Traverse & closure
Enter bearings and distances — quadrant or azimuth, DMS, decimal, or packed Topcon-style DDD.MMSS — and watch live running coordinates, misclosure, and precision ratio (e.g. 1:12,510) update as you type.
Coordinate geometry that works where you do.
COGO Survey Calculator is a field-ready iOS app for land surveyors: close and balance traverses, solve curves and intersections, subdivide parcels, and hand off CAD-ready files — all completely offline.
iOS 26+ Fully offline No tracking No account
Built for the field
Everything a survey day needs
The full COGO toolkit — from a quick inverse to a balanced boundary traverse, a parcel subdivision, and a CAD handoff — in one offline app.
Curve legs in the traverse
Enter deed calls with circular arcs — chord bearing + radius + arc length + left/right — straight into the leg list. Closure, area, plot, DXF bulges, and the PDF report are all arc-aware.
Compass & Transit adjustment
Balance a traverse by the Bowditch (Compass) or Transit rule for defensible, adjustable records.
Area & inverse
Enclosed area in acres or hectares; inverse between any two points for distance, azimuth, and quadrant bearing. Radiations mode: bearing + distance from one occupied point to every other at once.
Horizontal curve solver
Solve a full circular curve from any two knowns — R, Δ, arc, tangent, chord, E, M, degree of curve — with PC/PT coordinates.
COGO intersections & resection
Bearing–bearing, bearing–distance, distance–distance intersections and 3-point (Tienstra) resection from existing control.
Horizontal alignment
PI-chained tangents with circular curves and clothoid spirals; stationing, coordinate-at-station, station + offset, and stakeout along the alignment.
Traverse plot
Auto-fit sketch with vertex labels, north arrow, scale bar, and a dashed misclosure gap. Tap any point to inspect.
Legal description
Generate a metes-and-bounds deed description from a closed traverse — ready to paste into a legal document.
Area subdivision
Predetermined / hinged area: solve a missing bearing/distance, a parallel cutoff, or a hinged line so a parcel hits a target area.
Coordinates & projections
UTM converter (offline WGS84 ↔ UTM) and State Plane Coordinates SPCS83 (Lambert + Transverse Mercator on GRS80/NAD83) with grid scale factor, convergence, and combined grid↔ground factor.
On-device AI assistant
"Theo" answers questions about your job and drafts traverse legs from plain-English prompts using Apple Foundation Models — entirely on device, nothing leaves your phone.
Complete toolkit
Every tool, at a glance
Field geometry
- 3-point circle / arc fit — center, radius, central angle, arc length, chord, plus equally spaced stake points
- Angle calculator — chain angles with +/− in DMS or packed DDD.MMSS; running total in DMS and decimal
- Station & Offset — station (12+34.56) and perpendicular offset of any point against a reference line
- Grade & slope — rise/run ↔ grade %, slope distance, slope angle, H:V ratio
- Triangle solver — SSS, SAS, ASA, AAS, and ambiguous SSA (both solutions); area and perimeter
- Vertical curve solver — symmetric parabolic profiles: PVC/PVT, K value, high/low point, elevation at any station
Import / export — free for everyone
- CSV import & export with a configurable layout and delimiter — PNEZD, PENZD, NEZ, ENZ … comma, semicolon, tab, or space
- DXF export (AutoCAD R12) — layers, PNEZD labels, polyline traverse with arc bulges, drawing extents
- Single-page PDF survey report
- All exports via the system share sheet — no cables, no desktop app
Onboarding & usability
- First-run tutorial and two one-tap sample jobs — a simple boundary and a six-leg subdivision lot with a curved frontage
- "What these numbers mean" info panel
- Animated, field-friendly numeric keypad
- Fully offline — no account, no network, no tracking, no third-party dependencies
Simple pricing
Free to start. Pro when you need it.
Free covers one job and up to ten points with full on-screen computation — including free CSV, PDF, and DXF export. COGO Pro unlocks unlimited jobs & points, Compass/Transit adjustment, and enclosed-area output.
Monthly
Subscription
auto-renewing, cancel anytime
BEST VALUE
Yearly
Subscription
auto-renewing, best value
Lifetime
One-time
pay once, yours for good
All three plans unlock the same "COGO Survey Calculator Pro" features. Prices are shown in the app in your local currency. Subscriptions are billed through your Apple Account and renew automatically unless cancelled at least 24 hours before the period ends; manage or cancel anytime in Settings. See the Terms of Use.
Your survey data never leaves your device
COGO Survey Calculator does not track you, show ads, or use any third-party analytics. Every job, point, and traverse is stored only on your iPhone or iPad. There is no account and no server — because the app never connects to one.
Read the privacy policy