HELI PLT TRESPASSES IN SLEEPING BEAR DUNES NATL LAKESHORE AIRSPACE NEAR TVC. HE IS UNAWARE OF CHART LEGEND REQUESTING THAT PLTS NOT FLY BELOW 2000 FT IN THE CHARTER AREA.

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AFTER RETURNING FROM A PHOTO OP IN THE TRAVERSE CITY MICHIGAN AREA; TVC TWR INFORMED US THAT THEY HAD BEEN INFORMED THAT WE WERE WITHIN RESTR ALT OF THE 'SLEEPING BEAR DUNES NATIONAL LAKESHORE.' I INFORMED THE TWR THE LOWEST AGL WE WERE WAS 400 FT AGL. THE TWR INFORMED US THAT; THAT AREA'S MINIMUM AGL WAS 2000 FT AGL AND HE THOUGHT IT MIGHT BE HIGHER SINCE SEPT/TUE. I INFORMED THE TWR PERSONNEL I WAS SORRY! HOWEVER; ON MY VFR GREEN BAY SECTIONAL CHART FOR THAT AREA; IT SHOWS THE OUTLINED AREA; BUT NO NOTATION AS TO ALTS OR SUA. THE CLOSEST TO ANYTHING I FOUND ON THAT CHART WAS BY 'ISLE ROYALE NATIONAL PARK.' SAME IDENT WAS ABOUT NO ACFT LNDG ON OR WITHIN 4 1/2 MI. TWR PERSONNEL INFORMED ME THAT I WOULD NOT FIND ANYTHING ABOUT THE ALT RESTR ON THE GREEN BAY SECTIONAL; BUT I WOULD FIND IT ON THE MICHIGAN AERO CHART 2004 EDITION. IT'S HARD TO FIND NOT BEING ON THE LEGEND. I FOUND ONE MICHIGAN CHART ANOTHER PLT HAD; AND FOUND A NOTATION ABOUT ALT WHICH READS; 'BOUNDARIES OF NATL WILDLIFE REFUGE AREAS. ACFT SHOULD MAINTAIN 2000 FT AGL OR HIGHER.' IN THE LEGEND IT SIMPLY STATES 'NATL PARK AREA; NOT WILDLIFE REFUGE AREA OR ANY RESTRS.' I TRULY BELIEVE VIOLATIONS OF THIS AIRSPACE CAN BE AVOIDED BY: PLACING THE IDENT OF THE AIRSPACE SYMBOL IN THE LEGEND OF THE 'GREEN BAY SECTIONAL' -- THE FEDERAL GOV STANDARD CHART; NOT JUST A MICHIGAN AERO CHART THAT IS PUT OUT BY THE STATE OF MICHIGAN WITH LIMITED DISTRIBUTION. ALSO A BOX WITHIN THE AREA OF THE SLEEPING BEAR DUNES WITH THE RESTRS ON THAT AIRSPACE; LIKE THEY DID WITH THE ISLE ROYALE AREA. ONE ADDITIONAL THOUGHT IS THE WORDING; IT SHOULD SAY 'SHALL...' NOT 'SHOULD MAINTAIN 2000 FT AGL.'