Diff: CoordinatesFAQ

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

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-### Index ### 

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-! 1. Use the web to find your location 

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

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-(http://services.land.vic.gov.au/landchannel/content/interactivemap http://services.land.vic.gov.au/landchannel/content/interactivemap) 

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-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: 

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-{http://users.bigpond.net.au/flett/wireless/InteractiveMap.jpg EXAMPLE: Interactive Map Coordinates Bar} 

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

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-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'''. 

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-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. 

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

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-! 2. Convert DMS coordinates to Decimal Degrees 

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-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. 

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

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-(http://www.geology.enr.state.nc.us/gis/latlon.html http://www.geology.enr.state.nc.us/gis/latlon.html) 

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-Here is an example of how to use it: 

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-{http://users.bigpond.net.au/flett/wireless/DMStoDd.jpg EXAMPLE: DMS to Dd converter} 

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-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. 

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-! 3. Convert GDA94 coordinates to AGD66 coordinates 

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-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. 

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-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 (http://www.nodedb.com NodeDB) wireless node database.  But LocFinder uses AGD66 coordinates. 

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-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: 

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-(http://www.land.vic.gov.au/land/lcnlc2.nsf/childdocs/-418EED712A81C5AE4A256A0A0015CDC1-5DF1E2E5B878F6634A256A0A001DAC5C-5B923E73477D6D65CA256E5F0013D73B-E2E957070C9269184A2568B60015AC7B?open GDA94-AGD66 Conversion Tool) 

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-Here's an example of it's use: 

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-{http://users.bigpond.net.au/flett/wireless/GDA94toAGD66.jpg EXAMPLE: Converting GDA94 to AGD66} 

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-This is the result: 

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-{http://users.bigpond.net.au/flett/wireless/AGD66Coords.jpg EXAMPLE: Converted coordinates} 

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-! 4. Enter AGD66 coordinates into LocFinder 

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

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-(http://melbourne.wireless.org.au/nodes/create http://melbourne.wireless.org.au/nodes/create) 

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-(or edit your existing node) 

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

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-{http://users.bigpond.net.au/flett/wireless/LocFinderEntry.jpg EXAMPLE: Entering coordinates into Locfinder} 

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-5 decimal places is more than adequate for LocFinder 

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

+See the CoordinatesHowto for lots of info.