Online Help > Maps & Layers > How to calibrate an image to use it as a map?

How to calibrate an image to use it as a map?


The application allows you to use regular images as maps. In order to correctly locate items on this map (points, tracks, etc.), the application must know what is the exact area covered, this is done by the calibration process: after displaying the image, you must match 4 points with another existing and correct map. This process is done only one time, then the image is imported as a regular map file.

This feature requires an in-app purchase.

The calibration process used by this application requires 4 points, which is enough to correctly match an image over a base map without knowing the exact map projection which is used, and gives satisfactory result for maps with limited areas.

The supported image formats are: JPEG, PNG, BMP1, GIF1, WebP1,2, HEIF1,3.
1: size limit may apply based on your device configuration; 2: Android 4.0+; 3: Android 8.0+

To calibrate an image:

file-based-calibrate-1.jpg

When you've selected the correct folder, tap the image to start the import process. When the image has been imported, it's displayed over the current map.

By default, the 4 calibration points are placed on the four corners.

file-based-calibrate-2.jpg

For each calibration point:

Repeat those steps for the three other calibration points.

Be careful to choose a map feature that is stable across the two maps and small enough: a railroad crossing, a church, an historical building, etc. Note that some features like riverbeds are not stable: they can move with time.

file-based-calibrate-3.jpg

In case you make a change by inadvertence, you can use the Undo icon to cancel the last action.

When the four calibration points are correctly placed, tap the Close icon to terminate the calibration process.