GPS guru's help needed !!
Submitted: Thursday, Jul 16, 2009 at 13:27
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Member - Pedro the One (QLD)
Hi ....
I have this problem to solve :
I run a Garmin GPS60 and the brother has an Eagle SportsMap 100.
We have both taken a mark/waypoint from EXACTLY the same position.
In overlaying them on Google Earth, my Garmin is precise whereas the Eagle shows the same mark as being 220 metres out, approx. SSW of the real position.
Both GPS's are set to WGS84, all other settings APPEAR to be compatible, yet there is thiis relatively major variation.
This difference is consistent on all waypoints ...... and whilst travelling.
We use these aids for travelling to ALLEGED goldbearing areas, following tracks gleaned from GoogleEarth. Such a variation, whilst not dangerous, does present some hazards, specifically in unknown territory.
Any assistance here would be much appreciated .... thanks !!
Reply By: Member - Andrew (QLD) - Thursday, Jul 16, 2009 at 13:57
Thursday, Jul 16, 2009 at 13:57
What's an Eagle Sportsmap 100? never heard of one.....
Andrew
AnswerID:
374793
Follow Up By: Member - Pedro the One (QLD) - Thursday, Jul 16, 2009 at 23:46
Thursday, Jul 16, 2009 at 23:46
Sorry, I think he meant an Eagle Map 100 GPS ....
FollowupID:
642166
Reply By: Member - Doug T (NT) - Thursday, Jul 16, 2009 at 14:05
Thursday, Jul 16, 2009 at 14:05
The fix is simple, tell your brother to get a Garmin GPS60 too.
.
AnswerID:
374795
Follow Up By: Member - Pedro the One (QLD) - Thursday, Jul 16, 2009 at 23:48
Thursday, Jul 16, 2009 at 23:48
Thanks Doug ....
The bro said that some-one would respond with that ...
I said .... iffen any-one did ...... it would be Doug !!!!
FollowupID:
642167
Reply By: kingswoodwagon - Thursday, Jul 16, 2009 at 14:42
Thursday, Jul 16, 2009 at 14:42
200m out in that direction is difference ive often seen between WGS84 and AGD84
AnswerID:
374801
Follow Up By: WBS - Thursday, Jul 16, 2009 at 16:12
Thursday, Jul 16, 2009 at 16:12
I have to agree. If we hadn't been told they are both set on WGS84 datum I would have immediately leapt to the conclusion that it is the difference between AGD66 and WGS 84. I can offer no other explanation either.
WBS
FollowupID:
642083
Follow Up By: Member - Pedro the One (QLD) - Friday, Jul 17, 2009 at 01:24
Friday, Jul 17, 2009 at 01:24
KWW ..........
you sayeth "difference ive often seen between WGS84 and AGD84 "
Presume you mean between WGS84 and AGD66 ???
However, both units were set to Datum WGS84, BUT ..... I will personally check the bro's unit again, to be sure.
FollowupID:
642172
Follow Up By: kingswoodwagon - Friday, Jul 17, 2009 at 07:53
Friday, Jul 17, 2009 at 07:53
They are very similar. The difference between AGD66 and AGD84 is only a few metres in northing. Stuff we dont really need to know now that GPS is around. :)
FollowupID:
642185
Reply By: Lex M (Brisbane) - Thursday, Jul 16, 2009 at 16:32
Thursday, Jul 16, 2009 at 16:32
"In overlaying them on Google Earth, my Garmin is precise whereas the Eagle shows the same mark as being 220 metres out, approx. SSW of the real position"
How exactly did you overlay them?
AnswerID:
374813
Follow Up By: Member - Pedro the One (QLD) - Thursday, Jul 16, 2009 at 23:45
Thursday, Jul 16, 2009 at 23:45
My apologies to all ....
I meant to include this image as the illustration.......
Image Could Not Be Found
We both took a 'mark' from precisely the same spot, with the two differing results.
FollowupID:
642165
Follow Up By: Member - Andrew (QLD) - Friday, Jul 17, 2009 at 00:38
Friday, Jul 17, 2009 at 00:38
Yeh, i'm with Lex here as i summise that you are entering the coordinates in Google Earth as DISPLAYED on your respective GPSrs. One is displaying coordinates using the WGS84 datum whilst the other is referencing AGD66/AUS66.
The Lowrance (GM100 i assume) GPSr is set with it's datum as "Australian Geodetic 1966" and should be changed to the datum of your map....in Google Earth's and many cases WGS84.
Another very remote possibility in these models was they had a PCF (Position Correction Factor) feature which would offset the displayed postion much like a datum shift.
The manual for the (legacy product) GlobalMap 100 which could be what you are referring to as they were very popular can be found here:
../Lowrance/Documents/Manuals/GM100.pdf
Datums and PCF explained on page 48-49.
Hope that helps.
Andrew
FollowupID:
642169
Reply By: macbushy - Sunday, Jul 19, 2009 at 13:28
Sunday, Jul 19, 2009 at 13:28
Pedro,
I had a problem pegging points and it turned out to be people supplying me with 2 different formats of locaation.
The difference between Deg Min Sec and Degrees Decimal min. The variation in distance was similar from memory.
Check what format the co-ordinates are in.
AnswerID:
375174