Seven parameters enable the conversion between any two coordinate systems. When a survey needs to produce output based on a local coordinate system, seven-parameter transformation would normally be used to convert geodetic coordinate systems such as WGS 84 or CGCS 2000 to a local coordinate system.

In the 2D map and 3D model functions on DJI Terra, you may select “Seven-Parameter Transformation” or “Calculate Seven Parameters” under “Arbitrary Coordinate System” to generate output based on a local coordinate system. The steps are as follows:

1. Create a data file according to the data import format required by seven-parameter transformation. DJI Terra supports the import of data in TXT or CSV format. The data information and format requirements are as follows:

Coordinate name, latitude (B, degree format), longitude (L, degree format), altitude (H), east (x), north (y), and height (z).

💡[Tip] Data items in a TXT file shall be separated by commas (,) and tabs. Please ensure at least 3 sets of coordinates are used in seven-parameter calculation.

2. Version v5.0.0 has changed the interface UI, and the entrance of the seven-parameter transformation function has been adjusted, and the name has been changed to “transformation”, and the entrance of the function is referenced in the following figure.

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Before version v5.0.0：In “2D Map” or “3D Model”, click “Advanced Settings”, select "Arbitrary Coordinate System", and click "Seven-Parameter Transformation Settings". In the Seven-Parameter Transformation pop-up window, click ">Calculate Seven Parameters" to expand the menu, click "Import", then select the prepared data in Step 1 to import it.

 

3. After importing the data, check whether B/L/H and x/y/z correspond correctly to the order of “Latitude/Longitude/Height” and “East/North/Height”. Note that the x/east coordinate is usually 6 or 8-digit, while the y/north coordinate is normally 7-digit. Headings or other irrelevant information can also be removed using "-" in the “Operation” menu.

 

4. After clicking “Calculate”, you will see the results of the seven-parameter calculation and its residual. Preferably, the residual should be smaller than 0.5 of the expected output accuracy (if the expected accuracy is 5 cm, the recommended residual should be smaller than 0.025 m), so that the transformation result is more accurate. If the residual is too large, you may use "-" to remove the gross error, then click “Calculate” again. After ensuring the residual meets the requirement, click “Apply” to complete the calculation and apply the seven parameters.

 

5. If you will be processing data in the same area in the future, you may click “Export” directly to save the seven parameters in the JSON format. On your next processing, you can then import and reapply the file directly without having to calculate again.