Lets talk GPS

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Lets talk GPS

Post by Bignuggs on Sat 02 Mar 2013, 5:43 pm

This is in the wrong section but I'll move it later. I'm no expert with a GPS coz I never use the sod of a thing.
To answer a question that has been put to me, "How do you record a location in Metric" and not Lats & Longs.
I'm no expert with a GPS but I have looked at my Oregan 550 and I can change how it reads. I think it means, if I mark a waypoint, it will show in metric. I think that's what it has done coz that is what it is showing. It's not showing Lats & Longs.
I've probably just answered my own question but if someone asks for metric readings, can I trust the GPS ?

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Re: Lets talk GPS

Post by Guest on Sat 02 Mar 2013, 5:45 pm

great mate --u have already confussed me and i havent got one--

regards
oneday

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Re: Lets talk GPS

Post by Bignuggs on Sat 02 Mar 2013, 6:20 pm

Sorry if I have confused people.
If I change how my GPS reads (metric), if I mark a waypoint, it shows as metric readings. My question is, can metric coords be trusted compared to lats and longs ?
Personally, I think it should be trusted. It was just a change of how it is reading but I would like some expert advice.

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Re: Lets talk GPS

Post by toad on Sat 02 Mar 2013, 6:49 pm

I use UTM as I find that easiest.
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Lets talk GPS

Post by albo on Sat 02 Mar 2013, 7:12 pm

me to Toad UTM , 1-100 maps , almost pinpoint precision, but then if you get a coord off someone you have to check the other guys settings true north , mag north , a few hundred metres in it.
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Re: Lets talk GPS

Post by Bignuggs on Sat 02 Mar 2013, 7:18 pm

I've got it set as "UTM UPS" whatever that means and the other settings are "WGS84".
As a test, I wrote down the metric readings for where I am, checked it against google earth and bugger me, it's not far off the mark.
So I think I've answered my own question. Set your GPS for metric and take the readings. Or am I wrong ?

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Re: Lets talk GPS

Post by Bignuggs on Sat 02 Mar 2013, 7:23 pm

do you have it set for "True or Magnetic" North ?

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Re: Lets talk GPS

Post by albo on Sat 02 Mar 2013, 7:41 pm

Hi Cliff , the usual geo settings are true north, not sure why the magnetic option is there , probly a surveyor like Darwin Dave on finders could give an explanation . If you were pegging ground it would be very important , id reckon the caterpiller could have some info also, but cliff true north is the setting .cheers albo.
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Re: Lets talk GPS

Post by Bignuggs on Sat 02 Mar 2013, 7:50 pm

Hi Albo,

Thanks for the info, just checked my GPS again, I do have it set for "True" north, so all's good there. The 550 does give you the option to switch it between "True and Magnetic North".

Now here's a difficult question, do all GPS units have the capacity to switch options between "Metric/Lats & Longs and Magnetic & True North". I've only stayed with garmin coz the new units give better options to switch to what you want. Working the mongrel out is another thing.

Cheers
Cliff

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Lets talk GPS

Post by albo on Sat 02 Mar 2013, 8:36 pm

Cliff , iv had 4 gps since they came out , the first was a brick type lowrance which had the north /true option , 3 garmins after that , main failure with all of them was user damage , on the dash in the sun too long , leave it on the mudguard & forget & take a drive over the next hill etc lol! which brings me to the next precaution , after each trip store your 1 nugget or patch finds in a little black book after each trip so when the gps shts the tin alls good. Learned that the hard way , all my wanders in Halls ck , few bits here & there died with my lowrance 10 years ago. As far as brands go , its a bit like ford / holden, but in the gps world its magelan or garmin in my circle of friends. Not up with the latest but my mate had a magellan , me with a garmin , both good but the magellan took a long time to hook on to sats some days , any how the fingers have got asthma after that lot ,albo.
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Re: Lets talk GPS

Post by Bignuggs on Sat 02 Mar 2013, 10:23 pm

Buggered if I know why a got a new one, I hate them but I do luv new toys Razz
I've never had to use one yet to find my way home or back to camp and sure as hell I ain't marking waypoints for finding horse shoes

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Re: Lets talk GPS

Post by boobook on Sun 03 Mar 2013, 5:58 am

After falling out with my old Magellan I agree with Albo, write your co ords into that little black book.
Yep, also the time the Magellan took to establish the sats, bought a Garmin Rino which is bloody near instant in setting up and the UHF built in is a cracker. In the hills out back of Burtville well over a km. on the 1/2w. setting (5w. max)
Back to the topic, very easy to change and save settings to suit whatever master map it is being compared to. I prefer the metric scale, have historical mines set onto Google earth which shows their co ords in metric and pretty accurate too.
mike
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Re: Lets talk GPS

Post by Guest on Sun 03 Mar 2013, 9:51 am

albo wrote: me to Toad UTM , 1-100 maps , almost pinpoint precision, but then if you get a coord off someone you have to check the other guys settings true north , mag north , a few hundred metres in it.

"mag north" or "true north" makes no difference unless you're trying to use the GPS in conjunction with a compass. The GPS is a stand alone nav device and will always tell you where you are and where you should be going to reach your target, irregardless of "true" or "mag"" North. If the GPS is set up to match the map that you're using at the time it will be accurate to THAT MAP ONLY (or any map that was drawn/made with the same datum - also known as cartography. Use another type of map or take a reading off yer mate's GPS that isn't set correctly and you can be kms out!!

If anyone would like I can give you a rundown on Lat/Lon, UTM, Map Grids, Map Datums etc and how it all stiches together - including how it all fits with Tengraph. Any takers? It won't be just one "reply' either - it's a big subject.

WGS 84, GDA 84, AGD 84, UTM, Lat/Lon etc,etc,etc and how people constantly stuff up with Lat/Lon settings. When that happens, people get lost real easy and one guy nearly got his head ripped off because of precisely that!

Cat

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Lets talk GPS

Post by albo on Sun 03 Mar 2013, 8:59 pm

Hi Cat good info mate & appreciate that one , so the standard settings are true north ,wgs 84 & utm if you work it that way on your maps for 1- 100,000 , if not using the 1-250,000 maps ,deg .mins . sec is better for that one, thats how iv found it , cheers ,albo.
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Re: Lets talk GPS

Post by Guest on Mon 04 Mar 2013, 7:48 am

albo wrote:Hi Cat good info mate & appreciate that one , so the standard settings are true north ,wgs 84 & utm if you work it that way on your maps for 1- 100,000 , if not using the 1-250,000 maps ,deg .mins . sec is better for that one, thats how iv found it , cheers ,albo.

Albo, there aren't really any "standard settings" as you need to be careful that your GPS is set to what you're doing at the time. Which is why I and most regular users of GPS use UTM for everything these days. It rules out at least one other potential error - see the message below. But those settings that you've quoted above are about right as "general use". If it was me, I'd stick to UTM on ALL maps and get very familiar with one type of settings. Once you master UTM it's far easier than Lat/Lon. I haven't used Lat/Lon for years.

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Re: Lets talk GPS

Post by Guest on Mon 04 Mar 2013, 7:51 am

I’ll assume we all know how Latitude and Longitude works for a starting point.

The most common cause of error with Latitude and Longitude on a GPS is the way in which the read out is displayed. The display can be set to “Degrees, minutes and seconds” (DDD.MMM.SSS) or “Degrees, minutes and TENTHS of a minute” (DDD.MMM.mm) That’s a massive error if people don’t read it correctly.

In the south east of WA, say the Goldfeilds, one second of latitude is equal to about 100 feet or about 31 meters. Now, there’s 60 seconds in one minute of latitude. So each minute of latitude is a distance of 60 times 31 mtrs which equals: 1860 mtrs.
But if you have your GPS set on “DDD.MMM.SSS” which is as above and you take a reading off your mate’s GPS and his is set up on “DDD.MMM.mm”. Then the third digit readout on his GPS (“mm”) is not gonna be the same as your readout on your GPS in which the third digit readout is set on “SSS”.

A tenth of a “minute” is SIX seconds which is a distance of “6 times 31 mtrs = 186 mtrs”. But if the readout is in DDD.MMM.SSS then that last figure, even you’ve taken it off your mate’s GPS and punched it in yours may well be the number “one”. But it’s in “seconds” and not tenths of a minute! So “one” second is only 31 mtrs. So you’re adrift by about 150 mtrs.

Example: one GPS screen reads 31 degrees, 24 minutes, 1 second or “31 24 1”. It’s read out is set in DDD.MMM.SSS

The other GPS screen reads 31 degrees, 24 minutes, 1 or “31 24 1”. But this one is set on DDD.MMM.mm – tenths of a minute.

When walking across a mining lease boundary or looking for a target in heavy scrub etc – that’s a big error.

Now, to make the practical point of it all, a story. I met a guy in Leonora Caravan Park who was with his wife and mother-in-law on a prospecting trip. They were looking very upset and angry. I got chatting with them and they told me that they did all the right things – had permission from the local mining company to camp and detect on their leases. OK – no problem it seems. But they’d only been there a day when a local private leaseholder, known to be nasty piece of work when confronted with trespassers, came bellowing out the bush, screaming and ranting at them. It was so bad that his wife ended up in Leonora Hospital with a back strain as she tried valiantly to pack stuff up in the van and get away. Her husband was away in the scrub bippin’, so she was on her own. When he came back to camp, he copped an earful as well!! Now they couldn’t figure out how they managed to be on this guy’s lease when they’d taken a reading for the tenement boundary edge from a Tengraph map, punched that reading into their own GPS and yet still managed to be about 100 odd mtrs into this guy’s tenement. I had a look at the GPS and sure enough it was set up in “DDD.MMM.mm” or “tenths of a minute”. The reading from the Tengraph map was “DDD.MMM.SSS”. Disaster! And this guy is well known around Leonora for giving prospectors a very hard time if he catches ‘em. Imagine if it was you or you were looking for an old patch years later, after it was all overgrown or your mate has given you some co-ords for a patch that he’s finished with! Drove all the way from NSW to Sandstone only to miss the patch by 100 metres – sick eh! But it happens all the time and I’ve had people come to my place and ask me how they could get it so wrong.
I use UTM and have done for many years. It’s easier to use, it’s not subject to calculation errors as in the above tale and an increasing number of maps and service providers do it in UTM.

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Re: Lets talk GPS

Post by Guest on Mon 04 Mar 2013, 8:19 am

so after all that valuable info CAT--I need to buy a new gps can u recomend any breed in particular or buy any one so long as it isn't complicated to use..

regards
oneday

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Re: Lets talk GPS

Post by Guest on Mon 04 Mar 2013, 8:45 am

Ray,

In terms of the "set-up" of a GPS, they're all the same. It's often just a matter of having a test run in the shop ( I do this all the time) and seeing how easy/hard it is to alter settings - how many key strokes, can I see the text, how big is the text, what info is on any screen that I might have to use. I find some of the fancy coloured screens a PIA to use - too cluttered. Often the text is too small for my old eyes to see, especially if I'm driving in the scrub. As you say, "I'd buy any model as long as it's easy to use - FOR WHAT YOU WANT TO USE IT FOR" - different strokes for different folks. e.g I need something that connects to a laptop easily and gives me "moving map" without too much messing around. (Moving map -when a GPS talks to a laptop is brilliant, but it can be fiddly to get set up right). Others may not need this but they might like fancy stuff like having a built in short range UHF radio or a camera. I don't need either. I'm a believer that things should do what I bought 'em for and I don't buy things that "sound great" but in the feild they're a waste of time and money and just get in the way of a good GPS. e.g. my mate has Garmin that takes excellent photos and it's real handy when he's pegging leases for me as I get a picture of the papers on the peg and the GPS location and time at which the pic was taken. All good when I'm in Perth and he's in the bush - but his fancy GPS takes forever to get a fix and is hopeless at updating when driving, it's miles behind! When I'm in the bush, I have a Nikon camera and a watch,,,,,,,,,,,,,,so why do I need another "fancy do-dad" of a GPS when a basic one will do.

I nearly ditched the wife’s 15 year old Magellan last year as the LCD was starting to drop out screen pixels. I had a try of a whole load of GPS and the one that came out on top for me was the oldest Magellan in the shop!! Big text, quick sat fixes, rapid updating when moving,,,,,,,,,,,,the cheapest in the shop and just what I needed with no "doo-dads' that I don't need.

There's only 2 makes really. Garmin and Magellan. I've had Magellan since GPS first came out back around 1986 or so and I've never liked Garmin. But the Magellan after sales is crap and the last one I had was a PIA as it was impossible to get the four things I needed all one display screen – Position, distance to go, bearing and heading!! This is basic stuff and yet the GPS software couldn’t do it!! Work out what ya want it for and test run the one ya fancy. Forget “do-dads” unless ya need ‘em.

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Re: Lets talk GPS

Post by Guest on Mon 04 Mar 2013, 8:50 am

Hi Caterpillar,

I use UTM but have had difficulty trying to zero in on a coordinate taken from Google Earth, my gps was an Etrex (yellow) which the missus has now as i just brought the newer Etrex 20.

I would get close to where it was on google and use the etrex to zero in but i would take a reading and work out that it was about 100m south and 600m east, head off out there and i find i should have gone west instead of east.

I think the confusion(could be me!!)was that Google Earth has Nthings and Ethings and me Etrex had something different. I never did work it out, I just kept driving one way and finding that i had to go the other way to actually get to where i needed to go

Does anyone else have this problem?, my missus is "Directionly Dislexic" and i really should sort this out before we head off for the new season

Ron

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Re: Lets talk GPS

Post by Guest on Mon 04 Mar 2013, 9:36 am

Ron,

I think I may know the answer to this one. Firstly, for some odd reason I've found co-ords on Google Earth can be slightly incorrect AT TIMES. Why, I don't know. But the error of "go west instead of east" is caused by "Americanisation"!! Google is an American product and as usual it's made for use by Americans in America as a priority. When entering UTM co-ords into some mapping programs such as "Oz-Explorer" for example, one needs to specify whether you're in the Northern Hemisphere or the Southern Hemisphere. Otherwise the GPS reading is the wrong way around. This may be the issue with what's happening to you.

Now I've never taken a reading off Google Earth to put into a GPS, so I haven't experienced the problem or how to get round it, but I will do some "playing around" and get back to you. I have a caravan to paint just now as the sun has finally stopped beating down here in Perth today!

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Re: Lets talk GPS

Post by Guest on Mon 04 Mar 2013, 9:42 am

when u finish yours CAT u can get a leave pass and come up here and start on mine..
got a quote to put some lino in the old girl --a strip of about 21' =$891.00 mmmm might pass on that one..

regards
oneday

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Re: Lets talk GPS

Post by Guest on Mon 04 Mar 2013, 9:48 am

Ron,

Tell me PRECISELY each keystroke that you enter into your GPS when you take a reading off Google Earth.

e.g - lets say we're taking a reading of somewhere you know, put the reading on here. I need to see what text and numbers that you're putting in your GPS. The readings on Google Earth are shown in UTM - but they are shown as "metres east" & "metres south" - which is for the northern hemisphere. For the southern hemisphere you'll need to enter that as "metres east" & "metres north".

Hopefully that will fix it - fingers crossed.

Cat

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Re: Lets talk GPS

Post by Guest on Mon 04 Mar 2013, 9:53 am

oneday monday wrote:when u finish yours CAT u can get a leave pass and come up here and start on mine..
got a quote to put some lino in the old girl --a strip of about 21' =$891.00 mmmm might pass on that one..

regards
oneday

Pay for the flight up there & I'll do it!! After years in O&G I only fly "business class",,,,,,,,,,,,,

PS - forget the lino. Just get some of those foam mats with holes in, cheap from Bunnings, and lay 'em on the van floor. Dead easy to clean out - just rip 'em out and bash 'em and put 'em back and they're very pleasant underfoot.

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Re: Lets talk GPS

Post by Flying kiwi on Mon 04 Mar 2013, 10:36 am

never had many issues putting google earth coords into gps. they can be a bit out sometimes i think this is due to the photos being slightly out when put into GE.
on GE under settings you can change what form of coords you want to work in make sure your gps is on the same setting and it should be all good.
the yanks can also dumb down the GPS system to non millatary recivers in times of war (or whenever they feel like it), this makes you GPS jump all over the place up to about 500m rather than send you to precisely the work spot though.

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Re: Lets talk GPS

Post by Bignuggs on Mon 04 Mar 2013, 11:19 am

I posted this last year but it makes you think.

Here's the interesting bit, it comes from an old Choice Mag (Dec07/Jan08). Make of it what you will but it brings me back to my thoughts on the JORN stations we have in WA.

Soon after it was created, the civilian GPS was doctored by the US government,
which incorporated an artificial inaccuracy (up to 100 m) to counter any potential
terrorist threat.
• Bill Clinton removed this restriction in 2000, arguing that the public good to
be gained through using as accurate a system as possible would outweigh
any security concerns. However, the US government still reserves the right to
introduce selective availability if it feels its national interests are threatened —
for example, during the war in Iraq, where the civilian GPS has been made
inoperable within the war zone.

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