In addition to hardware performance, GPS accuracy is subject to the environment and requires direct communication between the receiver and the satellite. When objects cover the surrounding sky (surrounding trees, metal bodies, urban buildings, bodies, etc.), reflection and weakening of the signal will occur. At this point, the GPS will exhibit reduced accuracy, such as: incorrectly shift or deviations from the actual path.
Therefore, the placement of the receiver can significantly affect the accuracy.
When carrying a GPS receiver, usually, the antenna is fixed higher, the area facing the sky is larger, the better the reception. Good positions include the top pocket of the backpack, mounted on top of a cycle helmet, or a roof antenna on a car.
The theory of this article is quoted from the Wiki“Accuracy_of_GPS_data”
English: https://wiki.openstreetmap.org/wiki/Accuracy_of_GPS_data
German: https://wiki.openstreetmap.org/wiki/DE:Genauigkeit_von_GPS-Daten

For a high accuracy GPS track, here is the recommended GPS placement.

Recommendation: ★★★★★

Place it under the windshield.

Do not place in car cup holder.

Recommendation: ★★★★

Hand the front of the receiver towards the sky.

Do not hold the front of the receiver in your hand.

Recommendation: ★★★

Place the front of the receiver face up in the backpack.

Do not place the front of the receiver inward.

Recommendation: ★★

Place the front of the receiver face up in the pocket.

Do not point the front of the receiver towards the body.