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CoordinatesHowto

This FAQ shows you how to find your location for use in our online maps (LocFinder) in one easy step.

  1. Use the External linkGPS Lookup facility and enter your address details, after a short delay (about 5 seconds) you will be shown you a map confirming the location you specified. Use the latitude and longitude given to you above the map.


Below is the OLD howto entry, useful if the above method doesn't work for you.

This FAQ shows you how to enter your location into the LocFinder node mapping database in four easy steps:


1. Use the web to find your location


For Victorian users, find your coordinates on the Victorian Government's Land Channel Interactive Map

External linkhttp://services.land.vic.gov.au/landchannel/content/interactivemap

When zoomed right in, the map will show individual property boundaries, with street numbers. Find your location and look at the bottom left corner of your browser window:

EXAMPLE: Interactive Map Coordinates Bar

You need to use the coordinates marked as "Geographicals" - these are your Latitude and Longitude, respectively.

Note that these coordinates are in the format DEGREES, MINUTES, SECONDS.FractionsOfSeconds
You can not enter these coordinates into LocFinder directly!
The LocFinder node database only accepts coordinates as Decimal Degrees.

Fractions of Degrees have traditionally been expressed as Minutes and Seconds. One Minute is one 60th of a Degree and one Second is one 60th of a Minute. Fractions of a second are usually written as a decimal fraction.

In the above example our Latitude is 37 Degrees, 19 Minutes and 53.5 Seconds South (of the Equator).

2. Convert DMS coordinates to Decimal Degrees


Decimal Degrees simply use a decimal fraction to express fractions of a degree. The Latitude in the above example is -39.33153 when expressed as a Decimal Degree. Latitudes south of the Equator are expressed as negative numbers.

You can use this online tool to convert coordinates in Degrees,Minutes,Seconds (DMS) format to Decimal Degrees:

External linkhttp://www.geology.enr.state.nc.us/gis/latlon.html

Here is an example of how to use it:

EXAMPLE: DMS to Dd converter

Note that this tool returns the wrong coordinates if you enter your degrees as negative degrees. Keep everything positive and add the negative sign to the Latitude afterwards.

3. Convert GDA94 coordinates to AGD66 coordinates


OK, now you have your coordinates in Decimal Degrees format. You could enter these coordinates into LocFinder now but your node would appear about 200 metres Southeast of your real location.

Why? Because, to make matters more complicated, there are two major coordinate systems in use in Victoria today - the newer GDA94/WGS84 system and the older AGD66 system. These coordinate systems differ from each other by about 200 metres. The GDA94 system is being introduced into all Australian Government mapping products and is based on the worldwide standard (WGS84) for GPS receivers. The Victorian Land Channel website that we just used to get our coordinates uses GDA94 coordinates, as does the External linkNodeDB wireless node database. But LocFinder uses AGD66 coordinates.

So now we need to convert our decimal GDA94 coordinates to decimal AGD66 coordinates. The Victorian Land Channel website has a tool to do just that:

External linkGDA94-AGD66 Conversion Tool

Here's an example of it's use:

EXAMPLE: Converting GDA94 to AGD66

This is the result:

EXAMPLE: Converted coordinates

4. Enter AGD66 coordinates into LocFinder


Finally we have numbers that we can directly enter into LocFinder. If you're not there already, go to the Node Creation page.

(or edit your existing nodes)

And enter your coordinates (AGD66 Decimal Degrees) like so:

EXAMPLE: Entering coordinates into Locfinder

5 decimal places is more than adequate for LocFinder

Your node should now hopefully show up in the right location in LocFinder


Version 3 (current) modified Tue, 03 Jul 2007 23:11:57 +1000
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