# What type of coordinates?

I was given homework to covert this to some location on planet earth. But I am unable to make sense over these numbers....

Tried various forms of coordinates representation but still no clue...

15855946.63 / -4587472.23

Numbers that big are going to be small units like metres or feet.

The earth circumference is about 40,000,000 m, so your numbers might be about 15,000,000m east and 4,500,000m south of some origin point.

The most common coordinate reference used these days is Google's Web Mercator system. I can use `R` to see where your point is in latitude-longitude:

``````> library(sf) # spatial features package
``````

Make a point at that location:

``````> pt = st_point(c(15855946.63 ,-4587472.23))
``````

Try the google mercator coordinate system (code 3857):

``````> pts = st_sfc(pt, crs=3857)
``````

See where that is in lat-long (code 4326):

``````> st_transform(pts, 4326)
Geometry set for 1 feature
geometry type:  POINT
dimension:      XY
bbox:           xmin: 142.4364 ymin: -38.05694 xmax: 142.4364 ymax: -38.05694
epsg (SRID):    4326
proj4string:    +proj=longlat +datum=WGS84 +no_defs
POINT (142.4364 -38.05694)
``````

So that's 142 degrees east and 38 degrees south of where the equator meets the greenwich meridian.

If I then put "142.4364E 38.05694S" into Google Maps that gets me to a point outside Minjah in southern Australia.

Note this is not a unique or perfect solution. Those numbers could be any of many other coordinate reference systems, or be in feet, or furlongs, or degrees multiplied by a million. Its a dumb question and if that's all the teacher asked you then you're not being taught very well.

If this is homework then I'll relate a tale a great teacher told me about his education. His class was told to do something for homework. The next day anyone who got the answer wrong was whacked with a cane. Anyone who got the answer right, but couldn't explain how, was whacked with a cane twice. If your teacher asks how you got this answer, please give them a link to this page.