What OpenSurvey3D does

A free survey and GIS field app for iPhone and iPad. It works with the phone's own GPS and reaches centimetre accuracy with an RTK receiver.

On this page

OpenSurvey3D is a field app for collecting and checking positions: points, lines and areas on a map. Each one keeps an audit trail of how it was measured. It works with the GPS already in your phone. When you connect a GNSS receiver and a correction source, it records centimetre-grade positions.

There is no account and no subscription. Everything you collect stays on your device until you export it.

What you can do with it

  • Collect points, lines and areas, each with a feature code, typed attributes, notes and photos.
  • Average a point over many samples, or let auto capture save a point on a timer as you walk.
  • Connect a GNSS receiver over Bluetooth or Wi-Fi, and pull RTK corrections from an NTRIP caster or a state CORS network.
  • Work in your coordinate system. 455 zones are built in: every NAD83 state plane and UTM zone, plus WGS 84 and ETRS89 UTM, with display in metres, feet or US survey feet.
  • Stake out any asset or imported design point, and check your work against a known point.
  • Run COGO in the field: inverse, traverse with closure, intersections, curves, and cut and fill against a design surface.
  • See the site in 3D on real terrain, and capture in 3D with LiDAR point clouds or Object Capture photogrammetry.
  • Find assets in AR through the camera.
  • Import deed and design data (CSV, PNEZD, GeoJSON, DXF, LandXML, GeoPackage, Shapefile, GPX, KML).
  • Export CSV, PNEZD, GeoJSON, DXF, LandXML, GeoPackage, Shapefile, LAS and a complete ZIP bundle, plus a QA report as a PDF.
  • Work offline with downloaded map areas.

A typical job

A survey job runs from setting up the project to handing files to the office:

Diagram: a typical job in seven steps: create a project and choose its zone, connect the receiver and corrections, check a known point, collect points, lines and areas, review the QA report, export the bundle, and open it in CAD and GIS in the office.
From the field to the office. Every step has its own guide in these docs.

Requirements

You need For
iPhone or iPad with iOS 26.2 or later Everything
Nothing else Collecting, stakeout, COGO, the 3D site model, imports and exports, using the built-in GPS
A GNSS receiver plus a correction source (NTRIP caster or CORS login) Centimetre-grade positions
iPhone Pro or iPad Pro (LiDAR scanner) LiDAR point-cloud capture
A device that supports Object Capture Photo-scan (photogrammetry) capture
An internet connection, at least once Map tiles, terrain and NTRIP corrections. Download offline maps before you head out.

Supported receivers over Bluetooth are Emlid Reach RX, RX2 and RS4, and Bad Elf Flex and Flex Mini. Over Wi-Fi, the app works with any receiver that streams NMEA over TCP, such as an Emlid Reach RS2 in hotspot mode.

How accurate is it?

It depends on the position source, and the app always tells you which one it's using:

  • Phone GPS alone: typically 3 to 5 metres horizontally, and much worse vertically. That's fine for GIS inventory and for finding things again. It isn't survey-grade.
  • A receiver with RTK corrections (RTK fixed): centimetre-grade, as reported by the receiver's own error statistics.

The accuracy pill at the top right of the screen shows the current source and accuracy at all times. Every saved position keeps a full record of how it was measured.

Diagram: four levels of position quality, from phone GPS at 3 to 5 metres to RTK fixed at centimetre level, with what the accuracy pill reads at each.
What the accuracy pill reads at each level of position quality.

Where your data lives

Projects, photos and scans are stored on the device. The app has no cloud sync and no analytics. Data leaves the device only when:

  • you export or share something;
  • you connect to an NTRIP caster, which receives your approximate position so it can send corrections;
  • you send a problem report from inside the app, which includes only what the form shows you.

Open source

OpenSurvey3D is MIT licensed and built by Laan Labs, the studio behind 3D Scanner App.