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I have a map of Nova Scotia published by the Department of the Interior Canada in 1924 which I would like to georeference.

The map has a graticule labeled with latitude and longitude. According to a note on the map, the prime meridian is Greenwich. It's not a Conformal projections since lat/long do not meet perpendicular.

I have read that the Department of the Interior Canada was using a Polyconic projection before replaced with the 1932 Lambert Conformal Conics. (https://www.asprs.org/a/resources/grids/12-97-canada.pdf)

Were there other projections used in 1924? What projection and datum is most likely used for a map of Nova Scotia in 1924?

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Polyconic seems to me with good chances.

In this document: https://pubs.usgs.gov/pp/1453/report.pdf, page 106, more details about the polyconic projection.

Usage: The sole projection used for large-scale mapping in the ellipsoidal form (topographic quadrangles) of the United States by the U.S. Geological Survey until the 1950's Basis for Progressive Military Grid used by the U.S. Army until the 1940's Projection for many early coastal charts by the U.S. Coast and Geodetic Survey
Origin: Apparently originated about 1820 by Ferdinand Rudolph Hassler (1770-1843), first director of the Survey of the Coast (later the U.S. Coast and Geodetic Survey)

Here a map of Nova Scotia, 1924, found at: http://rumseysid.lunaimaging.com/mrsid/mrsid_images/Rumsey/SIDS/D5005/5028155.sid?image=/D5005/5028155.sid (286MB), seems to have the central meridian at -64 degrees (approx.).

map1

Here a OSM map with a 1 degree grid, reprojected to +proj=poly +lon_0=-64 +datum=WGS84 +no_defs:

map2

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