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Limitations & Disclaimer

There is inherent inaccuracy in any coordinate transformation and while every effort
has been made to make the transformations performed on this page as accurate as
possible, there are likely to be degrees of error, depending upon the transformation
and Coordinate Reference Systems (CRS) which are selected. The amount of error can
be as little as 1-2 metres in some cases, or unknown in others. Note that not all
combinations of CRS transformations have been tested. Realitygeo Ltd accepts no
liability for any errors and inaccuracies in converted coordinates delivered by
this page.

Note also that although the majority of global CRS and transformations
are represented on this page, some are missing because of difficulties in determining
the transformation or establishing parameters, and with many combinations of CRS
there are no parameters to convert between them, so any conversion is impossible.
For comprehensive information on all CRS and transformations known worldwide visit

EPSG Geodetics. A
good reference for understanding why there is error in any coordinate conversion,
and information about CRS in general, is

this document from the Ordnance Survey, which although focusing
on the British Isles, contains a well written and easy to follow explanation of
global CRS and transformations.

For feedback and further information email

here.
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Instructions

Well, it's pretty straightforward ..

FIRST choose the systems you wish to convert between by typing in the search fields,
then select a CRS from the list. The left search text contains a list of projected
coordinate systems (termed Grids for simplicity) that represent a graph like interpretation
of representing coordinates on a rectangular section of The Earths' surface. Grid
coordinates are represented as X and Y values, and are usually in metres, although
there are some exceptions. Once selected, the Grid details are shown, which includes
this unit of measure, and also the conversion parameters, e.g. False Easting, Northing,
and Latitude and Longitude Origins which are used to convert Grid coordinates to
Latitude and Longitude values. Note that each Grid is BASED on a geographic coordinate
system, details of which are included below the Grid parameters.

The right search text contains a list of geographic coordinate systems (termed Graticules
for simplicity). In its simplest terms just think of the Graticule as an attempt
to model The Earth. The Earth isn't perfectly rounded and there are fluctuations
in gravity and mean sea level etc, over the centuries numerous individuals have
attempted to mathematically model The Earths dimensions, and these are represented
as geographic coordinate systems. Geographic coordinates are represented as Latitude
and Longitude values. Once selected, a few parameters of the Graticule are displayed,
such as the A and B values (earths horizontal and vertical radii respectively in
metres) and its flattening, which represents a ratio between A and B, i.e. in simple
terms how much the Graticule is soccer ball shaped or rugby ball shaped.

Initially the page is setup to convert between the British National Grid and WGS84.

THEN when you select a CRS, the map will update with an orange bounding box for
the EPSG area for that Grid, and it will add as the initial coordinate the center
Latitude and Longitude as a blue dot.

Note that the map data is in the simple CRS 3857, the Pseudo Mercator (based on
the WGS84 Graticule), and as such coordinate accuracy is better reflected closer
to the intersection of the Equator and the prime meridian at Greenwich, London (blue
lines on the map). Map navigation is straightforward, note PC users can hold the
shift key and left mouse to box zoom.

At the bottom of the page, these initial coordinates representing the center point
of the grid selected (as shown on the map) are filled out in the 3 boxes for coordinate
pairs. On the left we have the grid X and Y in map units. In the middle we have
the Latitude and Longitude values for the Graticule which the Grid is BASED on.
And on the right the transformed Latitude and Longitude values in the chosen Graticule
(Obviously if the two Graticules are the same the coordinates will be identical!).

NB: Some conversions are not possible because parameters don't exist or the transformation
is unsupported. For example OSNI 1952 / Irish National Grid (29901) to NAD83 (4269).
When this occurs the bottom right input details for the Graticule will be greyed
out. You can still however convert between X and Y and Latitude and Longitude values
for the Graticule the Grid is based on.

HOW TO CONVERT: This can be done in a few ways ..

1) Type new X and Y values in the boxes bottom left and hit the 'Convert' button
or return key.

2) Type new Latitude and Longitude values in either the center bottom or bottom
right pairs of text boxes and hit the 'Convert' button or return key. Note that
on entering data in the Latitude or Longitude the value will update as decimal degrees
in the boxes, but display as degrees, minutes and seconds on labels beneath also.
The text boxes are smart, so you can enter decimal degrees in them or degrees, minutes
and seconds (e.g. 54° 39' 36.00", or -5° 9' 25.00", using a minus sign - as degrees
South or West) and they will accept it, in fact, if you choose to just enter numbers
separated by spaces as degrees minutes and seconds it will understand this too (e.g.
54 39 36, or -5 9 25).

3) Click/Tap on the map! This will convert that point.

4) Use the circular button top right of the map to convert Your Location (if it
is enabled on your computer and web browser - search 'enable geolocation' for more
information). Obviously if you are not located within the chosen Grid area you will
get some odd X and Y values.