Projections are about how the three dimensional earth is represented in two dimensions, and they can get very complicated; for example:
- latitude and longitude may be in that order, or in the reverse order
- they may be in decimal degrees or in metres
- they may use various places as their zero points
The way I think of it is
- Longitude is West to East, and in mathematical terms it is the x-axis
- Latitude is South to North, and in mathematical terms it is the y-axis
- Geographers tend to put Latitude first, Mathematicians tend to put Longitude first
The possible formats when M4OPS is used to output coordinates are:
| Name | Description | Comment | Example, using the centre of Needingworth |
| No lat/lon click | Does not generate coordinates | Default | N/A |
| M4OPS lon;lat csv | Like EPSG:4326 in degrees
but longitude first | Uses semi-colon rather than comma
generally used for input into M4OPS | -0.0322822;52.3304203 |
| M4OPS parameters | In degrees | In a format suitable to append to a URL | &Lon=-0.0322822&Lat=52.3304203 |
| lat,lon csv | Latitude first, in degrees | 'EPSG:4326' | 52.3304203, -0.0322822 |
| {lon,lat} GeoJSON | Longitude first, in degrees | In computer friendly GeoJSON format | [-0.0322822, 52.3304203] |
| EPSG:3857 (x/y) | Longitude first, in metres | Used internally within M4OPS | -3593.9420062, 6860091.7465739 |
| DegMinSec N/E | Latitude first
Northing and Easting | Traditional degrees
minutes and seconds | 52° 19′ 50″ N 0° 01′ 56″ W |
| GeoHack links | Open a GeoHack window | Shows many mapping,
aerial, wiki, photo
and other resources | GeoHack link |
Note that, in case it is used for very local mapping, M4OPS outputs 7 decimal points, which for degrees is about 1 cm - the practical limit of commercial surveying (
https://en.wikipedia.org/wiki/Decimal_degrees)
If you want to locate a place in M4OPS that you have found in Google Maps, then the easiest process seems to be:
- in Google Maps zoom right in to the place you are interested in
- in your browser's address bar locate a string like /@50.9635263,-4.2593133,15z/ (note the 15z may be 16z or 17z - it is the zoom
- copy the part of this string between the /@ and ,15z/ (ie 50.9635263,-4.2593133) - these are the coordinates of the bottom left of the window
- in M4OPS click on the Go to button at top right
- paste in the coordinates you have copied and M4OPS should move to the specified location
- (Hint: using the Bing Aerial with Labels layer you can see the names of places to check you are where you expect to be)
For more on projections and other mapping subjects see the links in
Useful background on Web Mapping.
