Locating Your Position on a Paper Map Using GPS

[AlbinoNeutrino]

Hi All,

I've been lurking for a while and learned a fair bit already from the good people here, but I have a noob question that I would appreciate some direction with (pun intended).

I have a Garmin 62s with the garmin topo maps for Australia and New Zealand. I have been on a number of day hikes with the GPS and have figured out most of the basics of navigating with it, but am by no means an expert. I am trying to improve my map and compass skills at the same time and would like to use them together with the GPS.

I find that when looking at the maps on the tiny GPS screen it is hard to get a feel for the landscape and am much more comfortable looking at a paper map. What I would like to do is basically keep the GPS off until I need it, get a set of co-ordinates from it and then determine my position on a paper map. The map I am using is a map of the Bogong Alpine Area in the Alpine National Park in Victoria. It is a 1:50,000, has declination indicated and is using the GDA94 datum and "Transverse Mecartor Projection", whatever that is.

My GPS has no setting for GDA94 so I chose WGS 84 for the map datum, UTM UPS for the Position Format and WGS84 for the Map Spheroid, based on guesswork and a bit of power googling.

Have I got this right? What do I need to know/do to be able to get coordinates from the GPS that will match the paper map I am using?

Any help would be much appreciated, thanks.

[GPSGuided]

Zoom out and on the screen and it's not hard to match up on the location on the map. If you want a coordinate that's easy to use on a topo, then select UTM under Position Format and GDA94 under Map Datum on your GPS. I have those options on my Garmin and can't see why your doesn't. Go through the various Setup options carefully and you should find it. Also, don't switch the GPS on and off for location check unless you are prepared to wait a bit each time for the unit to achieve a good lock. Unless you are short on battery, just left the GPS on and refer to it as needed.

One other, Garmin regularly puts out firmware updates. It's always wise to compare your installed version and the latest and update as appropriate.

[AlbinoNeutrino]

Cheers, I had a proper look and found the GDA94. I could only find UTM UPS which I am assuming is the same as UTM.

Right after making this post I also found this online, which I am halfway through but seems quite useful for the task at hand: http://www.ascc.sinica.edu.tw/gis/gps/U ... 20Maps.pdf

Thanks for your help, I will try it out in the field and see if I can figure it out.

[icefest]

Hey,
Have you read this: http://www.icsm.gov.au/gda/wgs84fact.pdf
This paragraph is relevant to you:

[AlbinoNeutrino]

Cheers, I managed to find the GDA94 setting after a bit of digging,

[icefest]

There is less than a meter difference anyway, IMHO a bit of a non-issue.

If you can see 0.04mm on a 25k map then your skills are lost in anything but subatomic physics. You could see gluons with a light miscroscope.(I know it's not possible, they are smaller than 1/2 the wavelenth of visible light)

(Just Joking)

[Mark F]

I carry a map protractor with romer scales printed on overhead transparency film (about 1 gram). It makes transferring coordinates from the gps to a map very accurate. Just position the appropriate romer scale over the grid square.

I produced my own using the Open Office Draw application but most good drawing programs will do it.

[img]Map%20compass.jpg[/img]

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Map compass

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[GPSGuided]

Very clever Mark!

[icefest]

That's pure genius.

[AlbinoNeutrino]

Thanks, great idea. I don't own one, but I think some of the newer baseplate compasses designed to supplement a gps have romer scales printed on them too.

[AlbinoNeutrino]

You guys probably already know this, but I realised there are a couple of easy ways to figure out your position without using lat/long or UTM when I was half way up Mount Bogong yesterday.

If you know you are on a track, but aren't sure exactly where, get the elevation from your GPS altimeter and then find the matching contour line on the map. The point where the contour line intersects the track is your position.

I also created three waypoints in a triangle surrounding the area that I was walking in. If you take a bearing to two (or three) of these way points with your gps and then plot the lines on the map the point at which they intersect is your position.

[Mark F]

I have found that most compasses don't have 2 sided romer scales and often don't have a romer scale that matches the map scale I am using. Many US maps use 1:24000 and a few maps I have used in Europe have been 1:30K or 1:40K. The map protractor also provides an easy way to get a bearing from the map.

Yes, altitude is a really useful navigation tool, widely used in Europe. I find my Suunto Vector watch does a great job for this without having to get out the GPS. Whenever I reach a known altitude I calibrate the watch so the altitude readings will be pretty much spot on for a few hours. Getting altitude readings from a GPS can have quite an error. the Z axis is not gps's strongest point.

[GPSGuided]

I have found that most compasses don't have 2 sided romer scales and often don't have a romer scale that matches the map scale I am using. Many US maps use 1:24000 and a few maps I have used in Europe have been 1:30K or 1:40K. The map protractor also provides an easy way to get a bearing from the map.

If not already present, mark out the scale needed on my compass' base plate at home. Makes for easier reference out there.

[rucksack]

Mark F, you are right about Romer scales on baseplates and I do like your 'Romer construction'. Silva include three Romer scales on their Type 4 baseplate, which they use with their Expedition compasses. The current Silva Type 4 baseplate includes 1:25,000, 1:40,000 & 1:50,000 Romer scales, (with the 1:40,000 scale replacing the previous 1:63,360 scale on their older Type 4 baseplate). The baseplate of Silva's Ranger CL & CLQ compasses includes two Romer scales: 1:25,000 & 1:50,000, but all other Silva models seem to be sans Romer. Recta include a 1:50,000 Romer scale on the baseplate of their 420 & 420G models, but on none of their other models and as far as I can see, neither Suunto, nor Brunton have any baseplate compasses with Romer scales.

I have used an Silva Expedition 54 compass for a long time and I think that Silva has always included Romer scales on their Type 4 baseplate. I wholeheartedly agree: having Romer scales on a compass baseplate makes for a much more precise transfer of coordinates from GPS to map and also for being able to communicate much more precise grid references. The Silva Expedition 54 compass also incorporates a sighting function, which Silva claims makes navigational calculations potentially accurate to 0.5º, so that helps too. If I am walking extensively off-track, I tend to take a Douglas protractor with me, as well, as that little bit of plastic can also help deliver navigational accuracy. All good fun!

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[rucksack]

Silva Expedition 54 compass with Romer scales.jpg (164.76 KiB) Viewed 30070 times

[rucksack]

My protractor weighs 24g and has a surface that can be easily written on with a pencil, often obviating the need to write on the map itself. After I finish a calculation, (if I need to make one), I can quickly erase the pencil scribblings on the protractor. Non-GPS navigation is becoming an arcane art for some, but it is still an enjoyable one for me. I have used a GPS since 1999, but I do appreciate the process of navigation and on many walks, I find that I never actually turn on my GPS, or I leave it at home, especially if I am walking in an area that I know well, even when that area is mostly off-track.

rucksack

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[corvus]

G'day rucksack,
Interesting to see that you use a Douglas protractor do you have an Australian made one from W&G I have owned and used mine on and off for over 30 years (btw mine weighs 31g with it's case) together with my Silva(switched to Suunto M3 with better romer scales) Compass,have to admit being a bit of a Luddite with GPS and I guess I don't really use them to the best of their capacity .
corvus

[rucksack]

Hi Corvus.

My protractor was made in England by Blundell Harling. It is their 130mm version and they still make these and a larger 250mm version too.

See here: http://www.blundellharling.com/products.asp

I didn't notice any Romer scales on the baseplate of the Suunto M3 compass. I attach a photo of a Suunto M3 compass that I found on their web site, but it has no Romer scales. What does yours look like? (The version that I found on their web site has 1:15,000, 1:20,000, 1:25,000 and 1:50,000 scales, but not the right-angle Romer scale.) I think that I am right in saying that Suunto also own the Recta brand and the Recta 420 & 420G compasses do have a 1:50,000 Romer scale on their baseplate, but I haven't come across Romer scales on any of the Suunto branded compasses. Does the baseplate on your M3 look like the attached photo, or is it different? (I am assuming if it has Romer scales, it is different.)

I have a few Silva compasses (5 at last count), but haven't had much luck with Suunto compasses. I have had two Suunto diving compasses and both expired after not a lot of use. (Seawater is not kind to compasses.) I have also had a Suunto GPS Global baseplate compass and, from memory, that one lasted for some 12 or 13 years. I mostly rely on my Silva Expedition 54 for walking in Australia and a Silva Voyager 8010, when I am walking in Asia. The Silva Voyager 8010 has a bright yellow baseplate stamped 'Made in USA', which means that it, (and the actual compass too), were made by Brunton when the two companies had a tie up. The The Silva Voyager 8010 is a globally balanced compass, but it does not have any Romer scales marked on its baseplate.

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[rucksack]

And here is my globally balanced Silva Voyager 8010. The baseplate of the Voyager 8010 features 1:25,000 & 1:50,000 metric scales and 1:24,000 & 1:63,360 imperial scales, but no Romer scales. Notwithstanding the Silva logo printed on the 8010's baseplate, the compass is obviously a Brunton.

rucksack

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[rucksack]

And, if we are talking 'old school' navigation, we are also talking about one of these ...

rucksack

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[GPSGuided]

And, if we are talking 'old school' navigation, we are also talking about one of these ...

Nay. I walk my fingers.

[rucksack]

Indeed GPSGuided. Indeed. I once walked with a chap in my old university walking club who had mislaid his one and only compass for more than a year and instead of buying another one, he used his rather ancient analogue wrist watch as his compass. He also used his fingers as his map measurer: middle finger for 1:50,000 scale maps and two fingers side-by-side for 1:25,000 scale maps, if I remember correctly. I walked with him a couple of times and he never seemed to get lost, or lose his way, so who is to say. It was certainly a cheap set up and obviously saved on batteries. Might have been more interesting, of course, if he ever found himself navigating in heavy cloud, or thick fog on a particularly overcast day.

rucksack

[corvus]

G'day rucksack,
Thanks for that, had another good look at my Suunto M3 and it does not have Romer scales just the 1:25000 measurement + others also consternation in my household as to the whereabouts of my distance map measurer
Interesting that W&G are still showing as selling Douglas protractors at around less than 1/2 the price of the nice Blundell Harling ones
Must admit to using the Digital Compass on my watch when required and my reliance on the visability of the Sun and Stars if needed (not pin point I know but I will at least have some sort of direction ) and I like the idea of finger scales.
corvus

[3rd weekender]

this might be a bit late but i found a heap of map tools at www.maptools .com ( john carnes) is the man from us he sent me some tools and a handy book on the subject