How to open a .12da or .12daz file without 12d Model

A .12da file is a 12d Model ASCII archive, a plain-text export of civil design and survey data, and a .12daz file is the same archive zipped. To open one without 12d Model, use the free 12d View to look at it, or a free browser converter to turn it into DXF or LandXML for AutoCAD, BricsCAD, Civil 3D or QGIS.

It usually arrives as a line in an email: "12d data attached." The surveyor or the road designer has done the right thing and issued their model, and now there's a .12daz file sitting in your inbox. If you run 12d Model, you drag it in and get on with your day. If you don't, Windows doesn't know what to do with it and double-clicking it does nothing useful.

This comes up constantly for geotechnical engineers, structural engineers, builders, project managers and smaller civil consultancies. 12d Model dominates civil design and survey in Australia, but a licence costs serious money, and plenty of people who need to read 12d data have no reason to produce it.

What a .12da file is

A .12da file is a 12d Model ASCII archive, the standard way surveyors and civil designers in Australia hand over project data. Two properties make it unusual, and both work in your favour:

It's plain text. Unlike DWG or DGN, a 12d archive is a readable, structured text format. 12d Solutions publish the format specification openly, which is why tools other than 12d Model can be built to read it.

It's an exchange format, not the project. A 12d Model project is a folder of binary working files. The .12da is what you get when someone deliberately exports data out of that project to send to someone else, so it is always a snapshot of what the sender chose to share, never the live project.

The format began life as 12d's .4d ASCII format and was renamed to the .12da extension around 1999.

What a .12daz file is

A .12daz is exactly the same archive, compressed in a ZIP container. Text compresses extremely well, so a 30 MB .12daz can be close to a gigabyte of text once expanded. That's worth knowing before you open one on a modest laptop, and it's why a file that looks small can bring a viewer to its knees.

If you rename a .12daz to .zip you can unzip it and get the .12da out. That is occasionally useful, though it doesn't help you read the contents.

Extension	What it is
.12da	12d ASCII archive, plain text, the standard handover format
.12daz	The same archive, zipped
.4d	12d configuration files, not project data (linestyles.4d, symbols.4d, drainage.4d, env.4d). Also the original name of the ASCII format before 1999

If you've been sent a .4d config file expecting design data, go back to the sender. That's setup, not geometry.

What's inside a 12d archive

The core unit is the string: a named line carrying coordinates and levels. Strings live in models, 12d's equivalent of layers. A typical design handover contains dozens of models and tens of thousands of strings:

• Control lines and alignments, carrying real horizontal geometry (straights, arcs, transition spirals) and vertical profiles with parabolic curves
• Design strings such as edge of bitumen, kerb, lip, batters and table drains, at true reduced levels
• Survey pick-up from the original field work
• Surfaces (TINs), the triangulated terrain and design surfaces
• Contours, sections, drainage pits and pipes, and often plot sheets and working models nobody needs

That's exactly the information you want when you're checking a driveway grade against the road design, setting a floor level, positioning boreholes along an alignment, or working out how much of a batter lands on your site.

The coordinates are usually real MGA eastings and northings with AHD levels, not drawing coordinates, so extracted geometry lands in the right place on your survey without scaling or shifting. One thing a 12da does not carry is a declaration of which zone or datum those numbers belong to. If you're unsure, ask the sender which MGA zone the job is on before you trust anything you measure.

How to open a .12da or .12daz file

Software	Opens it?	Notes
12d Model	Yes, fully	The native package. Read, edit, design, re-export. A licensed product costing thousands per seat
12d Model via a training licence	Yes, fully, for a while	Authorised training courses bundle a real 12d Model cloud licence, from a free two-month one upwards
12d View	Yes, view only	12d's own free viewer. Plan, section and perspective views, measure, inquire, markup. Windows install. It can't save or export, so nothing comes back out
LayeredGeo 12d to DXF converter	Yes, converts	Free, in the browser. Lists every model, then exports selected data as layered DXF, LandXML, setout CSV or surfaces
Trimble Access / Business Center	Partly	Survey field and office software can extract models from a 12da for setout work
Bentley OpenRail / OpenRoads	Partly	Supports importing 12da and 12daz
Civil 3D with Autodesk's 12d plug-in	Partly	Autodesk publish a 12d Import and Export plug-in (the Data Extension for 12d) for each Civil 3D release. Once installed it imports and exports 12d ASCII files, converting supported objects to native Civil 3D objects. Not every 12d object type comes across, and Autodesk list support for archives up to 12d Model V9
AutoCAD, BricsCAD, MicroStation, Civil 3D without the plug-in	No	No 12da support. Convert to DXF or LandXML first
QGIS, ArcGIS	No	Convert to DXF first, then bring it in
Text editor	Technically	It's plain text, so Notepad++ will show you the raw archive. Unzip a .12daz first, and don't try this on a large file

If you run Civil 3D, check for Autodesk's 12d plug-in first: it brings the supported 12d objects in as native Civil 3D objects and can export back to 12d ASCII. The converter below is for everyone without it, for object types the plug-in doesn't handle, and for anyone working in AutoCAD, BricsCAD or QGIS.

If you only need to look at the design and take a few measurements, download 12d View. It's free, it's official, and it's built for exactly that. If you need the geometry in your own drawing next to your boreholes, footings or survey, a viewer can't help, because it won't write data out. That's the gap the converter fills.

Getting it into AutoCAD or BricsCAD

The 12d Model to DXF converter works in two steps, because a full handover archive usually contains far more than you need.

Inspect. Upload the .12da or .12daz and the tool parses it and lists every model inside, grouped into control lines, design strings, sections, survey, surfaces and so on, with string counts, level ranges, and which control line each design model hangs off. This alone answers the first question you'd ask in 12d: what did they send me?

Select and export. Tick the models you want, typically the control lines and finished design strings, skipping the working models and plot sheets, and download a DXF. A built-in plan preview shows the selected linework before you commit, coloured by model or by elevation.

The DXF keeps the structure of the 12d data rather than flattening it:

• One DXF layer per 12d model (or per string if you prefer), so you can freeze what you don't need, exactly as the designer organised it
• 3D polylines at true coordinates and levels, with no transformation or scaling. If the design is on MGA2020, the DXF lands on MGA2020, and snapping to a vertex reads the actual design RL
• Curves sampled properly. Alignments defined by intersection points are reconstructed through their arcs, spirals and parabolic vertical curves, and arc segments in ordinary strings are densified at the chord interval stored in the file itself
• 12d names preserved. Every entity carries its original string name, model and type as XDATA
• A manifest listing every string exported and anything skipped, so you can confirm nothing important was silently dropped

Open the result in AutoCAD or BricsCAD and it behaves like any drawing: measure offsets from the control line, run a quick surface check against your survey, list a string's levels, overlay your own design.

Beyond DXF: setout reports, LandXML and surfaces

The same upload also gives you:

• Geometry / setout report (CSV), with a free account. An alignment element schedule (every straight and arc with its radius, start and end chainage, length and chord bearing) plus a per-vertex setout listing (chainage, easting, northing, RL) for every string you selected. No more retyping geometry from PDF long sections.
• LandXML alignment export, with a free account. Control lines exported as true alignment geometry with their vertical profiles. Civil 3D, OpenRoads and similar packages import these as native alignment objects, with real arcs and stationing, ready for station-offset reporting, corridor targets or design checks.
• Surfaces (TINs), listed with their point and triangle counts, then written out as 3D triangle faces, contour polylines at your chosen interval, or a LandXML TIN that Civil 3D imports as a native surface. Surfaces come free with every file you convert in the no-sign-up window (below), up to a size cap; very large triangulations need a free account.

What doesn't come across

A DXF is geometry, not a 12d project. 12d attribute data beyond name, model and type, apply-many-function templates and plot frames don't translate to CAD entities. And the usual caveat applies to anything extracted from a handover file: check the linework against the issued drawings before you use it for setout or construction. The converter reports everything it extracts and skips precisely so you can make that check.

Common questions

What is a .12da file? A .12da file is a 12d Model ASCII archive: a plain-text export of civil design and survey data from 12d Model, used across Australia to hand over road design strings, alignments, surfaces and survey pick-up. It is an exchange format rather than the project itself, so it contains only the data the sender chose to export.

What is the difference between .12da and .12daz? They hold the same data. A .12daz is a .12da archive compressed in a ZIP container. Because the format is plain text it compresses heavily, so a 30 MB .12daz can expand to close to a gigabyte of text.

How do I open a .12da or .12daz file without 12d Model? Two free options. 12d View is 12d's own free viewer: it opens the file for viewing, measuring and markup, but it cannot save or export data. The LayeredGeo 12d to DXF converter runs in a browser and extracts the geometry as a layered DXF, LandXML alignments, setout CSV or surfaces so you can use it in AutoCAD, BricsCAD, Civil 3D or QGIS.

Can AutoCAD or Civil 3D open a .12da file? Civil 3D can, with Autodesk's 12d Import and Export plug-in installed: it is a separate download for each Civil 3D release and converts the 12d objects it supports into native Civil 3D objects. Plain AutoCAD, BricsCAD, MicroStation, QGIS and ArcGIS have no 12da support, so for those the archive has to be converted to an exchange format such as DXF or LandXML first.

What coordinate system is a 12d file on? The coordinates in a 12d archive are normally real MGA eastings and northings with AHD levels, but the archive does not declare which zone or datum they belong to. If you are unsure, confirm the MGA zone with whoever sent the file before relying on anything you measure.

Try it

The 12d Model to DXF converter is free. With no sign-up you can inspect up to three files a day at 50 MB each, and download the DXF and surfaces for every file you convert within two hours of your first download that day. A free LayeredGeo account makes conversions unlimited, lifts the upload cap to 2 GB, removes the surface size cap, and unlocks the setout report and LandXML alignment export. Files are processed on upload and deleted within 30 minutes. The one exception is a file that fails to convert, which is kept so we can fix the converter unless you untick that option, and deleted within 60 days at most.

If you're reviewing a design, you probably want the site context to go with it: cadastral boundaries, contours, geology and watercourses clipped to the job, delivered as DXF or Shapefile in your project datum. That's what LayeredGeo GIS Export does, for sites in QLD, NSW, VIC, SA, TAS and the ACT.

About this article. Published by LayeredGeo. It is general information about how property and ground conditions are assessed in Australia, not engineering, planning, legal or financial advice, and it is not specific to any property. Check anything that matters against the source dataset or a suitably qualified professional before you rely on it. If you spot something wrong, tell us at hello@layeredgeo.com.au and we will fix it.

← All articles