an elective flight and another lesson learned re chart scales

so far, i have learned something every time i have flown, and more when solo. today i had the day off and the weather was good so i decided to do a little flying and practice some maneuvers. i was going to go jyo (leesburg)-okv (winchester)-maneuver practice near berryville-jyo. unfortunately, the guy before me got back 35 minutes late which ate into my time. i decided to use my terminal area chart for a change so that i could see more landmarks for practice. the okv landing was ok and i did a quick taxi back and departure. while doing my (shortened) maneuvers i ended up closer to mrb (martinsburg) than i had intended. i didn't enter mrb class-d space but if i hadn't seen the tower in the distance i would have been above their airspace. after getting home i realized why, i usually use a sectional chart which is a different scale than the terminal area chart (i knew that but this is the first time that apparent relative distances sunk in). i'll be more careful next time and i'll use the gps map to be certain of where i am.