Cam IncollFieldwalker's Contour Walker is an offline field tool that guides you along a contour line on the ground — using your phone's GPS and compass to show which way to walk to stay at a constant elevation. You can record the line you walk and save it back onto your map.
There's a technique in permaculture design where you walk a contour line across a paddock, marking it with flags or stakes as you go. The line you walk becomes the guide for a swale, a dam wall, an access track, or any earthwork that needs to follow a constant elevation.
Traditionally, this is done with an A-frame level or a laser level — slow, careful work with physical equipment. You set the level, walk a few metres, check again, adjust, mark, repeat. It works, but it takes time and it takes a level.
Contour Walker does the same thing with your phone.
How it works in the field
You open Contour Walker on your phone while standing on the property. The app shows your aerial map with contour lines overlaid and your live GPS position. You either lock in your current elevation as the target, or tap a spot on the map to choose a different one.
Then you walk.
A compass-style arrow in the centre of the screen shows which way to go. When you're on the contour line, the arrow points straight ahead — keep walking. When you drift uphill, the arrow leans to guide you back down to the target elevation. When you drift downhill, it leans the other way. A colour-coded indicator tells you your status plainly: "On the line," "Drifting off," or "Off the line." There's an audio cue too, so you don't have to stare at the screen while walking uneven ground.
The whole thing runs offline. The elevation data for your area is downloaded once in advance, and all the guidance calculations happen on your phone. No mobile signal required — which matters, because the paddock where you're marking out a swale line is almost certainly the paddock with no reception.
Recording the line you walk
You can record your path as you walk. Tap "Start walk" and a breadcrumb trail appears on the map behind you, tracing the line you've actually followed. When you're done, tap "End & save" and the walked line is saved back onto your map as a real, editable line — the kind you can see later in the desktop editor and use as a reference for earthworks planning.
If you lose GPS signal briefly or need to pause and check something, the recording handles interruptions. You pick up where you left off. And if you were offline when you recorded, the line syncs to the server when you reconnect.
This is the bridge between the design on the screen and the earthwork on the ground. The contour line on your map told you where the swale should go. The walked line confirms it — traced at ground level, at the actual elevation, on the real terrain.
Honest about accuracy
Contour Walker is as accurate as the elevation data it's working from. If your map has high-resolution elevation data — 50cm or better — the guidance is tight and the contour line is reliable enough for earthworks marking. If the elevation data is coarser, the tool tells you: a warning banner explains the DEM resolution and suggests upgrading to sourced high-resolution data for better accuracy.
GPS accuracy matters too. In open paddock with clear sky, phone GPS is typically within a few metres — good enough for marking a rough contour line that you'll refine with surveying equipment or a laser level before final earthworks. In heavy tree cover or near buildings, GPS drifts more. The tool shows your GPS accuracy and flags when the signal is weak.
This isn't a replacement for a surveyor on precision earthworks. It's a tool that lets you walk a contour line quickly, mark the general path, and record it on your map — so when the surveyor or the earthworks contractor arrives, you've already done the design thinking and you're pointing them at a specific line on the ground, not a general area.
Why this matters for permaculture
In the Yeomans framework, water management starts with understanding how water moves across the land. Contour lines are the foundation of that understanding. And the critical step — the one that turns a line on a map into an earthwork on the ground — is walking that contour in the field.
Contour Walker makes that step faster and more accessible. You don't need an A-frame or a laser level. You don't need a second person holding the other end. You walk, the phone guides you, and the line you trace becomes part of your permanent site record.
The contour moves from the screen to the soil. And that's where the design starts to become real.