Methodology

How the Reality Gap is calculated

Every HikingSpecs verdict is a physics calculation, not an opinion. We model how much usable energy a device’s battery actually delivers under field conditions, compare it to the manufacturer’s marketed GPS endurance, and report the difference as the Reality Gap. This page documents the formula, the reference scenario behind our device dossiers, and why we do not yet claim a confirmed field validation.

The formula

Effective capacity is nominal capacity reduced by two physical effects, cycle aging and cold-temperature derating, then drawn down by the device’s total power consumption over time:

C_thermal = C_nom · α_cycle · e^(-k · (T_ref - T_case))
blackout_eta = C_thermal / P_total
reality_gap  = (marketing_claim - blackout_eta) / marketing_claim

The thermal term derates capacity as the cell cools; k is a chemistry-specific coefficient (lithium-cobalt fades faster in cold than LiFePO4). Case temperature is modelled from ambient temperature, wind, and the case material’s thermal conductivity: titanium sheds heat faster than polymer, running the cell colder. Power draw is the sum of idle, GPS-mode, display, and backlight consumption. The full machine-readable specification lives at /formula/v1.0.json.

The reference scenario

Reality Gap depends on conditions, so every device dossier is computed against one fixed, published reference scenario, a demanding but realistic mountain day:

• Ambient temperature: 5 °C
• Wind: 3 m/s
• GPS mode: multi-band (dual-frequency, no SatIQ)
• Sunlight: 10,000 lux (overcast/shade, below the 50,000 lux sunlight threshold)
• Duration: 12 h · Backlight: 4 activations/h · Cell age: 100 cycles

Because the scenario is fixed and published, anyone can reproduce our numbers from the formula. That is the point: the Reality Gap is a measurement, not a marketing line.

Field validation: none yet

Formula v1.0 has no confirmed field validation. The model is calibrated but not independently verified against measured runtime. Existing reviews measure GPS accuracy and drain in mild conditions, not runtime-to-zero in cold and wind, which is exactly what this model predicts. Our first validation will come from a controlled measurement on a known device variant, not from reinterpreting third-party reviews.

What we do not yet claim

Honesty is the brand. We make no claim that Formula v1.0 has been validated against field data, in any temperature range. The extreme-cold tail of the curve (sub-zero, high-wind expedition conditions) is likewise physically modelled but not independently confirmed. We report all figures as model output, and we will publish validations as like-for-like field data becomes available.

Per-device hardware inputs are modeled, not measured. Nominal capacity is documented from a teardown source for one device and derived or estimated for the rest, with provenance unverified for most. Display power is a calibrated estimate, and the AMOLED devices added after the original dataset share a single baseline figure rather than per-device measurements. These inputs reproduce consistently inside the model, but they are engineering estimates, not bench results.

Formula v1.0 · Reality Gap = (marketing claim − calculated blackout) / marketing claim. All figures derived from the published reference scenario and the open formula specification.