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View Full Version : Garmin Dakota 20 - Tracback & Where To? advice required



anton8
11th September 2010, 03:04 PM
Hello there. I've just signed up.

In my work ( archaeology/photography) I sometimes use a little Geko 101 I bought second-hand years ago. I sort-of know how to use it!

Anyway, a friend has just retired and has bought a super-dooper metal detector and a Garmin Dakota 40. Because I mentioned that I sometimes use a GPS I became, in his eyes, an expert. Er, I'm not.

I've read the manual and the unit sort of delivers what he wants it to do. Could someone spare a minute or two on the basic operation of this unit? Thanks in advance.

First, it might help if I outline what he wants it to do. He wants to park the vehicle and head off into the scrub with the metal detector and then retrace his steps using the unit's compass to point the way. He's a bit concerned about getting lost.

He wants me to set it up - and away he goes! What mode do I need?

Seems to me this unit is capable of all sort of wonderful things, but all Bill wants is a simple, accurate homing device.

Cheers. Tone.

Michael
11th September 2010, 03:52 PM
Welcome Tone
Do not have a Dakota, so I cannot tell you any more than the manual.
Any modern Garmin will do what you want straight out of the box.
Just check on the 'tracks' page that 'track record' is switched on.

then retrace his steps using the unit's compass to point the way. He's a bit concerned about getting lost.
Following a compass course from point B back to point A only works at sea, or in fairly flat open country.
Any cliffs, creeks, gullies, thick scrub can make straight line courses hard to follow.

But as long as he has recorded his track, he can view it on the 'map' page & follow it exactly, (or cut the odd corner) back to his car.
Also a good idea to always mark a waypoint before he leaves the car.

anton8
11th September 2010, 04:39 PM
Thanks for that, Michael. Very helpful. I'll set it up as you suggest and give it a whirl around the block.

The little Geko I own works as you describe and I'm sure the Dakota can do the same.

Cheers. Tone.

Wahroonga Farm
11th September 2010, 05:05 PM
Yup.

Keep it simple

But it can confuse (http://www.gpsaustralia.net/forums/showthread.php?t=12947). :)

The Explorer
11th September 2010, 07:16 PM
Hi
Tracback is one way, but if, for example you walk 5km all over the place but are only 1km from camp, why walk 5km to get back. My suggestion would be to mark a waypoint at camp and then go to the waypoint manager and set GO to this point. At any time you can then navigate back to camp using the GPS (assuming you leave the GPS on, other wise turn it on and then set GO).

Practice in a safe environment before heading bush. Until you get confident in using a GPS and understand its limitations (eg battery life) and yours, I would not rely on one GPS alone (eg maybe have normal compass, topo map or always confirm location relative to camp with landmarks (some will suggest never rely on GPS alone). UHF radios are another good safety measure.

Cheers
Greg

Smouch
11th September 2010, 10:14 PM
bought a super-dooper metal detector and a Garmin Dakota 40

Do you mean a Dakota 20?
The 3D compass is excellent in this unit... I would follow 'The Explorers' suggestion of marking a waypoint at camp and then press 'where to'-'waypoint'-select the camp sites 'waypoint' and whenever you go to the compass page it will point back to camp. also in the setup page under 'tracks' ensure that the 'track log' is set to 'record + show on map'.

anton8
12th September 2010, 07:36 AM
Thanks all for the tips.

Smouch: Er, yes, it's a Dakota 20, not 40. Me dill.

Also, safety advice received and understood. I had decided to advise Bill NOT to rely on the unit and to have back-up systems in place.

This damn thing is giving me the irits! If it were mine I'd chuck it in the Campaspe River let the carp work it out. I'm obviously doing something wrong. With the Geko, I can mark Home, wander around, hit Go To, follow the arrow and - bingo - Home!

The Dakota won't play that game. The "Track" it creates bears no relationship to what I know is the correct route. It points me in the opposite direction, which is not entirely satisfactory. Still, will persevere.

Does anyone here have this particular unit and, if so, could you spare a few minutes to walk me through the set-up procedure?

Consider me ignorant, indeed thick, regarding GPS. If you want info on cameras, photography - I'm your man!

Cheers. Tone.

Avtrician
12th September 2010, 08:24 AM
Perhaps the Dakota is trying to follow a road, can you set the travel mode to off road

The Explorer
12th September 2010, 08:39 AM
Perhaps the Dakota is trying to follow a road, can you set the travel mode to off road

Or maybe its set to track up (instead of north up)...or something - that can get confusing sometimes if you are not use to it.

Cheers
Greg

Wahroonga Farm
12th September 2010, 09:31 AM
Here's some Oregon happy snaps.

Set a Waypoint, named it Home, went for a wander.

Using 'Where To?' a Waypoint and the 'Compass' feature to direct me ... I found myself again home in no time. :)

I'm sure the Dakota is identical.

anton8
12th September 2010, 09:50 AM
Ah, thanks, chaps. I will set to North Up. Also, will set to Off
Road. More experimentation. The carp can wait.

Also, Bill is happy for me to get this thing working, no matter how long it takes. I certainly won't return it until I am satisfied that it will do the job, reliably and accurately.

Again, thanks for the help. Er, I'll probably be back ... but much to go on with for the present.

Camera tip: I use Nikon SLRs in my work - digital and film - but am always on the lookout for a decent compact. Samsung of all people have just come out with a nice little unit, the EX1. It's well-priced, strong, and the image quality is said to be excellent. It also shoots RAW format, the preferred mode for pros.

Cheers. Tone.

Wahroonga Farm
12th September 2010, 10:00 AM
I find 'Track Up' works for me ... ie works well if you are walking in a straight'ish line.

But have a play with both options, once you have it sorted.

So how about the 'Tracback' function?

Go to Track Manager, Current Track, View Track, hit Tracback arrow and away we go again.

At this point it is worthwhile understanding how Tracback works and and touch on a brief discussion on GPS 'tracks' and 'routes'.


What is the difference between ROUTES and TRACKS on my GPS?

Tracks are made up of data gathered automatically from your motion while the GPS is turned ON. They provide a record of where you've been, and when, so you can later determine your path, time, height and speed. There may be hundreds or thousands of such points in a track. They don't have names and you can't easily get the location of any particular one.

So a track records full details of the path you have travelled. It is often called a breadcrumb trail, as in Hansel and Gretel.

Routes are generally made up of a series of significant points along your planned path. The GPS will tell you the bearing and distance to the next point in sequence as you navigate along your route. Each point may be named. In fact, a route is really just a sequence of waypoints. There may only be a few tens of points in a route or many hundred. As Garmin GPS have evolved, the number of points in a route and the number of routes that may be stored has increased significantly.

So routes provide a path with directions to where you are going.

If you use Garmin's TracBack function, it will turn a track into a route that goes in the opposite direction. This is done by a_nalysing the path of the track and automatically creating waypoints at significant turning points in the path.

Thanks to Dave Martindale (http://gpsinformation.net/main/tracklog.htm) (I have updated his excellent information) Using Tracback it is important that you teach Bill a bit about current track and saving and clearing tracks ... to avoid confusion with Tracback.

Where To a Waypoint is simple.

5.1km ... brisk walking. :)

Wahroonga Farm
12th September 2010, 04:51 PM
Camera tip: I use Nikon SLRs in my work - digital and film - but am always on the lookout for a decent compact. Samsung of all people have just come out with a nice little unit, the EX1. It's well-priced, strong, and the image quality is said to be excellent. It also shoots RAW format, the preferred mode for pros.

Cheers. Tone.Thanks :hatoff

But no HD video on the EX1. ;)

But now you'll need a camera with geo-referencing. :)

Michael
12th September 2010, 09:18 PM
I prefer to use 'North Up' easir to relate it to my paper maps.

In spite of/because of all the other replies I repeat from my post 2 of this thread:

Following a compass course from point B back to point A only works at sea, or in fairly flat open country.
Any cliffs, creeks, gullies, thick scrub can make straight line courses hard to follow.

But as long as he has recorded his track, he can view it on the 'map' page & follow it exactly, (or cut the odd corner) back to his car.
Also a good idea to always mark a waypoint before he leaves the car.

anton8
13th September 2010, 05:13 PM
"No HD video on the EX1"

Jeez, some people are never satisfied. All right, check out the new Nikon P7000. See PHOTOGRAPHYblog or DCreview. To my lights, this is a real goer. A potential photographic back-up workhorse. Strong, too. TIP: Wait a few months. New cameras always have firmware bugs. TIP: In harsh conditions, always carry a camera with an optical - not electronic - viewfinder.

+++

Bill's GPS: I have set it up as per suggestions here and given it a run in the various modes - thanks! - and it does work - to a degree. But, seriously, I'm beginning to reach the conclusion that the unit is too complicated for Bill's purposes. Too many variables. Overly complicated. I often work on building sites during the course of my work. Health and safety is always an issue. My rule is: Keep it simple. Keep it safe.

To reiterate: I will not hand this unit back to Bill until I'm satisfied. Anyway, I was in a Bendigo camera shop today and saw a Bushnell Backtrack GPS unit. A simple device that, as I understand it, does one thing and that thing well. I will persevere with the Dakota 20, but I am contemplating suggesting to Bill that he forget the Dakota - maybe place it among the carp in the Campaspe - and buy a couple of Backtrack units.

Any thoughts?

Cheers. Tone.

Nicko
13th September 2010, 06:30 PM
we have the backtrack in stock $119

Smouch
13th September 2010, 10:35 PM
A simple device that, as I understand it, does one thing and that thing well.

The 1 thing that the Backtrack does.... is done better in the Dakota.
The compass must be held flat unlike the Dakota, the arrow is only +/- 20degree ticks + slow to update/keeps turning off... unlike the Dakotas fast 1 degree resolution and you can press 1 button to mark a waypoint in the Dakota too without even talking about its on-board map if needed. To chuck a Dakota in the creek over a Backtrack is ridiculous. If it comes to that... chuck the Dakota my way any time.

anton8
13th September 2010, 11:39 PM
Smouch.

Er, hello? That was what's called an ironic joke. I have, literally, no intention of feeding carp in the Campaspe River with a brand new Garmin Dakota 20 GPS. To spell it out. That was a weak joke. INSERT GRIN HERE. Also, the carp would probably not appreciate the technology, therefore wasted on 'em'. However, not sure about that ...

I have asked some serious questions here and have received serious, helpful replies. Again, thanks.

However, I have now learned a lesson on this forum. Do not joke. Sorry.

Smouch
14th September 2010, 12:35 AM
there are plenty of people goofing off all the time round these parts. I was just trying to stop you taking a large backward step. With out looking at peoples faces its hard to tell the serious ones from the tongue in cheek. Keep persisting with the Dakota and you'll be all-right :hot: My wife keeps reminding me to grow a humorous bone someday....

Nicko
14th September 2010, 12:36 AM
you can joke, you just need to use the smileys so that the serious breed understand that it is a joke. :hysterica :welcome :wave

anton8
14th September 2010, 01:10 AM
:wave

anton8
14th September 2010, 01:32 AM
Right. Bugger this. From now on in ... hit Non Joke Mode/Country and Western Nose Music/Utes/Sheep/Utes/ Orange, NSW/ Fat genes/utes
... political dills ...

THAT was a joke!

+++

I suspect it fell a bit flat.

+++

GPS: What I'm suggesting for Bill is a Backtrack unit. Then, at least, he will be on his way. The knowledge and operation of the Dakota can come later.

Cheers. Tone.

anton8
14th September 2010, 01:33 AM
nicko

The "serious breed"?

That is very funny.

Michael
14th September 2010, 06:11 AM
GPS: What I'm suggesting for Bill is a Backtrack unit. Then, at least, he will be on his way. The knowledge and operation of the Dakota can come later.
You know Bill & we don't, so you are probably on the right track (bad pun intended) :hysterica
Although GPS features/menus etc can be a steep learning curve, I find most people climb that hill after a little while.
They then wish they had bought the fancier unit with more features, maps, functions etc.
So they end up going out & spending more money.
A last thought, if Bill has teenage boys, they will figure it out in 15 minutes & be able to tell him how it all works.
Happened to a mate of mine who is a keen bushwalker, but a total ludite, he thought my GPS looked great, so bought one the day before he & the boys left for Tassie & a walk round the Western Arthurs. The boys used the GPS, he was befuddled.

Wahroonga Farm
14th September 2010, 07:38 AM
Yes.

I do agree that using a fairly complex mapping GPS seems rather overkill for a simple homing task.

A Garmin handbook has never been an intuitive read. :)

Michaels salient warnings about crashing 'willy nilly' through the bush on a blind compass course for home; does need a careful understanding of the type of country and the users capability when using a GoTo type of function.

In alpine regions (and many others I can think of), a simple GoTo compass course in white out or low visibility conditions could clearly be dangerous; leading you into an impassable cliff or chasm.

With the attendant disorientation and rising panic a fatality is clearly possible, despite the 'best plans' and intent.

------------

So here is my attempt at demystifying GPS based compass 'Go To' a waypoint functionality.

Let me state up front that for the task of 'Go To' a waypoint, the Dakota 20 will be the vastly superior device in practice due to its 3-axis (gimballed) electronic compass, as Smouch has already advised.

http://www.gpsinformation.org/penrod/dakota/compass.jpg

For Garmin GPS, the magnetic electronic compass only activates when you slow down under 3 mph. If you are going faster than 3 mph, it relies on the GPS generated heading for the compass arrow.

I do not know when and how the Bushnell uses movement to determine compass direction. It certainly uses its internal electronic magnetic compass when held stationary.

How a GPS electronic compass works

1. The GPS internal magnetic compass MUST be calibrated for your present location.

What is calibration and why is it necessary?

Calibration is necessary due to the variation in the magnetic field (http://www.ga.gov.au/geomag/) over the earth's surface, leading to a variation between true north and magnetic north dependant on your global location. The earth's magnetic fields are slowly moving as the magnetic flux patterns of the earth change. For example in Eastern Australia (-32, 151) between 1985 (11.653E) and 1995 (11.963E), the magnetic deviation (or declination) moved 0.3 degrees.

http://img688.imageshack.us/img688/4442/magneticdeviationaus.gif

The map shows that the magnetic variation for Australia varies between 5 degrees west in Perth, to around 15 degrees east, down in Hobart. When you move to an area with a different magnetic variation, or change batteries, re-calibration will be required.

For the Bushnell, calibration is achieved by holding the compass level and moving it in a figure 8 pattern in front of your body as shown in the following diagram. The internal magnetic compass is a 2-axis device (NOT gimballed), so if it's not held absolutely level, it'll give you bogus directions.

http://img688.imageshack.us/img688/4351/bushnellcompasscalibrat.jpg

For a Garmin hand-held, calibration involves holding the GPS in front and level and rotating your whole body twice.

http://img820.imageshack.us/img820/5492/compasscal.jpg

During the calibration procedure it is important that you:


Ensure that you have good GPS acquisition.
Are not near metal bodies or overhead power lines that may deflect the magnetic compass.


All GPS with an inbuilt magnetic compass require similar calibration. Garmin hand-held GPS also provide for direct magnetic variation input via the User screen, to Manually set the magnetic variation value.

2. Mark your 'Home' (waypoint). This is recorded as GPS coordinates by the device. The internal magnetic compass takes no part in recording the 'home' position.

3. Turn it off and head off on your trip.

When suitably lost :), turn it on again, wait for it to acquire GPS location and hold it level.

4. The Bushnell then computes the true GPS bearing and distance from your 'current' GPS location, to the 'home' GPS location.

5. Now this is where the 'smarts' kick in.

Let's assume that 'home' is due west of your current location (270 degrees) as calculated by the two GPS coordinates. After the calibration process, the GPS has determined and stored the magnetic variation for this location.

By way of example, let's assume that the the magnetic variation has been calculated to be 10 degrees east of North during the calibration procedure.

The device incorporates the 10 degree magnetic error and electronically indicates due west no matter the orientation of the GPS.

Does that lot that make any sense? :)

-----------------

So perhaps one more question ... have you calibrated the Dakota compass?

Without calibration; performance whilst stationary will be erratic. :)

Wahroonga Farm
14th September 2010, 07:54 AM
Right. Bugger this. From now on in ... hit Non Joke Mode/ Country and Western Nose Music/ Utes/ Sheep/ Utes/ Orange, NSW/ Fat genes/ utes ... political dills ...Where's that button?

:hysterica

Wahroonga Farm
14th September 2010, 08:12 AM
I may be preaching to the converted, but the best learning always happens when the student is truly engaged and inspired by the teacher and topic.

------------

So maybe conduct this training session ... in reverse.

Rather than returning for that cold beer at the end of a days prospecting, make it a 'treasure hunt'.

Go bury a big treasure, set the coords and let Bill find it using the GPS.

The lights may come on ... :)

anton8
19th September 2010, 08:36 AM
All sweet! And many thanks to all those who provided a course for me to plot in nutting out this unit. (Pun intended.) Most appreciated. My apology for not responding, but had to whip out to discover the Source of the Nile.

Went for a few test runs with Bill the other day. Found that Trackback on the Dakota was the most accurate, at least in the vehicle. Go To went haywire in the vehicle, a large 4WD. Something to do with interference from the vehicle's electronics, methinks?

Yes, Michael, as one gets older, the old brain cell sometimes has difficulty resolving some concepts. I've found, however, if one is aware of this, it's not a problem that can't be overcome. I'm a stubborn little bugger and don't like to be beaten. Also, it's very satisfying when the penny finally drops.

Bill is now considering the Bushnell device - for his wife so she won't get lost when they're both out in the scrub.

So, all up, a good outcome. Again, my thanks for the assistance!

Wahroonga Farm
19th September 2010, 08:53 AM
Good news. :swim
'Go To' went haywire in the vehicle, a large 4WD.

Something to do with interference from the vehicle's electronics, methinks? ...Was that only when stationary?
For Garmin GPS, the magnetic electronic compass only activates when you slow down under 3 mph.

If you are going faster than 3 mph, it relies on the GPS generated heading for the compass arrow.If so ... the magnetic compass is trying to do it's thing, which it won't in a vehicle.

You can turn the magnetic electronic compass off, if only used in the vehicle.

anton8
19th September 2010, 09:08 AM
Yes, John, when stationary.

General observation: This appears to be a friendly and informative forum!

Michael
19th September 2010, 08:05 PM
had to whip out to discover the Source of the Nile.
I thought Sir Richard Burton did that in the 1800s.