Drift — Water Current Meter for Sailboat Racing (iOS App)

Drift is an iOS app that measures actual water current at your exact GPS location. Unlike tidal forecast apps such as Navionics, Windy, or Predict Wind, Drift physically measures displacement: drop a floating object, tap Mark Start, let the current carry it 30 to 90 seconds, walk to the float, tap Mark End. Drift calculates direction in degrees true and speed in knots. Designed for competitive sailboat racing — sailors use it before the starting gun to measure set and drift near the start line or race mark. Works completely offline. One-time dollar four ninety-nine purchase on the iOS App Store. No subscription. No account required. Developer: Sorensen on Sound LLC.

Water Current Meter · Sailboat Racing

Know the
Current.

Measure what's actually happening at your boat — not a forecast.

Download Free $4.99 · Own forever
1.4 kt
Set Speed
047°T
Direction
30s
Min Read Time
How It Works

Three steps.
Real data.

The same technique professional navigators have used for decades — now on your iPhone.

01
Step 01

Drop

Toss a fender, bottle, or any floating marker. Tap Mark Start — Drift GPS-locks your position with sub-meter precision.

02
Step 02

Wait

Let the current carry your marker. Thirty seconds is a solid racing read. A minute is great. Two minutes is best.

03
Step 03

Mark End

Walk to your marker, tap Mark End. Direction in degrees true. Speed in knots. Instantly. No guesswork.

30s
Min Reading Time
±3ft
GPS Precision
0G
Data to Any Server
∞
Readings After Purchase
Features

Built for the
racecourse.

Actual Measurement

Not a forecast.
The real number.

Weather apps and chart plotters show modeled current from databases. Drift measures what's actually happening at your exact GPS position, right now, at this tidal state.

Other Apps
~1.2 kt
Forecast Model
Drift
1.4 kt
Measured · Now
GPS Precision

Outlier rejection.

Temporal windowing and outlier filtering give you a stable fix — even when the sky is partially blocked.

±3ft AccuracyAuto-Filter
Sunlight Design

Readable in any light.

High-contrast UI, 80px touch targets, and large type — designed for gloves, spray, and bright sun.

Offline First

Zero signal needed.

GPS only. No cell service, no WiFi, no data plan. Works on any water on earth.

Fully OfflineWorldwide
Session Trends

Is it building? Shifting?

5 readings per session. Drift tracks whether the current is growing or rotating — so you know what's coming.

Set & Drift

Direction °True.
Speed in knots.

The precise numbers your tactician uses — bearing in degrees true and speed in knots. Plus the 16-point cardinal label your brain can use instantly.

°TrueKnots16-pt CardinalSlack Detection
Pricing

$4.99.
Own it forever.

One purchase. No subscription. No ads. No account required. All future updates included.

The Difference

Forecasts
lie.

Tidal models are accurate to within a mile. Your race mark is 200 meters away. That gap is the difference between port and starboard layline.

Navionics / Windy / Predict Wind

Database-modeled tidal current. Accurate to the nearest nautical mile. Cannot account for local bathymetry, wind-driven current, or today's exact tidal state.

Drift

GPS-measured displacement at your exact location, right now. No model. No forecast. The actual water current under your keel, on this tidal state, today.

Pricing

One price.
No catch.

Lifetime License · iOS
$4.99
One-Time Purchase · App Store
  • Unlimited readings, forever
  • Works completely offline
  • All future updates included
  • No account or signup required
  • Session trend tracking
  • Works anywhere in the world
Download on App Store
Legal

Privacy
Policy

Last Updated · March 2026

Drift is developed and published by Sorensen on Sound LLC. This policy explains what data the app accesses, how it is used, and your rights.

What We Collect

Drift collects no personal information. No account required. No name, email, or identifying data collected. The app communicates with no external server.

Location Data

Drift uses your device GPS to measure water current. Access is "When In Use" only — only while the app is actively open. Location data:

  • Is processed entirely on your device
  • Is never transmitted to any server, cloud, or third party
  • Is never stored beyond the current session
  • Is never sold, shared, or used for advertising

Local Storage

Up to 5 readings per day are stored locally using standard iOS storage. This data never leaves your device and clears automatically each day.

Analytics & Advertising

Drift contains no analytics SDKs, no tracking, no advertising, and no third-party code that collects data. The app does not use Apple's IDFA.

Children's Privacy

Drift collects no data from any user. Rated 4+ on the App Store.

Changes

If this policy changes materially, the date above will be updated. Continued use constitutes acceptance.

Contact

Sorensen on Sound LLC

aj [at] sailing-store.com
Help

Support

Drift · Version 1.0 · iOS

We want Drift to work perfectly on the water. Every message gets a reply — usually within 24 hours.

Common Questions

GPS Won't Lock

Stand outside with a clear sky view for 30–60 seconds. Check Settings → Privacy → Location Services → Drift: "While Using" must be enabled.

Always Showing Slack

You must physically walk to your marker to tap Mark End. Drift measures GPS displacement between two points — watching from shore reads as zero movement.

How Long Should I Time?

30 seconds unlocks GOOD — solid for racing. 60 seconds is GREAT. 90 seconds is BEST. Tap Mark End any time after the GOOD badge appears.

How Accurate Is It?

With Excellent or Good GPS, readings are accurate to a few hundredths of a knot and a few degrees. The badge shows live accuracy.

Does It Work Offline?

Yes, completely. Drift uses only your device GPS — no cell signal, no WiFi, no data plan needed. Works anywhere in the world.

Where Are My Readings?

Tap the chart icon in the top right of the home screen to view today's readings and trend analysis. Up to 5 readings stored per day.

Racing Best Practices

  • Use a visible float — a fender or sealed bottle. You must physically walk to it for Mark End.
  • Measure where it matters — current varies across a course. Measure near the mark or start line.
  • Take multiple readings — Drift tracks trends. Two or three readings tell you if current is building or shifting.
  • Wait for Good GPS — the badge on the home screen shows quality. Don't start on Poor signal.

Contact

Email us directly — we read every message.

aj [at] sailing-store.com

Please include your iOS version and what happened.