 1) return -20 * Math.log10(0.5 * Math.exp(-0.95 * v));
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if (v <= 2.4) {
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const inner = Math.max(0, 0.1184 - (0.38 - 0.1 * v) ** 2);
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return -20 * Math.log10(0.4 - Math.sqrt(inner));
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}
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return 20 * Math.log10(v) + 13.0; // Asymptotic
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}
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```
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**Diffraction Verdicts:**
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- v < -0.7787: CLEAR (0 dB loss)
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- -0.7787 < v < 0: FRESNEL_MINOR (< 3 dB)
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- 0 < v < 2.4: FRESNEL_PARTIAL (3-10 dB)
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- v > 2.4: BLOCKED (>10 dB)
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|
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### RF Link Budget
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#### Free-Space Path Loss (ITU-R P.525)
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```javascript
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function fspl(distKm, fGhz) {
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return 20 * Math.log10(distKm) + 20 * Math.log10(fGhz) + 92.45;
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}
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```
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#### Gaseous Absorption (ITU-R P.676)
|
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```javascript
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function gasLoss(distKm, rhoGm3, freq) {
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return (cfg.o2dBkm + cfg.h2oCoeff * rhoGm3) * distKm;
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}
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```
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| Frequency | O₂ (dB/km) | H₂O Coeff | Notes |
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|-----------|-----------|-----------|-------|
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| 47 GHz | 0.040 | 0.006 | Clear window |
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| 24 GHz | 0.006 | 0.0067 | H₂O shoulder |
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| 10 GHz | 0.003 | 0.0005 | Clear window |
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|
||
#### EIRP
|
||
```javascript
|
||
eirp = pDbm + gtxDbi - feedDb
|
||
```
|
||
|
||
#### Receiver Sensitivity
|
||
```javascript
|
||
sensitivity = -174 + nfDb + 10 * Math.log10(bw)
|
||
// CW: bw=500 Hz, SSB: bw=2700 Hz
|
||
```
|
||
|
||
#### Duct Enhancement Estimate
|
||
```javascript
|
||
function ductEnhancement(propScore) {
|
||
if (propScore >= 80) return -14; // 14 dB improvement
|
||
if (propScore >= 65) return -10;
|
||
if (propScore >= 50) return -6;
|
||
if (propScore >= 33) return -2;
|
||
return 0;
|
||
}
|
||
```
|
||
|
||
Calibrated against confirmed contacts.
|
||
|
||
### Success Probability
|
||
|
||
```javascript
|
||
function marginToSuccess(marginDb, propScore) {
|
||
// Margin factor (piecewise linear)
|
||
let marginPct;
|
||
if (marginDb <= 0) marginPct = 0;
|
||
else if (marginDb <= 10) marginPct = (marginDb / 10) * 20;
|
||
else if (marginDb <= 15) marginPct = 20 + ((marginDb - 10) / 5) * 20;
|
||
else if (marginDb <= 20) marginPct = 40 + ((marginDb - 15) / 5) * 20;
|
||
else if (marginDb <= 25) marginPct = 60 + ((marginDb - 20) / 5) * 20;
|
||
else if (marginDb <= 30) marginPct = 80 + ((marginDb - 25) / 5) * 20;
|
||
else marginPct = 100;
|
||
|
||
// Propagation factor (±30% modulation)
|
||
const propFactor = 0.70 + (propScore / 100) * 0.60;
|
||
|
||
return Math.max(0, Math.min(99, Math.round(marginPct * propFactor)));
|
||
}
|
||
```
|
||
|
||
**Margin → Success Calibration:**
|
||
- 0 dB → 0%, 10 dB → 20%, 15 dB → 40%, 20 dB → 60%, 25 dB → 80%, 30+ dB → 100%
|
||
|
||
**Propagation Modulation:**
|
||
- Score 100 (excellent): ×1.30
|
||
- Score 50 (neutral): ×1.00
|
||
- Score 0 (poor): ×0.70
|
||
|
||
---
|
||
|
||
## Integration: Data Flow
|
||
|
||
```
|
||
Weather Data (ASOS/NWS)
|
||
↓
|
||
[PropCast] → Composite Score 0-100
|
||
↓
|
||
├→ Real-time station dashboard
|
||
└→ Input to LinkBudget (propScore parameter)
|
||
|
||
Sounding Data (IEM RAOB)
|
||
↓
|
||
[PropAnalyzer] → Refractivity profiles, ducts, inversions
|
||
↓
|
||
├→ Skew-T visualization
|
||
├→ dN/dh gradient analysis
|
||
└→ Mechanism identification
|
||
|
||
Path Geometry + Elevation
|
||
↓
|
||
[LinkBudget] → Profile analysis, Fresnel zones, clearance
|
||
↓
|
||
├→ Diffraction loss calculation
|
||
├→ Link margin = RX Power - Sensitivity
|
||
└→ Success % = marginToSuccess(margin, propScore)
|
||
```
|
||
|
||
---
|
||
|
||
## Constants & Thresholds Reference
|
||
|
||
| Constant | Value | Source |
|
||
|----------|-------|--------|
|
||
| Humidity penalty 47 GHz | 1.0 | Minimal H₂O line sensitivity |
|
||
| Humidity penalty 24 GHz | 1.6 | Adjacent 22.235 GHz H₂O peak |
|
||
| Duct M-unit min depth | 2 | Noise filter |
|
||
| Inversion min strength | 0.5°C | Below is noise |
|
||
| Inversion height limit | 5000m AGL | Above irrelevant |
|
||
| Earth radius | 6371 km | WGS-84 mean |
|
||
| Standard K-factor | 4/3 | Standard atmosphere |
|
||
| Standard surface N | 315 | ITU-R P.453 |
|
||
| Standard dN/dh | -40 /km | ITU-R P.453 |
|
||
|
||
## ITU-R References
|
||
- P.453-14: Radio refractivity
|
||
- P.525: Free-space path loss
|
||
- P.676: Gaseous absorption
|
||
- P.526: Diffraction
|