I need help with your GPS 12MAP (yes yours!)

[+ArnieBarney]

Does anyone own a funtioning Garmin GPS 12MAP or perhaps GPS IIIPLUS which I think is equivalent and is willing to commit a few minutes to convert user grid coordinates to lat/long? It is for an interesting old puzzle cache.

[7rxc]

Have you tried any of the converter programs like Fizzy Calc or even the one online as Other coNversions etc.?

 

Thinking a bit more on your basic problem of the puzzle... I seem to remember one that used something unique in the way the coordinates appeared on the GPS screen, Is it one of those... Other than that I don't know, but I seem to remember that many of the early Garmins shared that 'appearance' thing, but can't remember what it was it was back a while. I do remember using my 45xl to do it.

 

Doug 7rxc

[+ArnieBarney]

I own a Garmin Oregon and if I enter the parameters in the user grid it puts me way off, thousands of miles off. I think it may have been the coding in those old units which allowed for a particular conversion. I am just curious if it really works. Here are the parameters for anyone who can do this and send me the coordinates.

 

SET USER GRID AS FOLLOWS:

 

LONGITUDE EAST 019 DEGREES

SCALE +0.9996000

FALSE EASTING +20000.0

FALSE NORTHING +30000.0

 

SET USER DATUM AS FOLLOWS:

 

DX +99999 meters

DY +99999 meters

DZ +99999 meters

DA +99999 meters

DF +9.9999999 meters

 

THIS CACHE IS LOCATED AT:

 

USER GRID 1725951

9980984

[7rxc]

Not what I was remembering at all... Don't think the 45xl will do that, but I was just given a Magellan GPS 2000 that does.

 

I just got the 2000 working at all and will explore that for you.

 

I'll send you an email, since this is going towards the dreaded 'solve online' situation that is not for forum use.

However there is no such problem with direct communications... watch either PM or email via profile.

 

Doug 7rxc

[+ArnieBarney]

This relates to an archived cache. It may be that geo-trash is still out there. Feel free to PM me. I have attempted to contact some owners 12MAP's directly but sadly they didn't respond. These are 13 year old vintage units so you will have a hard time finding them so my plea is to any owner of one to dust off their 12MAP and let it have one last hurrah.

[7rxc]

I've already sent you this, but for others, it will shed some light on the problems involved in setting a user grid.

 

Playing around with my Map 60cx and several others I keep having problems... First off to me this is is in newer units, not old ones.

I now feel really old, like most of my GPS units. Sigh!

 

First the explanation from a web site I found then lost (looking again). Aha got it!

 

Edit:

Working with Garmin Receivers #5

 

==

 

User Defined Grid

 

Many Garmin units support a user defined grid. This can be used to support grid systems that are not supported directly by the receiver. Unlike the user defined datum however a user defined grid may or may not be successful. For example the map that contains the grid you are trying to emulate may be using a different projection than the one assumed by the user defined grid. In addition the allowed references that are displayed may not match the grid you are trying to emulate. For example you cannot match the typical map grid that has letters running one way on the map and numbers the other since the display always works with numbers in both directions. The user defined grid is really just a modification of the UTM grid and assumes a Mercator projection. And, like the UTM grid convention it does not work well with negative numbers so any grid defined should ensure that the numbers will always be positive.

 

To define a grid you will need to specify the grid origin as lat/lon and then you can specify a scale factor for the grid and a false Easting and a false Northing in meters. When you first enter the user defined grid settings you will find the values for UTM already entered into the unit. Change these values to match the requirements of the grid you need. If the projection system is different you can still get close approximation for a given local area. You may need to adjust the numbers as you move further away from the origin where you defined them. Don't forget that you may need a different datum, perhaps a user defined one, for your user defined grid. Often though you will be able to use the work someone else has done to define the grid you are interested in and you can just enter the data without having to design it yourself. There are web resources that can be used to define some of the grids you may want.

 

An example

 

Suppose you want a local grid of your own that measured distances in feet, here is how to proceed.

 

Pick an origin for the grid. Note that this must be in the lower left corner (SW) of the area the grid is to cover. You can't have any negative numbers in your grid.

Go to the origin point and note the lat/lon numbers.

Enter the longitude for the origin.

Enter a scale of 3.280839895 (This converts metric to the international foot at sea level. For metric you would enter 1.0)

Enter a false easting of 0

Enter a false northing of 0

Save this configuration.

Go look at your coordinates and write down the numbers.

Now return to the user defined grid and enter the numbers you just wrote down as negative numbers in the false easting and false northing.

Save the new configuration.

Check your waypoint location which should now read 0,0. Remember negative numbers will not work so if it drifted a bit you may have to move.

Use your new system.

Thanks to Jerry Wahl for the idea behind this discussion. Dayton Fraim wrote me and said that sometimes you can't get to the lower left corner as a starting point or your origin needs to be a location that is not at the corner of your grid reference (He lives on an island where the origin might need to be out in the water.) so you might want a modification to this procedure. The idea is to use the same trick as UTM does by adding a real false easting and false northing to the above procedure. Instead of just adding the negative numbers in the false easting and northing in the above procedure to make the answer some out to zero you could add an offset to these numbers first such as adding 10000 to each negative number. Then save your new configuration and check your waypoint location which should read 10000, 10000 or whatever offset you chose. This offset will need to be factored into any grid values you use for your work so a simple number is best. Using this offset will prevent the negative values problem.

 

==

 

The obvious thing is that one needs to 'correct' the coordinates by adjusting the User Grid parameters.

 

Most of these User Grids are quite local in area, Like many of the finder logs there, there is a problem seeing the coordinates entered in a waypoint when it is out of range of the local grid. One can't simply expand the grid for the same reasons normal grids don't often do that. UTM sounds like one grid, but is actually applied in 6 degree zones. After some playing around I found the ones posted here just off of Suriname in South America. I'm trying to see what it takes to 'correct' that (applying the two mile rule for finals, which might not be valid given the age of the cache when published).

 

At any rate, I'm interested in this 'new to me too' aspect of my GPS. Thanks for that!

 

Doug 7rxc

Edited June 15, 2012 by 7rxc

[xyzee]

My 60Cx is showing it almost off of the map, in North Russia.

[+ArnieBarney]

I hope someone with a 12MAP sees this message and can try inputting this

[7rxc]

Another place on that same GPSinformation site...

 

This gives some examples and an explanation of process below those.

 

Emulation Information

 

Not exactly what you want, but anything that gives information about the actual process used is helpful.

 

Doug 7rxc

[+ArnieBarney]

a latitude of S 45 deg and a false northing of 4330000m looks more realistic on my unit as it puts me near the 49th parallel. Now to find a longitude origin. The northing coordinates is approximately a quarter of the radius of the globe, or am I barking up the wrong tree?

[7rxc]

a latitude of S 45 deg and a false northing of 4330000m looks more realistic on my unit as it puts me near the 49th parallel. Now to find a longitude origin. The northing coordinates is approximately a quarter of the radius of the globe, or am I barking up the wrong tree?

Well... I'm not getting anything on the puzzle end, but am getting more 'into' how it works in general. I made one change to the 'settings' that got me into BC. right or not? I'll email again.

 

On the big question to me... Does your GPS have a place to enter the latitude in user grid? My Map 60cx only allows for longitude.

There have been changes since User Grid was made an option. My choices are the same as the ones you listed for the Map 12.

 

Dumb me, I forgot to record the 60cx user grid default settings before changing them. Trying to avoid a reset, ANY one know the

original defaults for first time access to the user grid? Not that much different from the stated ones but I remember changing some besides the longitude. Thanks. I can probably work it out by comparison but I'm lazy. Garmin FAQs don't seem to mention such things.

 

I'm trying to keep this to discussing USER Grid use here and out of the forums re the puzzle solution for the usual reasons even though the specific one is archived.

 

Doug 7rxc

[+ArnieBarney]

Yes my Oregon can enter latitudes. In order to get close to the original cache coordinates I had to adjust the latitude down to South 45 deg. I presume the default is to start at the equator but you should be able to set a different origin as I stated earlier.

If you never worked with the user grid settings before it should have been blank but mine seems to remember the settings even if I swing back to normal use and back to user grid settings.

I did notice that when I enter the user grid coordinates and check the temporary waypoint, it is not accurate. I am in close proximity but the device gives me a "random" location. I can then set the the right waypoint by zooming in on the screen and pinpointing the exact coordinates and watching the UTM numbers appear. I can then set that as a waypoint and note the deg lat/long numbers.

I am still hunting for a 12MAP to confirm the differences between my assumptions and what the old device actually does. If it does give coordinates to the cache, so be it. I can probably create an updated version of the cache with new parameters that work for current gpsr's. This discussion sure has enlightened me on some aspects of user grids. It seems to be an art unto itself.

[xyzee]

Doug,

When on the User UTM Grid page, hit Menu>Restore Defaults>Entr to see the original settings. Now you can hit Quit, and reselect the User UTM Grid, which will have the new settings, or hit Save, and keep the Defaults.

I found how to do this from having one of my "Senior Moments" by forgetting to hit Save.

 

On the 62s, that I had for a short time, the format on the User Grid page was changed to include the Lat, but it was still tied to the Equator, like on the older units, meaning that I still had to enter a - number to use in Utah.

 

The older Magellans are a lot easier to use, as I can enter the Lat/Lon of the SW cor of this property and work off of it.

[7rxc]

Doug,

When on the User UTM Grid page, hit Menu>Restore Defaults>Entr to see the original settings. Now you can hit Quit, and reselect the User UTM Grid, which will have the new settings, or hit Save, and keep the Defaults.

I found how to do this from having one of my "Senior Moments" by forgetting to hit Save.

 

On the 62s, that I had for a short time, the format on the User Grid page was changed to include the Lat, but it was still tied to the Equator, like on the older units, meaning that I still had to enter a - number to use in Utah.

 

The older Magellans are a lot easier to use, as I can enter the Lat/Lon of the SW cor of this property and work off of it.

 

Thanks, I'll try that! Have you had any luck with the problem itself, if so we are having a sort of discussion of that via email or PM to keep the solution out of the forums (fora?), for those who seek such things for other puzzles.

 

I'm getting a bit behind on it because of local things, but hope to be clear for more.

 

Doug 7rxc

[xyzee]

I set up a GPS 60 and a 60Cx, with the data listed above, in the User Grid and User Datum, and get the same results in both units: in North Russia. In the Demo mode or GPS on. I made a waypoint and entered the cache User Grid numbers, and it changed them to:

2138372

9654707

Which is still in N Russia.

Then I panned the white arrow on the Map page to line up the numbers listed above, which is way up N in Russia.

 

I've been using the User Grid for years, with the Garmin 60 series and the older Magellans, for State Plane in the US, so I must be overlooking something.

I'll try my hand at doing the PM thing tomorrow, when I have a clearer head.

[7rxc]

I set up a GPS 60 and a 60Cx, with the data listed above, in the User Grid and User Datum, and get the same results in both units: in North Russia. In the Demo mode or GPS on. I made a waypoint and entered the cache User Grid numbers, and it changed them to:

2138372

9654707

Which is still in N Russia.

Then I panned the white arrow on the Map page to line up the numbers listed above, which is way up N in Russia.

 

I've been using the User Grid for years, with the Garmin 60 series and the older Magellans, for State Plane in the US, so I must be overlooking something.

I'll try my hand at doing the PM thing tomorrow, when I have a clearer head.

My try accepted all the first settings, after I figured out it would not display the coordinates at all in the UG format, I switched to standard UTM for it to 'convert' and got it to display at 25M 0364484 9868156 in the South Atlantic near Suriname. Go figure.

Nothing to be seen up north. With a 'northing' value that high it would be south of the equator. That was with no shifts.

 

I understand the hows, but not the whats that are occuring. Aside from the puzzle itself, I can't figure out why something centred on 19 E could display near South America at all given the false values. I've been looking at that 'northing' value in the offered settings in conjunction with the 19 value as both being off base. Both of us have managed various means to force it into the right (guessed) area, but that doesn't help with the puzzle solution.

 

Still have to try the recovery of my default settings though, maybe tomorrow.

Watch your email.

 

Doug 7rxc

[+Cardinal Red]

SET USER GRID AS FOLLOWS: SCALE +0.999600

 

Enter a scale of 3.280839895 (This converts metric to the international foot at sea level. For metric you would enter 1.0)

 

Several years ago I took a brief interest in User Grids. I scoured the web, and came up with some information that seemed to explain why the default SCALE FACTOR was .9996

 

I came to this forum trying to get someone to confirm what I had read. Not a nibble. Now I see that 7rxc is proposing a scale of 3.280839895

 

That seems to be a comparison of a scale factor and a metric conversion. The metric conversion certainly doesn't seem to fit the little bit I thought I knew about UTM User Grid.

 

Can anyone throw some more light on both the UTM User Grid SCALE FACTOR .9996 and/or 3.280839895

 

What, where, why?

[+ArnieBarney]

I'm imagining the scale factor relates to a 1:2500 scale map. But all the other factors make me think this is exploiting a bug in the Garmin GPS 12MAP type units.

[7rxc]

SET USER GRID AS FOLLOWS: SCALE +0.999600

 

Enter a scale of 3.280839895 (This converts metric to the international foot at sea level. For metric you would enter 1.0)

 

Several years ago I took a brief interest in User Grids. I scoured the web, and came up with some information that seemed to explain why the default SCALE FACTOR was .9996

 

I came to this forum trying to get someone to confirm what I had read. Not a nibble. Now I see that 7rxc is proposing a scale of 3.280839895

 

That seems to be a comparison of a scale factor and a metric conversion. The metric conversion certainly doesn't seem to fit the little bit I thought I knew about UTM User Grid.

 

Can anyone throw some more light on both the UTM User Grid SCALE FACTOR .9996 and/or 3.280839895

 

What, where, why?

 

Firstly, I'm new to this, BUT the line you quoted was from an article that I quoted... not from ME!

 

However... what I see is that the scale is what helps keep the shape of the map, I think they use conformal as the term.

At the equator the size in meters for 6 degrees is fairly wide and at the poles gets down to about 0. The scale for a grid may have to do with the reduction as a relation or function of latitude. Also seems to be sort of reversed at first glance, with a low number for the north end causing lots of expansion whereas the equatorial is close to 1 and not much change. I could be wrong about that though, just what I see. .9996 or whatever is the normal used by UTM. As for the 3.28033 and such... that was the quoted example for converting from metric to feet. one meter is 39.36 inches or 3.2 whatever feet... that was the units used in the example of a custom grid made for that usage.

 

Wish I understood it as well then as now.

 

Doug 7rxc

[+Cardinal Red]

I'm imagining the scale factor relates to a 1:2500 scale map. But all the other factors make me think this is exploiting a bug in the Garmin GPS 12MAP type units.

My understanding is that the function of the SCALE FACTOR is to "reduce the distortion of the projection in the area of interest". The SCALE FACTOR of .9996 applies to a 6 Degree wide UTM zone. After an extensive online search, I once found an easily understood mathematical explanation for how .9996 was calculated (that site has apparantly since gone dark).

 

For what it's worth, the scale factor was supposedly derived from the Cosine of 1/4 of the width of your zone. Standard 6 degree UTM zone divided by 4 = 1.5

Cosine of 1.5 = .9996 (a unit-less number).

 

If you were working with a narrower custom zone, say 1 Degree wide, the distortion should be less (closer to 1). A 1 Degree zone divided by 4 = .25

Cosine of .25 = .9999 (a unit-less number).

 

While that makes a nice convenient story, I can not find a confirming source anywhere.