iMapPlot Co/ords

Submitted: Thursday, Aug 05, 2004 at 21:09
ThreadID: 15326 Views:1901 Replies:2 FollowUps:2
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Useing iMapPlot on this site,it shows the town I live in at certain coordinates,yet if I go outside and useing my GPS,tracking 8 sats,it gives me a coordinate 33kms away.So,is the iMapPlot not real accurate or my GPS?
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Reply By: Greg Harewood - Friday, Aug 06, 2004 at 10:13

Friday, Aug 06, 2004 at 10:13
Nick - The GPS, unless malfunctioning, is unlikely to be more than 50 or so metres out and in ideal conditions will be within 5 metres of your "correct" coords. The coords will of course not exactly match but 33km's is excessive unless the town you are refferring to is big (eg Sydney:). How big is the town you live in? How far away is the PO/centre of the town. Assuming you are within a few kms of where it should be plotting I suspect, ignoring a few other possibilities, that the town is being plotted in the wrong spot on iMapPlot. This could be due to the raw data being incorrect/inaccurate (ie GeoScience Australia data) or some bug in the map making process. Dave is of course the only one who can sort this out. What town are you referring too and what are the two different coords you are getting?

Cheers
Greg
I sent one final shout after him to stick to the track, to which he replied “All right,” That was the last ever seen of Gibson - E Giles 23 April 1874

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Follow Up By: Member - Nick (TAS) - Friday, Aug 06, 2004 at 18:23

Friday, Aug 06, 2004 at 18:23
Thanks Greg,Very small town Chudleigh,about 100 odd people.My GPS gives me -41 3327 146 2843, iMapPLOT gives -41 5572 146 4792.
Nick
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Reply By: Greg Harewood - Friday, Aug 06, 2004 at 19:51

Friday, Aug 06, 2004 at 19:51
Nick – Problem solved – the iMapPlot data is in decimal degrees and the readout on your gps is degrees, minutes and seconds – the iMapPlot cords -41.5572° 146.4792° represent 41° 33’ 26” 146° 28’ 45”.

The coords form your GPS (41° 33’ 27” 146° 28’ 43”) are actually only about 60m away from the Geoscience Australia coords for your town which is quite amazing!!

GPS units normally have option to show coords in decimal degrees (along with degrees minutes or degrees, minutes and seconds) so you should be able to change your GPS display readout to match iMapPlot if you wish to avoid confusion in the future.

If you want to do it manually just divide the seconds by 60, add this figure to the minutes then divide by 60 again and add the resulting figure to the degrees eg for 41° 33’ 26”…26 divided by 60 = 0.4333, plus 33 = 33.4333, 33.4333 divided by 60 = 0.5572. Then add degrees (41) = 41.5572°…easy :)

Just another thing to keep in mind when playing around with coords from other sources.

Cheers
Greg
I sent one final shout after him to stick to the track, to which he replied “All right,” That was the last ever seen of Gibson - E Giles 23 April 1874

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Follow Up By: Member - Nick (TAS) - Friday, Aug 06, 2004 at 22:12

Friday, Aug 06, 2004 at 22:12
Thanks again Greg,checked GPS and it dosnt have the decimal degrees option.Got a bit more to learn with the GPS yet. Nick
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