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# Conversion accuracy from (latitude, longitude) to (x,y) by utm_odometry_node

I wrote node for subscribing to the odom topic(nav_msgs/Odometry) at which utm_odometry_node publish results of conversion from (latitude, longitude)(degres)to (x,y)(meters). So my question is is that conversion to (x,y) valid? (I use C Turtle.Code of node who is sunscribing to odom topic is here in answer of my orevious question: http://answers.ros.org/question/485/u... )

Example: That gives gpsd_client: (coordinates in Croatia, nortwest) latitude: 46.3954 longitude: 16.448 That gives utm_odometry_node: x:611320 y:5.139e+06 I think that in x coordinate one digit is missing. Well if someone is working with utm_odometry_node and know something about conversion(accuracy, problems, etc.),please let write answer. Thanks

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That is probably a correct output.

You have to remember that UTM is in reference to some fixed point on a grid. If you are significantly closer in the x direction, then it is totally reasonable that the x coordinate will be powers of 10 smaller than the y coordinate.

As a quick sanity check, I use the Geotool: For your coordinates

This gives you UTM coordinates: 33T 611320 5138999, which seems to be in line with the ones that you got with the UTM odometry node. The first digits represent the zone that you are in, which you can look up on a map like the following. The next numbers describe your position, in reference to a central meridian plus a "false northing" and "false easting" to insure that negative numbers will never be a possibility.

You may want to read up a bit more on UTM, Wikipedia has a really good explanation of the reasoning behind UTM.

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Thanks for your answer. I looked at wikipedia UTM and i read about UTM coordinate system. I was using some version Gaus-Kruger conversions which gave me another results ( i was using for that geodetic GPS-RTK instead my GPS form Locosys) so i was thinking that conversions to UTM is false.
( 2011-03-24 23:06:36 -0500 )edit
And thanks for useful tool geohack, i found that page with link https://jira.toolserver.org/browse/GEOHACK (http://toolserver.org/~geohack/).
( 2011-03-24 23:08:50 -0500 )edit