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Historical Topographic Maps FAQs - 13 Found

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It appears there are multiple copies of the same map as they all have the same date. Is there a difference?

Yes, these are different maps, though the differences are often relatively minor. For a particular cell and scale, most maps have only one original base compilation, but most have later revisions and reprints. Revision methods and extent varied, but most were relatively minor compared to the effort of the original compilation. The date used to identify a map is the larger date in the lower-right corner. If there are multiple editions with the same "Date on Map," it is suggested you look at the other date(s) available. A short definition of each is provided below:

  • Date on Map -- The year of base compilation, or the year of a significant revision.
  • Imprint Year -- The year the map was printed
  • Photo Inspection Year -- The year when a photo inspection was last done on the map
  • Photo Revision Year -- The year when photos were used to revise a map
  • Field Check Year -- The year map content was verified in the field
  • Survey Year -- The year when a field survey was completed for the mapped area
  • Edit Year -- The year the map was last globally edited or revised

Sometimes there are visual differences between two maps that cannot be captured or determined by different dates. Examples are special editions printed with or without woodland (green) tints. The HTMC project scanned all editions with any visual differences in metadata or map content in order to be comprehensive.

Tags: Maps, Topographic, Recreation, Quadrangle, GeoPDF, Scale