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Is there a way to search for highway mile markers on an existing mapping system and find the lat and lon?

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you need to provide more info. Google Maps does not provide this for starters. –  Simon Apr 23 '11 at 0:47
    
ok, what I mean is can I put in something like "highway 36 mile marker 26.74, lassen county ca" and get the lat and lon? –  user2755 Apr 23 '11 at 1:20
    
obviously I tried this on Google maps already, is there something else? –  user2755 Apr 23 '11 at 1:20
    
If you have your dataset in a PostGIS database, you can use the ST_Line_Interpolate_Point postgis.refractions.net/documentation/manual-1.5/… function to find any point along a linestring, but I don't know if there are any datasets with specific mile markers. –  MerseyViking Apr 23 '11 at 8:27

1 Answer 1

If you have the spatial data of the highway (e.g., a shapefile), you can use linear referencing to obtain the geographic coordinates. (E.g., see examples/docs for ArcGIS 9.3, PostGIS, Shapely).

Note that this only works if your roadworks spatial data "start" at the correct "Mile 0", and continues onward. If, for example, there were highway alignment changes, the milestones are often not moved to accommodate changes in the length of the entire highway. Also, be aware to ensure that your input spatial data is projected (i.e., not lat/lon).

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Interesting point. In WWII, all of the railway mile markers were removed, to stop the Germans being able to navigate their way around the country (due to how the mile markers were arranged). When they were replaced after the war, they were not replaced in the right positions, they were put in place, approximately, so they're as good as tits on a bull. –  Hairy May 24 '11 at 7:53

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