Multimap Open API V1.2 Web Services Documentation - Coordinate Transformation

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Coordinate Transformation Overview

Many of the more widely-used online mapping APIs, including the Multimap Open API and the Microsoft Virtual Earth API, do not support the Ordnance Survey (OS) grid references, Ordnance Survey National Grid (OSNG) coordinate system or Mercator coordinates internally but do support latitude and longitude. The commonly-available algorithmic conversion methods from OS grid references or OSNG eastings and northings or Mercator to World Geodetic System 84 (WGS84) latitude and longitude are too inaccurate to use for street-level placement of locations (and are often out of alignment by more than 100 meters).

Multimap's REST API supports single or multiple eastings and northings pairs (x and y coordinates), pairs of WGS84 latitude and longitude coordinates and OS grid references. It offers a choice of JSON and XML output formats.

This document explains the conversion between OSNG coordinates and WGS84 coordinates via the REST API. You can also convert between Mercator coordinates and WGS84 coordinates. Additionally, the Multimap REST API enables you to convert the OS grid references to WGS84 coordinates.

The Multimap API now enables you to convert between OSNG coordinates and Mercator coordinates and WGS84 coordinates. For details, please see the Multimap Open API V1.2 JavaScript Coordinate Transformation documentation.

Coordinate Transformation Parameters

The Coordinate Transformation parameters, description and values are as follows:

[Note: Please replace "parameter_[COUNTER]" by incremental numbers such as parameter_1 or parameter_2.]

Coordinate Transformation Examples

Conversion from a Mercator x and y coordinate pair to a WGS84 lat and lon coordinate pair

In the following example, the Multimap REST API converts three Mercator coordinate pairs to WGS84 coordinates of latitude and longitude and gives the result in JSON output format.

JSON output:

http://developer.multimap.com/API/convert/1.2/[api_key]?output=json&system=mercator&x_1=523000&y_1=212324&x_2=323000
&y_2=212324&x_3=423000&y_3=212324

The URL returns the following response:

{"result_set":[{"point":{"lat":"1.90699","lon":"4.69819"}},
{"point":{"lat":"1.90699","lon":"2.90156"}},
{"point":{"lat":"1.90699","lon":"3.79987"}}]}	

Conversion from a WGS84 lat and lon coordinate pair to a Mercator x and y coordinate pair

In the following example, the Multimap REST API converts three WGS84 coordinate pairs of latitude and longitude to Mercator x and y coordinate pairs and gives the result in XML output format.

XML output:

http://developer.multimap.com/API/convert/1.2/[api_key]?output=xml&system=mercator&lat_1=51.79605&lon_1=0.217777
&lat_2=51.80424&lon_2=3.11815&lat_3=51.80909&lon_3=1.66779

The URL returns the following response:

<?xml version="1.0" encoding="UTF-8" ?> 
<Results xmlns="http://developer.multimap.com/API" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xsi:schemaLocation="http://developer.multimap.com/API http://developer.multimap.com/Schema/convert_1.2.xsd">
 <Point>
  <X>24243</X>
  <Y>6763332</Y> 
 </Point>
 <Point>
  <X>347111</X>
  <Y>6764807</Y> 
 </Point>
 <Point>
  <X>185658</X> 
  <Y>6765680</Y> 
 </Point>
</Results>

Conversion from an OSNG x and y coordinate pair to a WGS84 lat and lon coordinate pair

In the following example, the Multimap REST API converts three OSNG x and y coordinate pairs to WGS84 coordinate pairs of latitude and longitude and gives the result in JSON and XML output formats.

JSON output:

http://developer.multimap.com/API/convert/1.2/[api_key]?output=json&system=osng&x_1=523000&y_1=212324&x_2=323000&y_2=212324
&x_3=423000&y_3=212324

The URL returns the following response:

{"result_set":[{"point":{"lat":"51.79605","lon":"-0.21777"}},
{"point":{"lat":"51.80424","lon":"-3.11815"}},
{"point":{"lat":"51.80909","lon":"-1.66779"}}]}

XML output:

http://developer.multimap.com/API/convert/1.2/[api_key]?output=xml&system=osng&x_1=523000&y_1=212324&x_2=323000&y_2=212324
&x_3=423000&y_3=212324

The URL returns the following response:

<?xml version="1.0" encoding="UTF-8"?>
<Results xmlns="http://developer.multimap.com/API" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xsi:schemaLocation="http://developer.multimap.com/API http://developer.multimap.com/Schema/convert_1.2.xsd">
  <Point7>
    <Lat>51.79605</Lat>
    <Lon>-0.21777</Lon>
  </Point>
  <Point>
    <Lat>51.80424</Lat>
    <Lon>-3.11815</Lon>
  </Point>
  <Point>
    <Lat>51.80909</Lat>
    <Lon>-1.66779</Lon>
  </Point>
</Results>

Conversion from an OSNG x and y coordinate pair and a grid reference to a WGS84 lat and lon coordinate pair

In the following example, the Multimap REST API converts two OSNG x and y coordinate pairs and a grid reference to WGS84 coordinate pairs of latitude and longitude and gives the result in XML output format.

XML output:

http://developer.multimap.com/API/convert/1.2/[api_key]?output=xml&system=osng&x_1=523000&y_1=212324&x_2=323000&y_2=212324
&grid_3=NN166712

The URL returns the following response:

<?xml version="1.0" encoding="UTF-8" ?>
<Results xmlns="http://developer.multimap.com/API" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://developer.multimap.com/API http://developer.multimap.com/Schema/convert_1.2.xsd">
  <Point>
    <Lat>51.79605</Lat>
    <Lon>-0.21777</Lon>
  </Point>
  <Point>
    <Lat>51.80424</Lat> 
    <Lon>-3.11815</Lon> 
  </Point>
  <Point>
   <Lat>56.79607</Lat> 
   <Lon>-5.00470</Lon>
  </Point>
</Results>

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