COORDINATE SYSTEMS & HEIGHT REFERENCES
Make the survey line up in the reference the project actually needs
A DJI Terra coordinate system defines how the positions in a reconstruction are expressed. If an export appears shifted, rotated or at the wrong elevation, the problem may be its reference or transformation rather than the reconstruction itself.
This guide separates horizontal coordinates from heights, explains EPSG and PRJ files, and gives a practical setup and troubleshooting method for survey deliverables. It complements the accuracy guide with a closer look at reference handling.
Horizontal coordinates and heights are separate decisions
A project can line up correctly in plan and still have incorrect elevation values. Record the horizontal reference, the height reference and their units independently. A label such as “WGS84” alone is rarely enough to describe an engineering handover.
| Item | What it describes | What to record |
|---|---|---|
| Horizontal CRS | The meaning of positions in plan. | Full name, authority code where applicable, datum and projection. |
| Height reference | The surface or datum from which heights are measured. | Ellipsoidal, orthometric or specified local heights and the relevant model or benchmark. |
| Units and axis order | How numeric fields should be read. | Metres or feet, degrees where applicable, and the order of coordinate columns. |
| Transformation | The operation between source and target references. | Selected method, support files, parameters and validation evidence. |
Start with the client’s specification and the reference of your source observations. Do not choose a coordinate system because its name looks familiar or because the preview seems close to a background map.
What is an EPSG code, and what does it not tell you?
An EPSG identifier refers to a defined coordinate reference system or related geodetic object. In Terra, DJI documents searching the coordinate-system database by name or EPSG code. Check the full definition and intended area of use before selecting a result.
For example, a geographic reference expressed in latitude and longitude is different from a projected reference expressed in eastings and northings. UTM also depends on the correct zone and hemisphere. One code does not automatically describe a separate local height reference.
Assigning a label is not transforming coordinates
If a downstream application lets you assign a CRS, that action changes how the existing values are interpreted. It does not necessarily calculate new coordinates. Transforming data requires the appropriate operation between the known source and target references.
If the handover continues into GIS, our DJI Terra to QGIS guide explains layer and project CRS checks. For BIM, see the Terra to Revit point cloud workflow.
Ellipsoidal height, orthometric height and the geoid
GNSS observations and engineering elevations may refer to different height surfaces. An ellipsoidal height refers to a mathematical ellipsoid. An orthometric height refers to a geoid-based height system. A geoid model supplies the relationship needed by an applicable height conversion.
The usual relationship is H = h − N, where H is orthometric height, h is ellipsoidal height and N is geoid height. NOAA’s explanation of ellipsoidal and orthometric height describes the principle. The correct model must match the applicable datum and survey area.
A simple numerical example
Suppose, purely for illustration, h is 125.40 m and the applicable N is +42.10 m. Then H is 83.30 m. These values are not a geoid recommendation, a local benchmark or a Terra processing result.
A map could therefore be well positioned horizontally while its displayed heights differ by many metres from engineering drawings. That can be a reference mismatch, rather than a similarly large reconstruction error. Identify the source and target before applying a correction.
A constant manual offset may also be insufficient across a larger area or between different datums. The height relationship and uncertainty must be assessed for the actual project.
Set the output coordinate system in DJI Terra
DJI’s output coordinate system guidance distinguishes Known Coordinate System from Arbitrary Coordinate System. It also documents horizontal datum selection, geoid settings, PRJ import and seven-parameter transformation routes.
- Write down the source reference of the image positioning, control observations and any imported POS data.
- Agree the target horizontal reference and height system with the recipient. Include units and any local benchmark definition.
- Select the documented Terra output-reference route appropriate to those inputs. Review the full horizontal definition.
- Check the geoid or vertical settings separately. Confirm that the selected model or support file is actually available and applicable.
- Review imported control-point fields and their declared reference. Preserve a copy of the original observations.
- Process a representative area and compare the result with independent known points before delivering the full survey.
Menu labels depend on the installed release. Use the current manual and avoid treating a selection that remains at a default value as evidence that a desired vertical conversion has been performed.
Before changing software versions to access a setting, review our Terra versions and release notes guide.
Keep GCP, POS and output references consistent
A ground control point is a surveyed observation with a coordinate definition. POS records likewise need a known meaning for their position and height fields. If either source is misinterpreted, a reconstruction may still look convincing while its relationship to the project reference is wrong.
- Check point names, column order, decimal format and units before import.
- Confirm whether the height field is ellipsoidal, orthometric or a specified local level.
- Keep the original coordinate file and any transformed version separately.
- Document the transformation used rather than silently overwriting source values.
- Reserve independent check points to evaluate the result in the target reference.
Use our accuracy, GCP, RTK and PPK guide for control strategy. The quality report guide explains how to review residuals without confusing fitted control with independent acceptance evidence.
Avoid a double height conversion
If control heights already use the required engineering reference, do not apply an additional geoid correction by assumption. Trace the height treatment through the import, reconstruction and export stages, then verify it against known checks.
PRJ files, local grids and custom geoid support
A PRJ file describes a coordinate reference; it does not contain newly measured positions. Terra’s documented PRJ import route can define an output reference. It cannot, on its own, establish an unknown relationship between an arbitrary site grid and global coordinates.
For a local engineering grid, obtain the authorized definition and transformation evidence from the responsible survey team. A similar name or an approximate alignment is insufficient. Validate at multiple locations, including the edges and elevation range of the site.
DJI’s July 2026 update announcement describes importing local geoid files using its documented GeoTIFF/GTG workflow. This is specific support for a suitable geoid grid, not permission to substitute an arbitrary DSM or elevation raster.
Check grid coverage, datum compatibility, units and release requirements before use. Preserve the exact grid supplied for the project. If the target reference is unsupported or insufficiently defined, agree an approved conversion outside Terra and validate the final handover.
Troubleshoot shifted maps and incorrect elevations
| Symptom | Check first | Useful next step |
|---|---|---|
| A large horizontal displacement | Source CRS, target CRS, UTM zone, hemisphere and coordinate column order. | Compare a known location using the original reference metadata. |
| Correct plan position, wrong heights | Height datum, geoid treatment, units and control-height definition. | Compare several independent benchmarks. |
| A nearly constant local shift | Local-grid origin and the applied transformation. | Review the authorized transform rather than dragging the model. |
| Offsets that change across the site | Transformation suitability and reconstruction or control quality. | Inspect distributed independent checks and report residual patterns. |
| Unexpected scale or exaggerated elevations | Metres/feet interpretation and downstream import settings. | Verify a known distance and height difference. |
| A downstream application disagrees with Terra | Export metadata and the receiving application’s CRS handling. | Inspect the numeric coordinates and test one representative output. |
Keep troubleshooting systematic: change one documented setting at a time, retain the prior export, and compare the same check observations. Do not repeatedly select CRS codes until a model appears to fit.
For failures during processing rather than reference handling, use our reconstruction troubleshooting guide.
Include a coordinate reference note with every handover
A concise reference note saves the recipient from guessing how to interpret the files. Put it beside the GeoTIFF, LAS or model output, and keep it with later revisions.
- Full horizontal CRS name and identifier, plus applicable datum details.
- Height reference, geoid model or local benchmark definition.
- Coordinate and height units and relevant axis or column order.
- Source references and the transformation used.
- Software version, capture date and output revision.
- Independent check results and any spatial limitations.
- A known test location or benchmark that the recipient can verify.
Test the actual delivered file in the intended application. A correct native project is not sufficient if the export or receiving workflow interprets its reference differently.
DJI Terra coordinate system FAQ
Does a horizontal EPSG code define my engineering heights?
Not necessarily. Record the height reference separately and confirm the applicable vertical datum, geoid model or local benchmark.
Why are Terra elevations different from my survey drawings?
Possible causes include different height references, units, control interpretation or transformations. Compare known benchmarks and trace the settings before changing the reconstructed surface.
Will importing a PRJ file fix an unknown local grid?
A PRJ describes a reference. Establishing the relationship to a local grid still requires a valid definition and transformation evidence.
Can I fix a shifted cloud by moving it manually in CAD?
A manual move may hide the symptom without establishing the correct reference. Use a documented transformation and verify independent positions and heights.
Which Terra license should I choose for coordinate settings?
DJI’s support guidance identifies coordinate-setting support in Standard and Flagship. Confirm the sensor, reconstruction task and required transformation workflow in our license guide before selecting the product.
Check the reference requirements before choosing your workflow
Send us your acquisition system, required outputs and target software. We can help identify the Terra licensing and processing requirements; project coordinate definitions should come from the responsible survey team.
Official documentation
- DJI output coordinate system settings
- DJI Terra coordinate and control-point FAQ
- DJI July 2026 update: local geoid import support
- NOAA explanation of the ellipsoid/geoid height relationship
Independent guide by Drone Emotions. Documentation reviewed on 9 October 2026. Consult the documentation for the installed software and capture-system releases.
