julianh

You can download the Shareware/Demo and Trial versions of OziExplorer for free and give it a test at no cost. Note that OziExplorer will display maps on your computer screen, but will NOT upload maps to your GPSr, only Waypoints, Tracks and Routes. From the web-site: The Shareware/Demo version is missing many features that you get in the full purchased version . But it does allow full communication with the GPS for upload/download and moving map . Only allows maps in BMP image format to be loaded . Only loads maps in WGS84 datum The Trial Version has almost all the features of the full version (works with all supported image formats and datums) but with these limitations . No communication with the GPS for upload/download . No saving or loading of Waypoints, Events, Tracks etc . No saving of map as an image file . Will close down after 1 hour of running (must be restarted) Who knows - you might end up deciding it's actually useful, and buy a full licence, like I did! Hope this helps!

There are many ways to achieve what you are trying to do - e.g. check out OziExplorer: http://www.oziexplorer.com/

... and since consumer hand-held GPS is only accurate to within about 3 to 5 metres or so under ideal conditions, both formats can be considered to be equally "accurate" as far as locating a cache is concerned!

Easiest way I know is to test it for yourself: 1. Go to a location which you can easily find on Google Earth or similar, and which has a good line of sight to an easily recognised target a couple of km away or more, which you can also find on Google Earth. (Your front door might do fine as a sighting location, if you can see a nearby hill or tower! ) 2. Calibrate your compass. 3. Assuming you have a Garmin, do a Sight'n'Go. Make a note of the bearing angle to your target. 4. Repeat the Sight'n'Go a few times. This will give you a good idea of the repeatability / accuracy of the Sight'n'Go procedure. If you are getting more than a couple of degrees variation, you are probably not holding the unit sufficiently level when taking a sighting. (I believe this is less of an issue with the newer models with 3-axis compasses.) 5. Check the actual bearing from your location to your target with Google Earth. I find that I can easily get better than 2 degree accuracy with my Summit HC, and I can then use the compass in "Course Line" mode to navigate "blind" to my destination. In Course Line mode, you get a course line between the start and end points and an offset indicator, instead of the more common red arrow. When you are navigating cross-country to a sighted target (such as top of a hill, tall mast or similar), you don't know the true coordinates of your target, or how far the target is from your start point; you may only know the direction it was located from your start point. The Course Line indicator lets you navigate along that original straight line, and you can get back on track even when you have to deviate through thick undergrowth, around creeks, etc. Hope this helps.

I don't now about the specifics of geoid fluctuations "out where you live" (Colorado), but here in Australia, the geoid to ellipsoid correction has a variation of around 5 to 10 metres or so for every 5 degrees change in latitude or longitude - see for example page 3 of http://www.ga.gov.au/image_cache/GA5175.pdf The correction varies from about -31 metres in south-west Western Australia to about +61 metres at the northern tip of Cape York. As far as I can tell, it is not that different in the USA (even allowing for the "large bumps" a.k.a. "The Rockies") - e.g. see http://www.ngs.noaa.gov/GEOID/images/2009/geoid09conus.jpg Given the inherent limitations of consumer GPS elevation accuracy (plus or minus 10 metres or so), recording the geoid corrections on a 1 degree x 1 degree grid and using interpolation for local correction would be well within the limitations of a consumer hand-held GPSr (in Australia, at least). (You would need a more refined model for professional survey-accuracy GPS, but that is a different subject, I believe.)

I believe it's programmed in as a look-up table; not sure of the resolution (possibly just 1 degree x 1 degree), but it just uses your current latitude / longitude to interpolate the local height of the geoid above / below the ellipsoid, and then uses that correction to adjust the reported elevation to be against local MSL. Since consumer GPS elevation is only good to a couple of metres at best, you don't really need super-fine resolution of the Geoid correction data to get an acceptable correction.

GPSlug said: "But seriously, since "elevation" is already being used in GPS receiver software to describe the angle of a satellite, it isn't usually used to describe the height. That would just be confusing." OK - now I'm confused! On my Summit HC, the available altimeter data fields are called "Elevation"; "Height" is not one of the choices. The satellite page does not give me an option to view the satellite elevation and azimuth angles; all I can get is a crude "sky map" showing me roughly where the visible satellites are located. As has been pointed out by others here, the term "elevation" means different things to different people in different contexts; however, plenty of people use "elevation" to mean: "The elevation of a geographic location is its height above a fixed reference point, most commonly a reference geoid, a mathematical model of the Earth's sea level as an equipotential gravitational surface." Ref: http://en.wikipedia.org/wiki/Elevation (Yes, I know that Wikipedia is not the most authoritative reference, but it does indicate that this is in common usage!) Red90 said: "Elevation on the GPS is height above the ellipsoid (that you have set in the setup) as stated above. Nothing more fancy than that." Not so - on my Summit HC, the elevation (i.e. "Height above MSL") is given above or below the geoid, not the ellipsoid.

I don't really want to pour petrol onto the fire, but when discussing reported GPS elevation, don't forget that the WGS84 specification has both a reference ellipsoid (which is a slightly flattened sphere), AND a reference gravitational equipotential surface (geoid) which sets local MSL above or below the reference ellipsoid. See http://en.wikipedia.org/wiki/Geoid and http://upload.wikimedia.org/wikipedia/comm...6/Geoids_sm.jpg for a bit more information on the undulations of the geoid (surface of MSL) compared to the more simple ellipsoid. I am 99% sure my Garmin Summit HC is programmed to report elevations against the geoid (i.e. elevation above or below local MSL), and it always shows an elevation of pretty close to 0 metres when I reach the coast on any of my travels (including Australia, South Pacific, Europe, South-East Asia, South America, etc). I am 99% sure that my car SatNav (a cheap Chinese import) reports elevation against the ellipsoid. (Either that, or my car SatNav is using an incorrect geoid specification.) Here in south-east Queensland, it consistently shows elevation around 20 to 30 metres higher than standard topo charts, etc. Elevation above MSL is of no consequence for car navigation purposes, so it really doesn't natter that they don't seem to have programmed the geoid corrections into the unit. However, it means that while the reported elevation gain / loss is reasonably accurate, I can't easily correlate my car SatNav's reported elevation against detailed topo maps, elvation markers, etc.

The difference is in the SENSITIVITY rather than the ACCURACY. When both units have a reasonable fix, they will yield pretty much identical position coordinates. However, all of the H-series models (high sensitivity) will get and hold a fix where older low-sensitivity units will not. Low-sensitivity units will typically have trouble getting or holding a fix in canyons, under moderate tree cover, in the "urban jungle", etc. High-sensitivity units can typically get and hold a fix deep in canyons, under very heavy tree cover, deep in the street canyons of New York, and often indoors as well (very handy if you forget the way to your bathroom!) Don't even think about it - get a high-sensitivity unit!

Gotta have MASSIVE respect for this guy (Sean Carney): http://www.seancarney.ca/blog/2010/09/03/geocaching-is-fun http://www.seancarney.ca/projects/arduino-...uino-gps-system Not content with the usual challenges of geocaching, he has scratch-built his own GPS receiver, using an Arduino http://www.sparkfun.com/commerce/product_i...products_id=666 , a SparkFun GPS Shield http://www.sparkfun.com/commerce/product_i...roducts_id=9817 , and an LCD Keypad Shield http://www.nuelectronics.com/estore/index....p;products_id=2 , packed it all in an Otter-box, and then used THAT to go geocaching. Excellent!!!!!

Evidence? mA consumption per spec sheet, meter measurement, anything? I'm guessing you're thinking of the older models. 7.3 milliamps at 3V wasn't exactly what I'd call a "battery burner", and that was the old 2-axis spec when these parts were a less efficient. Newer 3-axis chips draw a whopping 0.8 milliamps at 1.8V! I'm guessing the 14 seconds (or whatever it really is) that one of these would take out of a normal caching day could be afforded by even the most battery-frugal individuals. If you are after evidence, a search on this forum for "current compass" will reveal tests that a number of us have carried out; e.g.: http://forums.Groundspeak.com/GC/index.php...=176064&hl= Bottom line - on most recent models, don't worry about the current drain of the compass - the back-light is the real "battery burner". Hope this helps!

You have dropped a digit in the second coordinate. UTM has 6 digits for the first coordinate (the easting, in metres), and 7 digits for the second coordinate (the northing, also in metres). Did you mean to specify: 10 S 580000 4175500 which would put you on Grovenor Drive, about 10 km east of San Francisco Bay. As for the rounding of the last digit - that's just a consequence of the finite resolution of the GPS, and the conversion between its native latitude / longitude location to UTM coordinates. It's only a 1 metre shift - you should still be able to find where you want to go! Hope this helps!

Not for me, thanks! I think a human readable location is far more likely to be useful than a non-human readable "postcode".

What your GPSr REALLY does is something like this: It picks up and synchronises to as many satellite signals as it can. The it calculates your 3D location using binary mathematics, with however many bits the software and hardware support (32-bit, 64-bit, or whatever), and using whatever basic coordinate system it is programmed in. My guess is that the deep-down maths is calculating your real-time position in a spherical coordinate system, measuring azimuth and altitude in radians, and radius in metres, with the three coordinates being saved in (say) 32-bit floating point binary notation. For display purposes, it then converts these three coordinates into the user-selected coordinate system - latitude & longitude, UTM, or whatever. Notwithstanding that the accuracy of the whole GPS system is limited to a few metres, it makes perfect sense to carry all available digits of precision through all calculations. However, the displayed accuracy should probably be formatted / truncated to a sensible precision. Displayed location readings of better than 1-metre precision make no practical sense.

WHAAAAAT???? No. I didn't know that. There are NO instructions for the games in the manual. None. I don't know if you are kidding me or not... How would walking around help you with Gekoids, for instance? Or an other.... Are there supposed to be instructions for them somewhere? Yes, most of the games are intended to be played outdoors with a GPS signal. Download the Vista-C manual from: http://www8.garmin.com/support/userManual....ct=010-00368-00 It has a basic set of instructions for the Garmin games. (It is a much more comprehensive manual than what comes packed with most of the newer eTrex range, and 99% of the content still applies.) (You may conclude that it wasn't worth the bother, though - the games are pretty lame, but your kids might enjoy them! )

Let's not lose sight of what WAAS was developed for in the first place - it is essentially an aircraft navigation tool for improved accuracy, including the precision required for instrument approaches, etc. Essentially, WAAS is intended to enable aircraft to rely on GPS for all phases of flight, including precision approaches to any airport within its coverage area. http://en.wikipedia.org/wiki/Wide_Area_Augmentation_System Aircraft GPS systems use much more sophisticated electronics than consumer GPSrs, and have more sensitive antennae which are optimally located, etc, so they will be able to get by even if one of the WAAS satellites goes off line. Any consumer benefits arising from WAAS are just a side-benefit; I can't see the people who run the GPS system spending too much time or money responding to consumer complaints that they can't get WAAS!

Ummm.... Maybe I'm missing something here, but regardless of whether you are navigating in lat/long, UTM, or whatever, why not just make a waypoint of your destination, and then navigate to it? Your GPSr will tell you distance and bearing, updated in real time. Sorry if I am being a bit thick!

If you are interested in loading maps, particularly Topo maps, you should DEFINITELY go for colour - a crowded topo map with tracks, creeks, contours, etc, can be just about impossible to read in B&W. (Trust me, I know - my first mapping GPSr was a B&W Vista, later swapped for colour Summit HC.)

A couple of points to note: The eTrex series have a patch antenna, which should face upwards for best results (or more specifically, facing towards the visible satellites, if you have a poor visible constellation, with satellites clustered in a small area of sky due to shielding etc). Models with quad-helix antennas (like the 60 series) get best results when the antenna is pointing vertically upwards. If your eTrex is an original series, it will have lower sensitivity receiver, and will be more sensitive to loss of signal under cover, in ravines, when held at sub-optimal orientation angles, etc. The newer eTrex H and the 60 CSx both have high sensitivity receivers, and will generally hold a good signal under cover, and don't care too much which way you hold them.

Like any GPSr without an electronic compass, you have to be moving for the GPS receiver to be able to tell which way you are moving. Once you are walking at a reasonable (walking) pace, it should have no trouble working out whether you are going N, S, E or W. This is one reason why I still love my Summit HC (with electronic compass) - it tells me which way I am facing even when standing still. Hope this helps!

Nice that it's in the Register. Thanks for the link. But I'd like to point out that I used "Y2.01K Bug" at the top of this thread on January 3rd. Oops! How did I miss that?! Sorry - definitely not trying to steal your thunder! So, does S&AT get credit for first recorded use of "Y2.01k Bug"?

This issue has now been elevated to reach the attention of the general tech-press: The Register: Y2.01K hits Garmin sat-nav Routing like it's 1949 http://www.theregister.co.uk/2010/03/10/garmin_dates/ I wonder if this increase in exposure will get Garmin to actually do something about it? (Do I get naming rights for first recorded use of the term "Y2.01k Bug"? )

1,500 m horizontal / 800 m vertical is a pretty rugged hike (almost rock climbing!). Pythagoras' Theorem gives 1,700 m slope length, or a 13% error, compared to the 1,500 m horizontal measurement. Errors due to slope effect for more common "walking" gradients are much smaller - 1% or so.

Not so ... The main issue is to have a high-sensitivity receiver, and get the best line-of-sight to a window that you can. A window seat is best, but I have used my Summit HC successfully on many flights, including from an aisle seat, and even with my GPSr in my bag in the overhead locker, or under my seat. As was pointed out by others above, get a good lock just before you board the plane, and keep it turned on the whole flight, and you should be able to get a reasonable track-log for much of your journey. Trying to get a cold-fix from a moving plane can be difficult, but reacquiring a "warm" fix with a high-sensitivity unit is generally quite achievable, especially if you are near a window. You may get drop-outs from time to time, but it will keep sniffing out the satellites, and whenever it gets a 4-satellite lock (however briefly), it will resume tracking again. Note that the elevation record will be meaningless on units with a barometric altimeter in a pressurised plane, unless you switch the altimeter off so it records GPS elevation, not barometric elevation. Hope this helps!

I suspect it's a different bug from the Vista one, even if the symptoms are similar, because everyone seems to have suddenly encountered it at the beginning of this year. Also a hard reset didn't provide even a temporary fix, only a one-time fix. Try a Google search for "garmin wrong date" - it seems there are a lot of Garmin models which have been afflicted with this issue at various times; some have experienced it in the past (e.g. B&W Vista), while a few seem to have just taken a hit in 2010. Y2.01k bug?