Does Y mean latitude and X mean longitude in every GIS software?
I am using Mapinfo and it has Y as latitude and X as longitude. Is that the same case for all mapping software? As for any country their respective value is multiple of 1 or -1. So for Nepal can I say it is on positive side +1 for both latitude and longitude? And for USA to be +1 Y and -1 X.
Latitude is the Y axis, longitude is the X axis. Since latitude can be positive and negative (north and south of the Equator), and longitude can be as well (negative west of Greenwich and positive eastward) when the -180 to +180 longitude system is use. Hence the four combinations of positive and negative are possible depending upon where you are located on the globe.
You will appreciate an earlier thread that discusses this question more generally: http://gis.stackexchange.com/questions/6037/latlon-or-lonlat-whats-the-right-way-to-display-coordinates-and-inputs.
Surely the mathematical x,y axes are at right angles to each other. Latitude & longitude are not.
@user84263 - in a *Euclidean* geometry, axes are at right angles, and lines that are constant in one coordinate are all at right angles to lines of the other coordinate. On a non-Euclidean surface, as you point out, this cannot be the case. Nevertheless, a spherical or ellipsoidal surface can be defined by two coordinates, call them x/y or longitude/latitude as you wish. Begin at a given point on the surface, and rotate that point independently around two perpendicular axes of rotation. This yields a pair of "axes". Along one axis, x is zero. Along the other axis, y is zero.
No, for example when talking to a GeoServer WFS (or any other compliant WFS) the axis order depends on if you ask for version 1.0 or 1.1 of the spec in EPSG:4326.
The original spec had longitude,latitude order. This is more of a software-oriented view as it matches up with [US-centric] x,y order. This doesn't match the ISO standard, so various later specs have changed the order to latitude,longitude. This order should be used when displaying or transmitting the values, they don't have to be stored that way. Not everyone uses x,y as the labels for easting,northing. Some people use y=easting,x=northing. For projected data, the coordinate reference system defn should specify the axis order and labels.
@mkennedy Although the US convention may be (long, lat), that does not make such a convention "US-centric." This actually is the *international* and very long established convention in mathematics and physics. It is based on the concept of orientation of a coordinate system in which (long, lat) agrees with the conventional positive (x,y,z) orientation of 3D Cartesian coordinates when an outward-pointing normal direction (*i.e.*, "up") is used for the third coordinate on the sphere.