This guide describes how camera position is calculated from the center point, zoom, and camera rotation.
The Transform variables center, elevation, zoom, pitch, bearing, and fov control the location of the camera indirectly.
elevation sets the height of the "center point" above sea level. In the typical use case (centerClampedToGround = true), the library modifies elevation in an attempt to keep the center point always on the terrain (or 0 MSL if no terrain is enabled). When centerClampedToGround = false, the user provides the elevation of the center point.
zoom sets the distance from the center point to the camera (in conjunction with fovInRadians, which is currently hardcoded).
Together, zoom, elevation, and pitch set the altitude of the camera:
See MercatorTransform::getCameraAltitude():
getCameraAltitude(): number {
const altitude = Math.cos(this.pitchInRadians) * this._cameraToCenterDistance / this._helper._pixelPerMeter;
return altitude + this.elevation;
}
To allow pitch > 90, the "center point" must be placed off of the ground. This will allow the camera to stay above the ground when it pitches above 90. This requires setting centerClampedToGround = false.
The same math applies whether the center point is on terrain or not, and whether the camera is above or below the ground:
To help users position the camera, Camera exports the function calculateCameraOptionsFromCameraLngLatAltRotation().