# Acceptance Criteria Assessment

## Context

Balloon at 10km altitude. AI detection model trained on imagery from 600-1000m altitude (trucks, vehicles, tracked machinery). Goal: reuse model by using a zoom gimbal camera to achieve equivalent Ground Sample Distance (GSD) from 10km. Budget: under $30k.

## Key Technical Analysis

### GSD Requirements

The AI model was trained on 600-1000m imagery. Typical drone cameras at those altitudes produce:

- At 600m: GSD ~5-10 cm/pixel
- At 1000m: GSD ~10-15 cm/pixel

For vehicle detection per NIIRS scale:

- Vehicle detection: ~1m GSD
- Vehicle type identification: ~25-50 cm GSD
- Detailed vehicle description: ~10 cm GSD

Target GSD from 10km: **5-15 cm/pixel** to match training data.

### Required Focal Length from 10km

Formula: `focal_length = (pixel_pitch × altitude) / target_GSD`


| Sensor Type       | Pixel Pitch | Target GSD 15cm | Target GSD 10cm | Target GSD 5cm |
| ----------------- | ----------- | --------------- | --------------- | -------------- |
| 1/2.8" (5MP)      | ~2.0µm      | 133mm           | 200mm           | 400mm          |
| 1/2.3" (25MP)     | ~1.05µm     | 70mm            | 105mm           | 210mm          |
| 1" (20MP)         | ~2.4µm      | 160mm           | 240mm           | 480mm          |
| Full-frame (61MP) | 3.76µm      | 251mm           | 376mm           | 752mm          |


### Atmospheric Resolution Limit

From 10km looking down, atmospheric turbulence limits ground resolution to approximately **4.6 cm** (theoretical, under ideal conditions). Practical limit: **5-8 cm** depending on weather. This means:

- GSD finer than ~5 cm provides no benefit
- 10-15 cm GSD is safely achievable (optics-limited, not atmosphere-limited)

### Environmental Conditions at 10km Altitude

- Temperature: approximately **-50°C**
- Pressure: ~264 hPa (26% of sea level)
- Consumer cameras rated 0°C to 40°C — **will not function without heated enclosure**
- Drone gimbal cameras rated -20°C to +60°C — **still insufficient for -50°C**
- All solutions require thermal management (insulated/heated housing)

## Acceptance Criteria


| Criterion             | Derived Value                                      | Researched Feasibility                                                                                                | Cost/Timeline Impact                              | Status                                         |
| --------------------- | -------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------- | ---------------------------------------------- |
| Budget                | <$30k                                              | Realistic. Good systems $5k-15k, premium $15k-25k including enclosure                                                 | Achievable                                        | Confirmed                                      |
| GSD from 10km         | 5-15 cm/pixel (match training data)                | Achievable with 170-800mm FL depending on sensor. Atmospheric limit ~5cm                                              | Core requirement, drives lens/sensor choice       | Confirmed                                      |
| FOV per frame         | >200m ground width                                 | At 10-15cm GSD with 2000-8000px: 200-1200m width. Acceptable                                                          | No issue with most cameras                        | Confirmed                                      |
| Gimbal stabilization  | 3-axis, ±0.02° or better                           | Standard in $2k-8k gimbal cameras. Balloon needs additional passive stabilization                                     | Balloon motion is the challenge, not gimbal specs | Modified — need passive + active stabilization |
| Image quality for AI  | Must be compatible with model trained at 600-1000m | Atmospheric haze at 10km WILL degrade contrast vs clean 600-1000m imagery. May need dehazing and/or model fine-tuning | Moderate risk — software mitigation possible      | Added                                          |
| Operating temperature | Balloon has thermal protection — not a concern     | User confirmed thermal management is handled                                                                          | No additional cost                                | Removed                                        |
| Weight                | Not critical                                       | Most camera+gimbal systems 1-5kg. Enclosure adds 1-3kg. Total 3-8kg                                                   | Fine for balloon                                  | Confirmed                                      |


## Restrictions Assessment


| Restriction                 | Derived Value           | Researched Feasibility                                                                                                                   | Cost/Timeline Impact             | Status    |
| --------------------------- | ----------------------- | ---------------------------------------------------------------------------------------------------------------------------------------- | -------------------------------- | --------- |
| Balloon platform at 10km    | Fixed constraint        | Unusual altitude — between aerostat (500-3500m) and HAPS (18-20km). Very few purpose-built systems. Must adapt drone/DSLR equipment      | Custom integration required      | Confirmed |
| AI model reuse (no retrain) | Must match training GSD | Feasible for GSD matching. Image quality differences (haze, contrast) may require model fine-tuning or preprocessing                     | Low-moderate risk                | Confirmed |
| Temperature at 10km         | -50°C ambient           | Heated enclosure mandatory. All cameras, gimbals, and batteries need thermal protection. Power budget increases 20-50W for heating       | $2k-5k added, +2-3kg weight      | Added     |
| Pressure at 10km            | ~264 hPa                | Some electronics may need conformal coating or pressurized housing. Lens fogging risk. Most industrial electronics tolerate low pressure | Minor added cost ($500-1k)       | Added     |
| Power at 10km               | Balloon power source    | Camera (10-20W) + gimbal (20-50W) + heating (20-50W) ≈ 50-120W total. Balloon must supply sufficient power                               | Must verify balloon power budget | Added     |
| Atmospheric haze            | 10km air column         | Clear weather (user-specified) helps. Contrast reduction is inevitable. Computational dehazing recommended                               | Software mitigation, low cost    | Added     |


## Key Findings

1. **GSD matching is achievable** within budget. Multiple camera/lens combinations can deliver 5-15 cm/pixel GSD from 10km
2. **Thermal management is the hidden critical requirement**. No commercial camera or gimbal operates at -50°C without protection
3. **Atmospheric degradation is the biggest risk for AI model reuse**. Even with perfect GSD match, image contrast/sharpness will be lower than training data from 600-1000m. Recommend computational dehazing and potential model fine-tuning
4. **Balloon motion stabilization** requires both passive (pendulum damping, suspension design) and active (3-axis gimbal) approaches
5. **Budget is realistic** for mid-range solutions ($8k-20k for camera+gimbal+enclosure) with room for integration costs

## Sources

- NIIRS Civil Reference Guide (irp.fas.org) — GSD requirements for vehicle detection
- Pix4D — GSD calculation methodology
- "Limiting Resolution Looking Down Through the Atmosphere" (Optica) — atmospheric resolution limits
- UAVOS POD specifications — stratospheric camera benchmark (69cm GSD at 15km)
- Airmobi/Viewpro A40 Pro, Z40K — drone gimbal camera specs and pricing
- LoongUAV VT500Rs — high-res zoom gimbal specs
- Sony FE 400-800mm announcement — super telephoto lens specs/pricing
- Gremsy T7 specifications — gimbal payload capacity
- IAState Digital Press — high-altitude balloon payload stabilization research

