Hi Javier, By convention, geodetic coordinates are Latitude, Longitude (ϕ,λ). If you project ϕ,λ onto a plane (in the most natural way), you get Northing, Easting. Which then leads to the X = North, Y = East convention.
As an example of a SW coordinate system, consider South Africa. See https://ngi.dalrrd.gov.za/index.php/resources?download=37:the-south-african-coordinate-reference-system : *5.1.2 Latitude at natural origin /reference Latitude:* - 5.1.2 The equator 0°E, is the latitude of reference or origin of the Gauss Conform Coordinate System. *5.1.3 x (southings)* - Coordinates are measured southwards from the equator - Increases from the equator (where x = 0m) towards the south pole (with a maximum of ± 3 840 000m for continental South Africa). - Similar to the “northing” coordinates but sign in opposite. *5.1.4 y (westings)* - Coordinates are measured from the Central Meridian (Lo) of the respective zone. - Increases from the CM (where y=0) in a westerly direction. - “y” is +ve west of the CM and –ve east of the Central Meridian. Regards, Nick. On Thu, 2 May 2024 at 10:05, Javier Jimenez Shaw via PROJ < [email protected]> wrote: > Yes, of course it is the local convention (more on that later). My > question is if anybody knows why those local conventions. > > For me, to denote coordinates mathematically in a Cartesian plane, the > natural order is x,y. (How we studied at school). With the X positive axis > going to the right, and Y positive axis to the top of the page. > Doing that with Cartesian coordinates in a map I would expect the same. > And it is the most common convention (easting-northing) > However, in some cases the ordering is northing-easting. Probably due to > historical reasons. I would like to know those reasons. > Those maps are displayed with north at the top of the map. You have to go > really back in time to see printed (or more probably painted) maps with the > East or the South on the top (I never saw West, but probably there are). > > Of course people can do whatever they want (and usually do). I am > interested on the reasons for those different criteria. Is the influence of > this or that cartographer? Or in eastern countries? Or by this or that > language? Maybe a scientist did that following some mathematical tradition > I don't know? Is it to have numbers in an easier way to read? Or is it > simply to make our life more complicated and error prone? Probably there is > not a single explanation, but many. I know there are geodetists in this > group with much more experience and knowledge than me. > > About local conventions, as I say later in the mastodon thread, local > usage is not always following the axis order. > For instance, in USA almost every surveyor uses PNEZ order for GCPs (point > id, northing, easting, elevation), but all the official CRSs in USA are > Easting-Northing. > Similarly in Argentina, the official projected CRS is Northing-Easting, > but some (many?) surveyors use Easting-Northing. > > About following the same criterion as in Latitude-Longitude, it is an > option. But for me it is just a guess. I do not have any data. And > geographic coordinates were not always mentioned in that order. I just > learned reading Snyder that Mercator wrote in 1569 "... quam secundum > longitudinem latitudinemque debitam..." > https://en.m.wikipedia.org/wiki/Mercator_1569_world_map#legend3 (I don't > speak Latin. Maybe the order is reversed due to any strange grammar rule). > > Cheers. > Javier. > > > On Wed, 1 May 2024 at 12:06, Martin Desruisseaux via PROJ < > [email protected]> wrote: > >> Le 2024-05-01 à 11 h 42, Javier Jimenez Shaw via PROJ a écrit : >> >> > Question: >> > Do you know why some **projected** coordinate reference systems use >> > axis order Northing-Easting? >> > Is that a historical reason? >> >> If I remember correctly, Roger Lott from EPSG told me that it was >> reflecting the local convention of the country that defined the >> projected CRS. The abbreviation as well, even if "X" is sometime used >> for Northing (for example), it, this is because the country that defined >> the projected CRS does that way. >> >> In some way, the EPSG database can be seen as not only a database of CRS >> and coordinate transformations relating them, but also a database of the >> local conventions for each country. In some way, the CRS contains >> localization data. >> >> Martin >> >> >> _______________________________________________ >> PROJ mailing list >> [email protected] >> https://lists.osgeo.org/mailman/listinfo/proj >> > _______________________________________________ > PROJ mailing list > [email protected] > https://lists.osgeo.org/mailman/listinfo/proj >
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