General aviation pilot reported flying below the minimum altitude for that sector during approach. Pilot climbed to safe altitude and to fly clear of nearby cranes.

Narrative

IFR flight planVectors to a Visual approach to RWY 28I loaded Visual RWY28 in GPS for added guidance.At about 3.5 miles to final I saw cranes for the port. We were going to clear them without a problem but I felt I was lower than I was comfortable with so I was going to level off until getting closer to runway.At that point Tower informed me there was a 1500' minimum for that sector.I initiated a climb.Reviewing where I could have been more prepared:91.119 states 1000' above obstacle in congested area EXCEPT when necessary for takeoff and landing. I was in landing phase; following vectors but I wish I had more awareness of the cranes earlier. At a 3° Glide slope at 3.0 miles I should be at 880 feet. To be at 1500' 3 miles out I would need a steeper glide slope; 5°.I didn't see any Airport NOTAMs for the cranes as an obstacle.I don't see any comments on Foreflight for SAV about this issue. Internet search didn't reveal any information.Cranes are not shown on the IFR Low but are on the VFR Sectional and RNAV RWY 28 approach plate but maybe should be more prominent