I purchased this for my wife so I do not use it however I am a surveyor so I do have vast experience with GPS. GPS signals will not be hindered by thin materials such as cloth. Inside buildings with wood and shingle roofs will throw the location of a bit reducing the accuracy. GPS signals simply do not penetrate metal objects. That being said you should not experience any loss of signal or accuracy using typical clothing items. You may experience some issues if the device was covered with something metallic such as those solar blankets. Perhaps a good experiment to ease your mind is use your cell phone’s GPS tucked into your sleeve as the technology is nearly identical in all small consumer products.