Magellan Sportrak setup for NZ Map Grid coordinates

[bread]

Hi all

Magellan GPS units dfon't have the NZMG datum in the units like some Garmins so I have to use the 'user grid' that is avialable. The data I got from Electronic Navigation Limited (NZ suppliers)was used but when checking the coordinates on a topo map it puts me 200-300 metres out of position. I am aware there is some error due to the rotation of the lat/lon meridians compared to the NZMG but would expect to get better accuracy than this. Before I send this unit back and buy a Garmin I would appreciate if anybody could offer assistance on the following.

1/ Who knows how to set up the magellan to get some better accuracy.

2/ How accurate are the Garmin units using the NZMG and topo maps?

3/ Which Garmin offers the best service for tramping (bush) work?

 

Thanks for your help.

Cheers

Bread

[+BaldEd]

I don't anything about Magellans, except that I was tempted a couple of years back to get a 315. After reading how good the GARMIN 12XL was under tree cover I bought one of those instead. Glad I did. It has NZMG and integrates very well with Polymedia's NZMapped for GPS. I only have the SI topomap CD's and am very happy with what I have.

[bread]

Hi BaldEd

Thanks for the info. The 12XL may be worth pursuing. I am interested in how accurate it is. When I install a waypoint using lat/long I get a different MZMG reference to that when I convert a lat/long corodinate to NZMG using the LINZ converter calculator. What sort of error do you get using your Garmin?

Cheers

Bread

[+rediguana]

quote:

---

Originally posted by bread:

... but when checking the coordinates on a topo map it puts me 200-300 metres out of position

---

 

Hi Bread.

 

I know that to achieve the sort of translation you are talking about, on my 12XL I would have to enter the coordinates with the GPS set on LatLong/WGS84. Then you change the setup to NZMG/NZGD49 and the coordinates will be bang on. I assume for your Meridian you will need to enter in LatLong/WGS84, and then convert to your user grid.

 

Another way would be to use software to translate from one projection to another.

 

In the medium term, the best solution is going to be having the new topo maps come out under the NZGD2000 datum. This mirrors WGS-84 to within about 10cm

 

Cheers Gav

[evilC]

Didn't spot this thread until too late, so have a look at my last post to:

 

eTrex automatic datum selection for NZMG display selection

[bread]

Hi to you all (again)

 

I think I've got it licked!! i have changed the false Northings and Eastings to include the error I was getting and it seems to have worked. I have tested it on a number of survey points obtained from the LINZ website. These points have very accurate Lat/Lon and NZMG coordinates. Fed the NZMG coordinates into my GPS and got very close lat/lon projections. I will now load in some known sites around Auckland /Papakura area and see if I can find them.

 

Thanks for all your help. See you all on the playing field

 

Cheers

Brian

[bread]

Grrrrrr. I have been using a number of survey marks as reference points when checking out the Magellan setup. Tried all ways but when visiting the actual reference point I am still 100s of metres off. I even used a survey mark coordinates to set up the GPS then went walkabout. At that mark it put me within 3 metres of the mark. Then visited 3 other marks at about 6km and 10km distance the GPS put me 200 and 250 metres from the mark!!! I GIVE UP. TODAY I AM RETURNING THE MAGELLAN AND BUYING A GARMIN GPS72!! So there!

[da_snoop]

[+ags]

I've probably come into this conversation too late - but you need to look at this page:

 

http://www.ualberta.ca/~norris/gps/nz/NZ2.html

 

and this page

 

http://www.ualberta.ca/~norris/gps/nz/NZ.html

 

I used to have an early GPS12 that didn't support NZMG. The stuff above worked O.K., but it was an approximation and the results were disappointing even for tramping.

 

As far as I know, the newer Garmin's do the full calculation for NZMG and are as accurate as the satellite readings. I've checked my newer GPS12 (with NZMG) against a few local survey marks and got 5 - 10 m accuracy. I guess this is the limit of the machine, rather than calculation error.

[bread]

Hi ags

Thanks for the web site. I have already got that info. I returned the Magellan Sportrak and am now the owner of a Garmin GPS72 I have taken a waypoint mark directly over one survey mark and the NZMG reference was within a few metres!! Maybe success at last I have loaded a number of other survey marks to test before I am fully convinced and have enough confidence in the GPS to go bush. Obviously with map and compass as a back up. I have completed one track course and done the tracback which worked our really good. So far so good.

 

Cheers

Brian