总之：**this.geolocation.getCurrentPosition（）用于检索设备的当前位置一次，而this.geolocation.watchPosition（）**注册一个处理函数，每次设备的位置更改时都会自动调用该函数，返回更新后的位置。
参考：https://developer.mozilla.org/en-US/docs/Web/API/Geolocation_API
代码示例：

//define the userPositionWatch
userPositionWatch: any;
//Subscriber to the userPositionWatch
this.userPositionWatch = this.geolocation.watchPosition()
    .subscribe(
        (position: any) => {
            // This method will be triggered each time the position of the device changes
            console.debug("geolocation.watchPosition => the callback function have been triggered");
            let data: any = position;
            if (data.coords !== undefined) {
                this.doSomethingWithThePos(data.coords.latitude, data.coords.longitude);
            } else {
                console.error("geolocation.watchPosition() => the callback function have been triggered and the position is undefined", data);
            }
        }
        , (error: any) => {
            console.error("geolocation.watchPosition() => the callback function have been triggered and the there is an error:", error);
        });
//To remove the subscription 
this.userPositionWatch.unsubscribe();
//Another way to remove the subscription
navigator.geolocation.clearWatch(this.userPositionWatch);

this.geolocation.getCurrentPosition()
    .then((position: any) => {
        let data: any = position;
        if (data.coords !== undefined) {
            this.doSomethingWithThePos(data.coords.latitude, data.coords.longitude);
        } else {
            console.error("geolocation.getCurrentPosition() => the position is undefined", data);
        }
    }).catch(error => {
        console.error("geolocation.getCurrentPosition() => the position has error:", error);
    })

我希望你说得很清楚...