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I am new to QGIS.

My project involves county-level data. The problem is that US counties keep changing! (See the US Historical Counties project: http://publications.newberry.org/ahcbp/)

Since my other data do not keep account of these changes, I plan to merge counties to create a single consistent geographic unit over time.

For example, if county A splits into county A and county B, then I simply treat county B as county A for the remainder of the time sample.

Are there any good ways to do this in QGIS, without arduously going through the attribute table?

closed as unclear what you're asking by underdark Apr 26 '14 at 22:49

Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

  • In which format do you have the data about counties splitting/merging over time? – underdark Sep 23 '13 at 20:39
  • Ok but how is the temporal aspect modeled? – underdark Sep 23 '13 at 20:53
  • From the help file, "The Historical Counties master shapefile contains separate polygons for each unique county shape during the state's history. Due to the numerous changes that have occurred in county boundaries, the master shapefile includes many overlapping polygons. Each polygon includes field values specifying the start and end dates for that particular shape." – Cornelius Sep 23 '13 at 20:56
  • For an exemplary way to handle this problem, which occurs at all levels of administrative organization, study the US Census Bureau's relationship files. A good place to start in the documentation might be with one of the "Understanding ..." documents. – whuber Sep 23 '13 at 21:17
  • For me, the problem description is still too vague. Maybe you could add one specific example of what you need to solve. – underdark Sep 23 '13 at 21:18

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