[Qgis-user] Building Historical Maps

[kirk]

Hi JamesIt may be more efficient to digitize directly from scanned and georeferenced historical maps to segment the current data. For example lakeshore can be copied over from the current digital data do you do not have to digitize Georgian Bay and its many islands.  As you go back in time, maps tend to be less accurate so you may run into problems.  If you use township lines of baselines (ie. the Niven Line in Northeastern Ontario) as you key features to georeference your historical maps Yolo, you might have  better luck getting everything to fit on the modern database.  Georeferncing is a straight forward procedure.  Kirk SchmidtSent from my Galaxy
-------- Original message --------From: James Cobban <webmaster at jamescobban.net> Date: 2021-07-22  10:16 p.m.  (GMT-04:00) To: qgis-user at lists.osgeo.org Subject: [Qgis-user] Building Historical Maps I am running a project to present historical information about Ontario, Canada.  To support this I have imported GIS information on administrative boundaries from the Ontario Government.  The only problem is this information only describes the current administrative organization of the province, not the organization it had for most of its history up until the early 1990s when the system was "rationalized".  I am looking for suggestions of how to extract as much information from the current GIS data as possible.For example:  From 1850 to the early 1990s most of Ontario was administered as counties with lower level townships.  In the 1990s the more urbanized portions of the province were reorganized as "Regional Municipalities" which largely ignored the old county boundaries either by including only the urban portion of a former county, or by incorporating urban portions of multiple counties. So, for example, if I wish to reconstruct the boundaries of the former county of Welland I have to concatenate the boundaries of the individual townships that made up the former county, and then remove all of the internal, and redundant, boundaries.  I have manually done that for one county but it was a pain in part because the polygons of the individual townships did not begin at a "corner" shared with an adjacent township within the county. Just finding exactly where the polygon began and which direction it went took time.The second issue is that boundaries changed multiple times over the period between 1763 when Britain assumed control of the area of Ontario, and the present.  In particular city boundaries change as areas are transferred from the surrounding rural municipalities to the city as a result of urban growth.  Where do I get the old boundary information aside from tracing them from old maps?-- James Cobban911-500 Springbank DrLondon, ON, CanadaN6J 4G6mailto: webmaster at jamescobban.net+1-226-504-7603_______________________________________________Qgis-user mailing listQgis-user at lists.osgeo.orgList info: https://lists.osgeo.org/mailman/listinfo/qgis-userUnsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
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