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PostPosted: Sat, 22-08-09, 23:13 GMT 
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Location: France, South, not far from Montpellier
Hello folks,

I met a problem today; I need to convert some points from a doc showing a piece of land, points which seems to be in "UTM zona 20" here in Paraguay. Basically I have something like:

754056,971 N
606543,118 E

and I'd like to convert this into Google's coordinates (a quick search in Wikipedia give for Google Earth the WGS84 system for their coordinates)...

I've done a quick search for an online converter, but so far no chance...

Does anybody knows a place where I can do that easily? Or a free but accurate tool? (I have only 2 points to convert so I don't think in buying a commercial soft... :?)


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PostPosted: Sat, 22-08-09, 23:31 GMT 
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Christophe,

I don't understand even your starting coordinates. What's their range and dimension?? Normally coordinates range as follows:

latitude: -90 ..+90 degrees, longitude 0..360 degrees.

Without knowing how your input coordinates are defined it is not possible to convert them.

Fridger

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PostPosted: Sun, 23-08-09, 12:35 GMT 
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t00fri wrote:
Christophe,

I don't understand even your starting coordinates. What's their range and dimension?? Normally coordinates range as follows:

latitude: -90 ..+90 degrees, longitude 0..360 degrees.

Without knowing how your input coordinates are defined it is not possible to convert them.


That's my problem!
Anyway in the UTM wikipedia page we can read:

Quote:
As an example, the CN Tower is located at the geographic position 43°38′33.24″N 79°23′13.7″W. This is in zone 17, and the grid position is 630084m east, 4833438m north. There are two points on the earth with these coordinates, one in the northern hemisphere and one in the southern. In order to define the position uniquely, one of two conventions is employed:
Append a hemisphere designator to the zone number, "N" or "S", thus "17N 630084 4833438". This supplies the minimum additional information to define the position uniquely.
Supply the grid zone, thus "17T 630084 4833438". The provision of the grid zone supplies redundant information (which may, as a consequence, be contradictory).
Because latitude band "S" is in the northern hemisphere, a designation such as "38S" is ambiguous. The "S" might refer to the latitude band (32N – 40N) or it might mean "South". It is therefore important to specify which convention is being used, e.g., by spelling out the hemisphere, "North" or "South".


So that seems to fit pretty well; Paraguay must be UTM zone 20 S, and my coordinates could be in meter East and North like the above example.
Now, how can one convert this to the Google annotation?? (also used in GPS if I'm not wrong...)


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PostPosted: Sun, 23-08-09, 13:04 GMT 
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Hi Christophe

I found some data about UTM system here : http://www.uwgb.edu/dutchs/FieldMethods/UTMSystem.htm
and a very usefull conversion spreadsheet : http://www.uwgb.edu/dutchs/UsefulData/U ... sions1.xls (use Main Page sheet)

Regarding this data your northing value seems to be incorrect .
For utm zone 20 in paraguay northing value should be between 7 300 000 and 7 900 000

Sorry for my bad english
I'm just a Frenchie in ..... France

Yo


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PostPosted: Sun, 23-08-09, 14:15 GMT 
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Salut Yo!

Un grand merci pour ces docs, et principalement pour la feuille de calcul.

I have no idea yet why the northing is missing a digit but indeed that makes a difference! :lol:
I'll have to check with the landing register guy on monday.

Again a big merci, and don't worry for your English, cannot be worst than mine! :wink:

A+

(BTW, welcome to CM! :D)


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PostPosted: Mon, 24-08-09, 17:18 GMT 
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Problem solved!

I went for this digit problem to the landing register and indeed was a typo!
So the right coordinates were:

7540562,971 N
606543,118 E

Now, after checking both in Google and in their system, seems we have a small difference (around 10m), but as those points are in middle of nowhere, north to the tree after the monkey, who cares? ;)

Tx again Yo, Tx also to the author of the conversion spreadsheet, Mr Steve Dutch from the University of Wisconsin-Green Bay.


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