A reference for engineers, BIM coordinators and CAD technicians receiving drone data on Irish projects.
You’ve been handed a package of drone-survey deliverables and you’re wondering where to start. This guide is the answer. It covers every file type you’ll receive from a survey-grade drone operator in Ireland, what software reads each one, how to import them into AutoCAD Civil 3D and Revit, and what the coordinate system numbers at the top of each file actually mean.
Written for junior engineers, BIM coordinators and CAD technicians in Irish consultancies. Keep a copy on your desktop – the typical 10-minute “what is this file?” question is answered in the glossary on the last pages.
Engineers or BIM coordinators working on Irish infrastructure, earthworks, quarry, renewables, or heritage projects where a drone survey has been commissioned – whether by Drone Services Ireland or another provider.
A standard earthworks/topographic drone survey delivery from a survey-grade operator contains the following files. Depending on your scope, some may be optional. Every file should reference the same coordinate system (ITM / Malin Head) – see page 08.
.LAS / .LAZ
The raw 3D measurement of every surface the drone saw. Every point has X/Y/Z + RGB colour + classification code. The master dataset that everything else is derived from.
.XML (LandXML) · .TIF (float32)
Bare-earth (DTM) and first-surface (DSM) grids, ready for earthworks volume calculations and cross-sections. LandXML goes straight into Civil 3D as a surface.
.TIF (GeoTIFF)
A flat aerial photograph of the site, georeferenced. Use as a drawing backdrop, for tender packs, or for visual reference in BIM models. Default GSD (ground sample distance) is 2 cm on most sites.
.DWG / .DXF
CAD-native contour plans at your specified interval (0.25 m is typical for earthworks) and cross-sections at the chainages you request. Opens straight into AutoCAD without translation.
The quality record. Names the GCPs, reports the RMSE against each check point, confirms the coordinate system, states the flight conditions. Goes into the project file for the consulting engineer sign-off.
The point cloud is the foundation of every other deliverable on the previous page. It’s a list – often tens or hundreds of millions of entries long – of 3D points the drone measured. Every point carries coordinates, colour, intensity (for LiDAR), and a classification code.
LAS is the uncompressed ASPRS standard format for point-cloud storage. Readable by every GIS/CAD package.
LAZ is the same data, losslessly compressed – typically to 10–15% of the LAS size. Modern software reads LAZ directly; older versions need a free converter (laszip).
We deliver LAZ by default. Ask for LAS if your software chokes on compression.
0 Never classified1 Unclassified2 Ground (the bare-earth points)5 High vegetation6 Building7 Noise / outlier9 WaterA properly classified cloud lets you extract a bare-earth DTM just by filtering to class 2.
Your consulting engineer wants the ground-classified cloud. Your BIM coordinator sometimes wants the full cloud (buildings + vegetation retained) for context model extraction. Ask before clipping.
A “surface” in engineering terms is a continuous 3D mesh or grid that represents the top of terrain or features. Drone survey operators deliver these in a few common formats so you can take them straight into your design software.
The bare earth. Vegetation, buildings, vehicles have been stripped. This is what civil engineers design against for earthworks, drainage, and grading.
The first surface the drone saw. Includes treetops, roofs, everything. Useful for line-of-sight analysis, visibility studies, solar irradiance modelling, and contextual BIM.
.XML (LandXML 1.2)
The right format for AutoCAD Civil 3D. Import as a surface in one click: Insert > Surfaces > Create from LandXML. The mesh triangulation is already done – no need to re-grid.
.TIF (GeoTIFF float32)
A regular grid of elevation values. Each pixel is a height in metres. The right format for GIS work – QGIS, ArcGIS, Global Mapper all read it natively. Specify the cell size you need (0.25 m is common for earthworks-scale sites).
.xyz (ASCII)
A text file, one row per point: X Y Z. Universal but slow to read on large sites. Handy when your software doesn’t accept anything else, or for scripting.
An orthomosaic is built by stitching hundreds of overlapping drone photographs into a single flat image, then correcting each pixel for camera angle and terrain so it sits flat like a map rather than curved like a photograph. The result is an aerial view where you can measure distances and areas directly off the image.
GSD is the real-world size of one pixel. On a typical earthworks site, we fly to hit 2 cm GSD – one pixel covers 2×2 cm on the ground. So a 30 m×30 m building spans ~1,500 pixels.
Higher GSD (smaller pixels) = more detail but bigger files + longer flight. 2 cm is the sweet spot for engineering-grade work. For tender-pack aerial photos, 5 cm is usually enough.
You should be able to open the orthomosaic in QGIS and see it drop onto the correct location on the OS Ireland basemap with no manual referencing. If you can’t – the CRS is wrong, see page 08.
MAPIINSERT or Civil 3D Insert > ImageIf the end user is GIS, deliver GeoTIFF. If the end user is CAD, deliver both GeoTIFF (for reference) and a JPEG tile with world file (lighter, faster to attach). A big uncompressed GeoTIFF can be 1.5 GB – CAD users appreciate a 40 MB JPEG alternative.
CAD-native vector deliverables are the straight-into-the-drawing outputs. Unlike raster (orthomosaic) or grid (DTM GeoTIFF) data, these arrive as clean AutoCAD entities – polylines, points, text – already on sensible layers and ready to reference from your design drawings.
DWG is AutoCAD’s native format. Faster, smaller, preserves more metadata. Use this unless a specific tool in your chain can’t read it.
DXF is the ASCII interchange format. Lossy compared to DWG but readable by almost every CAD tool: Bricscad, MicroStation, Rhino, Inkscape, QGIS.
CONTOUR-MAJOR, typically 1 m intervalCONTOUR-MINOR, typically 0.25 m intervalCONTOUR-TEXTOpen the DWG in AutoCAD and check two things: (1) the insertion point is (0,0,0) in ITM coordinates, meaning the drawing sits in true-world position; (2) the UNITS command confirms metres. Both are standard but worth verifying before you xref into your master drawing.
Delivered as a separate DWG per request. Each cross-section shows chainage, ground level profile at selected points, and the station markers. Typical deliverables use the same drawing template as Civil 3D’s default section sheet so you can drop them straight into your tender drawings with minimal re-styling.
Every file in your deliverable package needs to be in the same coordinate system or your team will spend a week re-projecting data instead of designing with it. Here’s what an Irish engineering project actually needs.
ITM (EPSG:2157) is the standard horizontal projection for Ireland since 2001. It replaced the older Irish Grid (TM75, EPSG:29902) which you may still encounter on legacy OS maps.
Easting values around 700,000 m, northing values around 730,000 m for Dublin. If your file has easting values near 6 digits starting with 3 and northings starting with 2, it’s probably in Irish Grid, not ITM – a 150 m offset.
Heights reference Malin Head, County Donegal – the zero point of Irish height measurement. GNSS equipment measures ellipsoidal height (distance from the centre of the Earth); what you want is orthometric height (height above Malin sea level).
The conversion uses a geoid model. In Ireland, the current one is OSGM15. A survey-grade operator applies OSGM15 during processing so your LandXML and CAD heights are already in Malin Head metres. If the residuals report doesn’t mention OSGM15, ask – uncorrected ellipsoidal heights are roughly 55 m off true Malin heights and will destroy your earthworks volumes.
PROJCS["IRENET95_Irish_Transverse_Mercator".EPSG:2157.<CoordinateSystem> – name should be IRENET95 / Irish Transverse Mercator.MAPCSASSIGN command – should confirm IRENET95-IrishTM (or similar spelling depending on release).Calling OSGM15 “the datum”. Malin Head is the datum. OSGM15 is the geoid model used to convert GNSS measurements to Malin Head metres. Both need to be right; one is the reference, the other is the conversion method.
The main cost of drone-survey data to a consulting office is transfer time and storage. Here’s what to plan for. Numbers are indicative – actual sizes depend on GSD, point density, classification depth, and compression level.
| Deliverable | 10 ha site | 50 ha site | 100 ha site |
|---|---|---|---|
| Point cloud (LAZ) photogrammetry, 500 pts/m² | 220 MB | 1.0 GB | 2.2 GB |
| Point cloud (LAZ) LiDAR, 300 pts/m² | 180 MB | 850 MB | 1.7 GB |
| Orthomosaic (GeoTIFF) 2 cm GSD | 180 MB | 900 MB | 1.5 GB |
| DTM (GeoTIFF float32) 0.25 m grid | 30 MB | 150 MB | 350 MB |
| LandXML surface triangulated, thinned | 12 MB | 50 MB | 110 MB |
| Contour DWG 0.25 m minor, 1 m major | 8 MB | 35 MB | 80 MB |
| PDF report | 2 MB | 3 MB | 4 MB |
| TOTAL zipped delivery | ~600 MB | ~2.8 GB | ~6 GB |
Keep the original LAZ and the residuals PDF forever. Everything else can be re-derived. If disk space is tight later, those two files are the minimum you need to reconstruct the project data if the derivative files get corrupted or overwritten.
Step-by-step for a clean first import into a new Civil 3D drawing. Assumes Civil 3D 2022 or later; ribbon paths may differ in older releases.
_AutoCAD Civil 3D (Metric)_ template. Set your units and coordinate system first: MAPCSASSIGN → IRENET95.IrishTM (EPSG:2157).Insert > Point Cloud > Attach. Browse to the .LAS or .LAZ file. Civil 3D reads LAS natively; for LAZ, the 2023+ versions support it directly, earlier versions need a conversion first.IRENET95.IrishTM. If the file already has a .prj sidecar, Civil 3D will auto-detect.0,0,0, scale 1, rotation 0. Do NOT tick “Specify on-screen”. You want the cloud to land in true-world position.ZE (Zoom Extents). You should see the point cloud covering the site in ITM coordinates.Site01_Drone.lazIRENET95.IrishTM0, 0, 01.00°Point Cloud > Create Cropped > By Classification. Choose class 2 (ground) only.Surfaces > Create Surface > From Point Cloud. Name it EXISTING_GROUND, choose a style with 1 m major / 0.25 m minor contours.Surfaces > Utilities > Surface Properties. Check the statistics – min/max elevation should match the values on the residuals report.If we’ve delivered a LandXML file alongside the LAS, skip the cloud-to-surface step entirely. Insert > Import > LandXML and you get a ready-to-use Civil 3D surface in seconds. This is always faster and cleaner than deriving the surface yourself unless you need to filter or clip first.
Revit doesn’t natively read GeoTIFF rasters as georeferenced layers. The workflow is to set up shared coordinates from the drone data first, then attach the orthomosaic as an image reference. Here’s the production pattern.
Insert > Link CAD. Crucially: set Positioning to Auto – By Shared Coordinates. If Revit asks whether to inherit the coordinates, click Yes.Manage > Coordinates > Acquire Coordinates. Pick the linked DWG. Revit now knows your project is in ITM.Manage > Coordinates > Specify Coordinates at Point. Pick a known GCP location on the linked DWG. The coordinates should match the GCP table in the drone residuals report..jgw), preserving the CRS.Insert > Image, browse to the JPEG. Revit doesn’t read the world file automatically, so you’ll need to manually position.Revit images default to 1 pixel = 1 Revit-unit. A 2 cm GSD orthomosaic has 50 pixels per metre. You’ll need to scale by 0.02 (or input via the image scale property) to get real-world scaling. Test by measuring a known feature – a 10 m building should measure 10 m after scaling.
If your Revit workflow is document-focused (not model-focused), skip the image import entirely. Request a PDF export of the orthomosaic at 1:500 or 1:1000 scale and attach it as a sheet background via Insert > PDF. Loses the georeferencing but is simpler and prints cleanly.
The working vocabulary of drone-survey deliverables. If you can explain these to a colleague, you can read every delivery note from every operator in Ireland.
CORSnet Network
Ordnance Survey Ireland’s national network of 35 permanent GNSS reference stations. Broadcasts RTK corrections nationwide, giving sub-centimetre positioning to any equipped drone or survey instrument within ~35 km.
DTM Surface
Digital Terrain Model. A bare-earth representation of the ground with vegetation, buildings, and other non-terrain features removed. The primary surface for earthworks and grading design.
DSM Surface
Digital Surface Model. The first surface seen from above – top of trees, rooftops, and everything else. Used for line-of-sight, solar, visibility, and contextual BIM.
EPSG Code
A short numeric identifier for a coordinate reference system maintained by the European Petroleum Survey Group. EPSG:2157 is Irish Transverse Mercator; EPSG:4326 is WGS84 longitude/latitude.
GCP Control
Ground Control Point. A painted cross or surveyed marker on the ground whose coordinates are measured independently. Used to tie the drone data to an absolute coordinate system and to verify accuracy.
GeoTIFF Raster
A TIFF image file with embedded geographic metadata. Used for orthomosaics, DTMs, DSMs. Opens georeferenced in QGIS, ArcGIS, Civil 3D, and Global Mapper without a separate world file.
GSD Resolution
Ground Sample Distance. The size of one pixel in real-world units on a drone-captured image. 2 cm GSD means one pixel = 2×2 cm on the ground.
OSGM15 Geoid
Ordnance Survey Geoid Model (2015 release), produced jointly by OSi, OSNI and OS GB. Converts GNSS ellipsoidal heights to orthometric heights referenced to Malin Head datum in Ireland. Replaced the older OSGM15 model. Always applied during survey-grade processing.
ITM Projection
Irish Transverse Mercator. The standard horizontal projection for Ireland (EPSG:2157). Easting and northing values in metres, origin roughly west of the country.
LandXML Format
An open XML file format for exchanging surface and alignment data between design software. Imports cleanly into AutoCAD Civil 3D as a ready-made surface. Extension: .xml.
LAS / LAZ Format
The standard file formats for 3D point-cloud storage. LAS is uncompressed, LAZ is losslessly compressed to ~10–15% of LAS size. Both carry X/Y/Z, colour, classification, intensity.
LiDAR Sensor
Light Detection and Ranging. An active sensor that pulses a laser and measures return time to build a point cloud. Works in low light; multi-return systems penetrate light vegetation.
Malin Head Datum
The reference point for all Irish height measurement, established at the tide gauge in Malin Head, County Donegal. All “metres above sea level” values in Irish drawings reference this point.
Orthomosaic Raster
A flat aerial image, stitched from many overlapping drone photos and corrected for terrain so that every pixel sits in its true-world position. Measurements taken directly from the image are accurate.
Point cloud 3D data
A dense set of 3D points describing every surface a survey sensor measured. The foundational data product from photogrammetry and LiDAR.
PPK Positioning
Post-Processed Kinematic. Raw GNSS observations are logged during flight and matched against reference-station data after the fact. More forgiving than RTK, works offline.
Radiometric Thermal
A thermal image that stores the absolute temperature value at every pixel (not just relative heat). Needed for compliance work: solar PV inspections, insurance claims, building regs.
Residuals Accuracy
The differences between the drone-measured position of a check point and its independently surveyed position. Reported in the survey certificate as RMSE in the horizontal and vertical.
RMSE Accuracy
Root Mean Square Error. The headline accuracy figure for a drone survey. Quoted separately for horizontal and vertical. Sub-5cm RMSE is the survey-grade benchmark.
RTK Positioning
Real-Time Kinematic. The drone receives live correction signals from a reference station (in Ireland, OSi CORSnet) and achieves centimetre-level positioning during flight.
This guide covers the standard deliverables produced by Drone Services Ireland and is published openly as a reference for the Irish engineering and construction community. Copy it, share it, print it, keep it on your server. If it’s useful to one of your colleagues, pass it on.
If you’ve received a survey delivery – from us or another operator – and something is unclear, we’ll walk you through it on the phone. No obligation, no upsell.
087 205 2331
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