There is a German Wikipedia entry for it, but I found no entry for this specific 'Schwedenschanze'.
It is a military Sconce (fortification) (German: Schanze) or Hill fort, the name is based on the Thirty Years' War. Sweden (German: Schweden) was a participant during the war.
It is not necessary, that the Schwedenschanze you found is a real Swedish sconce. It may be a any sconce and the name is only vernacular.
I try to identify your specific Schwedenschanze.
There is a Schwedenschanze on Googlemaps,robably this one: http://alleburgen.de/dispF.php?i=96&t=nb&id=299:
erhalten: Wall- und Grabenreste
Still conserved: Rest of wall and fosse.
early history wall construction
But looking at the map, I have the impression your 'Schwedenschanze' is located at the Stausee Altheim (artificial lake).
There is another website, saying the 'Schwedenschanze' in Ergolding is disappeared.
I found a book Repertorium des topographischen Atlasblattes
Swedish camp during the 30 year war
Schwedenschanze seems to be form the war of Charlemagne against the Huns, perhaps from the Bavarian wars of succession for Duke Georgs of Bavaria-Landshut (death in 1503). This fortification is located in Moesern, has strong and high walls.
Probably a refuge of the inhabitants of the town.
have been cast by the Austrians on 15 April and by the French after the retreat of the former, on 21 April 1809