从图库iOS 13中选择图像时缺少GPSTimeStamp和GPSDateStamp

Question

当从iPhone版本13.1.2的图库中选择图像时，我看到元数据GPS位置缺少GPSTimeStamp，GPSDateStamp。 我该怎么解释？谢谢！

 ALAssetRepresentation* representation = [info 
 defaultRepresentation];
 NSDictionary *metadata = representation.metadata;
 LogInfo(@"****metadata = %@ *****",metadata)
 =>This is log result :
 "{GPS}" =     {
    Altitude = "6.885073656845754";
    AltitudeRef = 0;
    DestBearing = "20.69101142995269";
    DestBearingRef = T;
    HPositioningError = 10;
    ImgDirection = "20.69101142995269";
    ImgDirectionRef = T;
    Latitude = "10.32532833333333";
    LatitudeRef = N;
    Longitude = "106.4042966666667";
    LongitudeRef = E;
    Speed = 0;
    SpeedRef = K;
};