Waypoint Format Queries

[Splash]

HI Team,

I have read some previous posts by you guys on Waypoint compatibility with Datum use - and need your advice..

I have a Garmin GPS 292 unit with WGS 84 as datum.

For some reason, all of my waypoints on this unit are in UTM/UTS format.

How does this position format differ to hddd mm. mmm?

What issues arise (if any) when I use the UTM format with WGS84 Datum?

How can I convert the format of these waypoints back to "hddd mm.mmm format"?

What position format should I have my coordinates in to suit the WGS 84 datum format?

Also, should I use "True North Heading" or "AUTO Mag Var Heading"?

Splash

[deadbeatloser]

go into your settings and you should be able to bring up set up menu from there make your changes , with heading its up to yourself as to which way you prefer

[Splash]

I can go into the settings in the unit and select a different position format.

If i do this, may the points be adversely affected in way of distorting the figures (somehow)?

I read elsewher eon this forum - that the wgs84 datum needs to have the hddmm.mmm postion format to eleimiante inaccuracies - is this correct?

And, explain the differences between the different formats of "HEADING" - true vs Mag Var.

Splash

[fsh00]

Heading TRUE is the true north/south headings to the poles of earth, magnetic is the heading north/ south with the magnetic variation applied wich varies depending on the position of you point on earth, true north is allways used on charts and the variation is applied to it depending on the degree of variation at that point,You should use true north working from charts to gps and if you are going to steer by compass you should apply the variation to your compass for a true heading.
Pete.

[fsh00]

Wgs84 & dmm.mmm is the common 4 working on most newer marine charts and positions can be directly input into gps if using this datum, older charts that used aus66 i think it was had to have the positions moved to agree with wgs84 eg( position must be moved 0.03N & 0.05W to agree with this chart),when you get your positions from other sources allways find out what datum they used and position format then change your gps to these settings, enter them then change back to wgs84 & ddmm.mmm and it will automaticly change them 4 you.

[fsh00]

True:true heading
Variation:magnetic variation at location
Magnetic: compass heading with variation applied(marine compass not gps)
deviation: any thing that interferers with compass heading EG: metal,electronics,ect.
compass:course to steer from compass.

true:360deg OR 000deg
variaton:3deg west add to 000deg = 003deg
magnetic heading:003deg
deviation:2deg east,error from electronics ect,subtract from 003=001deg
compass: course to steer = 001deg

True=True
virgins=variation
make=magnetic
dull=deviation
company=compass

[Splash]

Thank you chaps

[krillx]

I read elsewher eon this forum - that the wgs84 datum needs to have the hddmm.mmm postion format to eleimiante inaccuracies - is this correct?

The numerical format of the coordinate has no fixed link with the datum (elliptical model of the earth used to map the coords onto). You could represent a wgs84 datum coord in hddmm.mmm or hh dd mm ss or hh dd mm ss.s numerical format. A hh dd mm.mmm format coord will be a little more accurate than a hh dd mm.mm or hh dd mm ss coord because of the one additional significant figure but I think in practice the diff will be negligible.


If you need to convert between any numerical formats (not datums) there is a handy converter at http://maps.bonzle.com . Just dump your coord in the search box and it will give you a page showing all the different numerical formats.

[FNQCairns]

One thing to remember and hard won by me is, if you do not enter the new coordinate in while your unit is using the exact same datum the coordinate was produced from, then all sorts of variance happens.

My rule now is if I am not told or cannot see (trust) which datum was used then I just don't bother entering it, not worth the effort. Like some of the net coordinates and book coordinates around the traps.

cheers fnq