[PROJ] Easting-Northing vs Northing-Easting

[Nick Mein]

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 <
proj at lists.osgeo.org> 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 <
> proj at lists.osgeo.org> 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
>>
>>
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