4.6 Coordinate Systems and Datums
The coordinate system configuration in LixelStudio decides whether the output point cloud lands in the right place in the world. Operators without a surveying background often find this the most confusing part of georeferencing. This page covers what you actually need to configure it correctly.
Core Concepts
You do not need a surveying background to configure coordinate systems in LixelStudio, but you do need to understand four terms.
Ellipsoid
A mathematical model of the Earth's shape used as the reference surface for coordinates. Different systems use different ellipsoids. WGS84 is the global GPS standard. GRS80 underlies most modern national systems. The RTK receiver records in whatever ellipsoid your CORS network transmits, so you need to know which one.
Datum
A specific realization of a coordinate system, defined by an ellipsoid plus a set of control points that tie it to the actual Earth. WGS84, NAD83, and ETRS89 are datums. Two systems can share an ellipsoid yet be different datums because they are anchored differently. WGS84 and GRS80 are nearly identical, but WGS84 and NAD83 are not; positions in the same area can differ by over a meter depending on which you use.
Projection
A transformation that converts curved geographic coordinates (latitude and longitude) into flat planar coordinates (Easting and Northing). Every projection introduces some distortion. UTM is the most common global system. State Plane, local grids, and national systems each have their own definitions. LixelStudio outputs projected coordinates, so you must specify the target projection.
Helmert Transformation (Seven Parameters)
When the source datum of your RTK corrections differs from the target datum of your output, a transformation converts between them. The Helmert transformation uses seven parameters: three translations, three rotations, and a scale factor. They are specific to each datum pair and region and must come from an authoritative geodetic source, not from estimation.
What the RTK Receiver Records
The RTK receiver records latitude and longitude: geographic coordinates in the ellipsoid of your CORS network. It does not record Northing and Easting. That means the projection step happens in LixelStudio during processing, not in the field. Your field job is to confirm which ellipsoid the CORS network transmits. Everything else is configured in software.
This is the same for the L2 Pro external RTK module (Standard or Survey grade) and the K2 built-in UM980 module. Both record geographic coordinates in the active CORS ellipsoid.
If your NTRIP provider is not in the LixelGO dropdown, select Custom and set the ellipsoid to match your CORS network. If the ellipsoid is also missing, select Custom and enter the semi-major axis (a) and inverse flattening (1/f) manually. These are published by the geodetic authority for your system.
Supported Projection Types
LixelStudio supports four projection types. Most projects outside Mainland China use UTM or Transverse Mercator.
- Gauss Kruger (3-degree zones)
- Gauss Kruger (6-degree zones)
- UTM
- Transverse Mercator
State Plane coordinates in the US. There is no native State Plane dropdown, but most zones can be configured manually. Zones that use Transverse Mercator (the majority) work by selecting Transverse Mercator and entering the zone's central meridian, false easting, false northing, and scale factor from the EPSG database. Zones that use Lambert Conformal Conic are not currently supported by the projection engine. US Survey Feet output is also not native and requires a post-processing conversion from metric.
Look up the EPSG code for your target system at epsg.io. The record provides every projection parameter you need: central meridian, false easting, false northing, latitude of origin, scale factor, and the associated ellipsoid.
Scenario 1: Same Source and Target Ellipsoid
The simpler case. Your CORS network transmits in WGS84, and your output is also WGS84-based (such as UTM WGS84). No datum transformation is required, only projection.
In LixelGO, set the RTK type and ellipsoid to match your CORS network. In LixelStudio, set the source coordinate and ellipsoid to match LixelGO, set the target coordinate and ellipsoid to your output system, and enter the projection parameters from the EPSG record. No seven parameters are needed.
Scenario 2: Different Source and Target Ellipsoids
This case needs Helmert parameters in addition to the projection. It occurs when your CORS network transmits in one datum (for example WGS84) but the output uses a different ellipsoid (for example JGD2011 for Japan, or KGD2002 for Korea).
In LixelStudio, after setting the source and target systems and ellipsoids, you will be prompted for the seven Helmert parameters. These come from the official geodetic authority for your region. They cannot be derived from EPSG records alone; you need the published parameters for the specific datum pair.
Example: WGS84 to JGD2011 (Japan)
Set RTK type to Custom, ellipsoid to WGS84 in LixelGO. In LixelStudio, set source to WGS84, target to JGD2011 (target ellipsoid GRS80, fixed for JGD2011). Enter Japan Plane Rectangular projection parameters from EPSG (for example EPSG:6677 for CS IX). Import the seven-parameter file for the WGS84 to JGD2011 transformation.
Example: Custom Ellipsoid (GRS67)
If your CORS network transmits in GRS67 (used in parts of South America), it will not appear in the dropdown. Set type to Custom, ellipsoid to None, then enter your host and mountpoint. In LixelStudio, set source and target ellipsoid to Other and enter the GRS67 parameters: semi-major axis 6,378,160 m, inverse flattening 298.25.
Finding Your Parameters
- Projection parameters: the EPSG record for your target system at epsg.io lists everything LixelStudio needs
- Ellipsoid parameters (semi-major axis and inverse flattening): from the geodetic authority for the system, or EPSG records for standard ellipsoids
- Seven Helmert parameters: from the national geodetic authority for the target datum. Do not use unofficial sources; small errors here produce systematic offsets across the whole dataset
- If unsure of your CORS network's datum: ask your NTRIP provider which ellipsoid and datum they transmit. This is standard information they will have
- For most projects outside Mainland China: WGS84 source, UTM target, same-ellipsoid case (Scenario 1). Look up your UTM zone in the EPSG index and enter the parameters directly
Coordinate configuration understood. Final page in Module 4: 4.7 The Hybrid Approach, which combines RTK and GCPs for the highest accuracy on the platform.
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