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.
IN THIS ARTICLE
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 easting or longitude | global northing or latitude | global elevation | calibration type (optional)* |
| 1 | |||||||
| 2 | |||||||
| 3 | |||||||
| 4 |
The table must be in CSV format with the required fields:
-id (optional)
Must be ASCII characters.
-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.
Name of custom WKT file
Provide the name of the desired site calibration file. The name of the WKT file will appear in the quality reports from PIX4Dmatic and PIX4Dcloud. If no name is provided, Pix4D will assign an appropriate name. The name must be ASCII characters.
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