GPS Marks Inconsistent

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    Posted: 17 Jan 2017 at 7:22am
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Might be a dumb question but here goes. When I sold my last boat we were running a lowrance gps unit with the broadband sounder. I took some of my treasured marks off the unit and kept them safe for the last 5 years. I have a Garmin unit on the new boat. I entered the marks and they seem to not be showing on the charts as I remember them and several are way off. Could it be due to different charts in the units? Or is there different setting options that could change their position slightly? Any help would be appreciated.
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Post Options Post Options   Likes (0) Likes(0)   Quote Grasshoppa Quote  Post ReplyReply Direct Link To This Post Posted: 17 Jan 2017 at 7:44am
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Bugga that would be pretty gutting
Wouldnt expect its the charts but possibly the format, especially if you wrote the down?
http://www.gps-coordinates.net/gps-coordinates-converter

I changed from a Lowrance to a Garmin a couple years ago, saved lowrance file to a MMC card, downloaded some recomended software from the net and converted marks to the Garmin files, everything bang on

https://www.google.co.nz/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=converting%20lowrance%20waypoints%20to%20garmin

Good luck
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Post Options Post Options   Likes (0) Likes(0)   Quote Steps Quote  Post ReplyReply Direct Link To This Post Posted: 17 Jan 2017 at 7:58am
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Check if the co ordinates are in the same format...
 ie deg mins sec  or deg mins decimals.
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Post Options Post Options   Likes (0) Likes(0)   Quote JustAnotherSpearo Quote  Post ReplyReply Direct Link To This Post Posted: 17 Jan 2017 at 8:40am
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I have a lowrance elite 7 and an elite 5 on the 12ft tinny. Have noticed that some of my cray spots have been way off, in particular I know of one rock that has been marked 3 times on the elite 7 unit and are a fair distance from where the rock actually is even though we anchor ontop of the rock and mark it that way. not sure if this helps but is what ive found. 
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Post Options Post Options   Likes (0) Likes(0)   Quote GSPOT Quote  Post ReplyReply Direct Link To This Post Posted: 17 Jan 2017 at 8:47am
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Biggear - PM me those marks and ill check them for you! Wink
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Post Options Post Options   Likes (0) Likes(0)   Quote Steps Quote  Post ReplyReply Direct Link To This Post Posted: 17 Jan 2017 at 9:08am
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What maps are you running in the lowrance... navionics or the Cmap?
 I run the navonics in the old huminbird on the tab and cell... everytime spot on.. within a couple meters at most
 The elite has Cmaps  (which came with it.. also runs navionics)  the are very basic.. so basic they are the same as the open source created maps from the linz data that one runs on openCPN software.
 I only use the elite for sounder not for accurate gps..
The open cpn on the tab And on home computer is way out and if going by the description above.. basically same issues/problem when copying marks from the navionics to the copied CMap maps.
 When I 1st started coping the marks over... thats when I did not reasled had the seconds/ decimal setting the same.
Corrected that and still had a issue.
It was convent as was doing all this side by side between the computer, tab , cell at the same time.

 I just use the open cpn to record trips/ routes catches etc.

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Post Options Post Options   Likes (0) Likes(0)   Quote waynorth Quote  Post ReplyReply Direct Link To This Post Posted: 17 Jan 2017 at 9:20am
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Check the datum being used on the Garmin. It should be WGS84, but after a similar problem with a friends new GPSMap we found it was set to NZGD49.

Another setting we had to change was the position format -  needed to be changed to Hdddmmm.mmm and not to "New Zealand".


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Post Options Post Options   Likes (0) Likes(0)   Quote Bay Marine Electronics Quote  Post ReplyReply Direct Link To This Post Posted: 17 Jan 2017 at 9:24am
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Check the Garmin is set to the correct position format. When you first boot them up it asks you what format you would like and one of the options is "New Zeland" and another is "New Zealand TM" - both of which are the topo map format.
The correct format for 99% of people is "DDD MM.MMM" which is Degrees, minutes and decimals of minutes.
The other one which you might have, or might have had on your lowrance is Degrees, minutes and seconds "DDD MM SS.S" Which would put you close to where the marks were but not accurate. This is more the old school way of describing location.

Home->Settings->Units->Position Format   

Also Home->Settings->Units->Map Datum

Map datum should be set to WGS84. But if it is incorrect the inconsistancy should be about the same for all waypoints.
0800 BAY MARINE www.baymarineelectronics.co.nz
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Post Options Post Options   Likes (0) Likes(0)   Quote biggear Quote  Post ReplyReply Direct Link To This Post Posted: 17 Jan 2017 at 10:51am
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Settings are all as you recommended. Perhaps a map upgrade is needed? Not adding up at present.
Dont let the grey hair fool you!
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Post Options Post Options   Likes (0) Likes(0)   Quote waynorth Quote  Post ReplyReply Direct Link To This Post Posted: 17 Jan 2017 at 11:42am
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biggear have you got a sample position from the Lowrance you could post ? A third position format sometimes used is dd.ddddd, with the minutes/seconds all converted to decimals of a degree. If you have saved them in one format, then try and read them in a different format, that could be your problem.

I did the same exercise transferring waypoints from Lowrance to Garmin. My HDS8 would only export in Lowrance's proprietary .usr format, & I had to use GPSBabel to convert them to the generic .gpx format so the Garmin would read them - did you do a similar exercise ? 
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Post Options Post Options   Likes (0) Likes(0)   Quote NZTurtle Quote  Post ReplyReply Direct Link To This Post Posted: 17 Jan 2017 at 1:14pm
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Does t6his mean you have  new boat Stu? If so, great news!
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Post Options Post Options   Likes (0) Likes(0)   Quote biggear Quote  Post ReplyReply Direct Link To This Post Posted: 17 Jan 2017 at 3:58pm
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Yep Dave. Got one back in October. First trip on Saturday to me old haunts and got zilched. But there was definitely something amiss with the marks.
Dont let the grey hair fool you!
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Post Options Post Options   Likes (0) Likes(0)   Quote biggear Quote  Post ReplyReply Direct Link To This Post Posted: 17 Jan 2017 at 3:59pm
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Originally posted by waynorth waynorth wrote:

biggear have you got a sample position from the Lowrance you could post ? A third position format sometimes used is dd.ddddd, with the minutes/seconds all converted to decimals of a degree. If you have saved them in one format, then try and read them in a different format, that could be your problem.

I did the same exercise transferring waypoints from Lowrance to Garmin. My HDS8 would only export in Lowrance's proprietary .usr format, & I had to use GPSBabel to convert them to the generic .gpx format so the Garmin would read them - did you do a similar exercise ? 


All I did was write them down before I sold the last boat and then re-enter them into the Garmin off my spreadsheet.
Dont let the grey hair fool you!
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Post Options Post Options   Likes (0) Likes(0)   Quote ofthesea Quote  Post ReplyReply Direct Link To This Post Posted: 17 Jan 2017 at 4:20pm
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Could one GPS be set to true north and the other set to magnetic north?
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Post Options Post Options   Likes (0) Likes(0)   Quote MikeAqua Quote  Post ReplyReply Direct Link To This Post Posted: 17 Jan 2017 at 4:27pm
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Do you remember what coordinate format and datum the old GPS was set to? 

It seems likely to me that a difference between the two units in coordinate format and/or datum is the source of the problems you are experiencing.
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