Site localization converts global GNSS coordinates into a local coordinate system using a WKT file. To obtain this file, follow the steps outlined in this article.
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Contact Pix4D Technical Support to Request a Custom WKT file
Site Localization, also known as site calibration, is the process of georeferencing a local or arbitrary coordinate system. It involves transforming global coordinates obtained from a GNSS receiver into a project-specific reference frame.
PIX4Dmatic and PIX4Dcloud support custom site localization files formatted in Well-Known Text (WKT), a standardized, text-based representation that includes translation, rotation, and scaling parameters.
Using a site calibration file is especially beneficial when processing high-accuracy drone imagery without ground control points (GCPs). A properly configured WKT file converts GNSS-tagged image coordinates from a global system to align accurately with the local project coordinate system.
Contact Pix4D Technical Support to Request a Custom WKT file
Important: PIX4Dmatic and PIX4Dcloud support the use of site calibration files in WKT (Well-Known Text) format; however, they do not include functionality for creating these files directly within the applications.
To obtain a WKT site calibration file, contact Pix4D Technical Support. Be sure to include the required data outlined below.
To generate a site calibration, provide corresponding local and global coordinates for several reference points. Submit the data in a CSV table with the following columns:
| id (optional)* | local easting | local northing | local elevation | global eating or longitude | global nothing or latitude | global elevation | calibration type (optional)* |
| 1 | |||||||
| 2 | |||||||
| 3 | |||||||
| 4 |
The table must be in CSV format with the required fields:
-id (optional)
-Local easting
-Local northing
-Local elevation
-Global easting or longitude
-Global northing or latitude
-Global elevation
-Calibration type (optional). Value is 0-3.
Calibration type defines how the point is used. This field is optional.
3: 3D calibration
2: 2D calibration only
1: Vertical calibration only
0: Point not used
*If included, the optional "id" and "calibration type" fields must be specified for all rows.
Coordinate System Requirements
Local coordinates: Must be cartesian
Global coordinates: These may be geographic* (latitude/longitude) or projected coordinates, but they must use a known coordinate reference system (CRS) identified by its EPSG code or a composition of a well-known horizontal and vertical CRS.
Examples:
- EPSG: 6318 - NAD83(2011)
- EPSG:6318 (horizontal) + EPSG:5703 (vertical) – NAD83(2011) + NAVD88
*If the global coordinate system is geographic (latitude-longitude), PIX4Dmatic automatically applies a suitable projected coordinate system for processing. If the global system is already projected, that projection is retained.
Minimum Point Requirements
3D or 2D calibration: A minimum of three points, however four or more are recommended for greater accuracy.
Vertical-only calibration: At least one point if global coordinates are projected. Otherwise, three points are required.
Other Pix4D options for creating WKT files
PIX4Dcatch: Site calibration files can be generated using PIX4Dcatch with a supported GNSS device. For more information: Site Localization - PIX4Dcatch RTK
PIX4Dmapper: PIX4Dmapper can export site calibration files compatible with PIX4Dmatic. For more information: How to compute a Site Calibration file - PIX4Dmapper