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Hi,

I apologize for a total newbie question. I'm really new to all of this.

I've been Googling around about WGS84 and I read that the current version was released (if that's the right term) in 1984 (hence the name), was revised in 2004, and is only good until approximately 2010.

So my question is...if you have a WGS84 coordinate written down in 2003 before the revision, how exactly would you go about trying to find that point? All the online webpages and GPS devices are updated with the 2004 revision. Is there some kind of conversion you can do to the coordinate so that you can locate it with the current datum? Or do you need to get a 2003 map and look it up manually (I'm looking for the U.S.) Or would there not be enough of a difference to matter?

If you need a hard-copy map, could someone point me in the right direction of where to get one?

Sorry if this has been covered, but I couldn't find the answer by searching.

Thanks.

Anybody?

thus results in a—very theoretical—difference of 0.105 mm in the semi polar axis

It doesn't sound like the is much difference! I think the updates were to allow for continental drift...but I'm no expert!

I don't think that sentence applies to the 2004 update over the previous version. I think they are referring to WGS84 vs. whatever was used previously.

The problem is when I look up the coordinates using googlemaps, it gives me a point in the ocean when I know it is supposed to be dry land. I'm trying to figure out how to make adjustments so that it shows me the right place.

The problem is when I look up the coordinates using googlemaps, it gives me a point in the ocean when I know it is supposed to be dry land. I'm trying to figure out how to make adjustments so that it shows me the right place.

What point is that?

It's much more likely that it's either a coordinate format problem, or a problem with the map.

I would guess that it's a plus /minus (east/west)problem with the longitude......

I would guess that it's a plus /minus (east/west)problem with the longitude......

Any changes to WGS84 would be of the order of centimeters. It's not going to fix your problem.

I would guess that it's a plus /minus (east/west)problem with the longitude......

Any changes to WGS84 would be of the order of centimeters. It's not going to fix your problem.

Now Fizzy, you know better than that !

If written coordinates are input (into software or into unit) but the direction of longitude is incorrect, the error can be exactly as described.

The WGS coordinate you wrote down in 2003 was most likely WGS84(G1150) which is based on ITRF2000. the new WGS84 should be based on ITRF2004. The difference is small enough that it is inside the accuracy limit of your GPSr. Although I didn't research it, the difference is probably only a few inches at most. WGS84 is generically thrown out there a lot when it is in fact usually one of the later adjustments (based on ITRF91,ITRF94, or ITRF2000). If your point is falling out in the ocean in Google Maps, most likely the cause is your input is being interpreted as an East Longitude. Try the same input, with a negative longitude to signify West longitude. This input works ( 45 15.221' N 122 12.258' W ) as well as ( 45 15.221' -122 12.258' )

Any changes to WGS84 would be of the order of centimeters. It's not going to fix your problem.

If the difference is so small, why did they need to come out with an update in 2004?

Any changes to WGS84 would be of the order of centimeters. It's not going to fix your problem.

If the difference is so small, why did they need to come out with an update in 2004?

Because for some applications, this difference is big enough to be important?

If your point is falling out in the ocean in Google Maps, most likely the cause is your input is being interpreted as an East Longitude. Try the same input, with a negative longitude to signify West longitude. This input works ( 45 15.221' N 122 12.258' W ) as well as ( 45 15.221' -122 12.258' )

Hi,

I have been using the negative longitude.

It's not hugely off. The location should be somewhere in Rhode Island, and Google Maps shows it just south of Block Island, in the water.

I was hoping that the difference in WGS84 before and after the upgrade would be enough to put me on dry ground.

If the point is falling too far to the East by 150-200 feet, it could be that your coordinate is NAD27. NGS has an online tool for converting. http://www.ngs.noaa.gov/cgi-bin/nadcon.prl use NAD83 for WGS84, as they are pretty close to each other.

No, actually it's too far South.

Let me ask you this: what is WGS83? Is that the predecessor to WGS84? If so, is there a converter for that?

No, actually it's too far South.

Let me ask you this: what is WGS83? Is that the predecessor to WGS84? If so, is there a converter for that?

There is no WGS83. It's NAD83. And it's within a meter of WGS84 all over the continental US.

You seem to be missing the point of all the responses you hvae received in this thread: your problem is almost certainly NOT a datum problem. Unless there is significant information you have not told us. If the coords were taken with NAD27 it might (emphasize might) explain your issue.

But there is a wide range of other explanations for what you are seeing; miscalibration of Google Maps, a jetty or pier that is not shown in the maps, misunderstanding of the coordinate format on your part, etc.

Your continued attempt to explain the difference in terms of datum shifts is more than a little puzzling to me, since I thought I was exceedingly clear in my response.

If your point is falling out in the ocean in Google Maps, most likely the cause is your input is being interpreted as an East Longitude. Try the same input, with a negative longitude to signify West longitude. This input works ( 45 15.221' N 122 12.258' W ) as well as ( 45 15.221' -122 12.258' )

Hi,

I have been using the negative longitude.

It's not hugely off. The location should be somewhere in Rhode Island, and Google Maps shows it just south of Block Island, in the water.

I was hoping that the difference in WGS84 before and after the upgrade would be enough to put me on dry ground.

Are you sure you have the correct decimal place for Latitude? N41 49.440 is the center of Providence, RI, but N41 4.944 is just south of Block Island.

There is no WGS83. It's NAD83.

Your continued attempt to explain the difference in terms of datum shifts is more than a little puzzling to me, since I thought I was exceedingly clear in my response.

Yes, perhaps I should be a little clearer as to the problem.

I'm trying to solve a puzzle. This puzzle was written in 2003 and as yet nobody has solved it. It is somewhere in RI and that's all anybody knows. The clue page has a little geography quiz with very simple questions such as "The Sunshine State."

He tells you that the coordinates of the box you're trying to find are N41 ab.cd and W71 ef.gh, in degrees and minutes, using WGS 84.

Based on your answers to the simple questions, you're supposed to count a certain number of characters in each answer and use that to look up a digit, which you substitute for a, b, c, and d.

Everybody has the same problem: they get a point in the ocean just south of RI.

The person who created this puzzle is known for putting in little tricks and twists. When I read that that there was a 2004 upgrade, I thought I had the solution as to why nobody has found it.

Incidentally, I did see a reference to WGS83, which is why I asked about it:

Yes, perhaps I should be a little clearer as to the problem.

He tells you that the coordinates of the box you're trying to find are N41 ab.cd and W71 ef.gh, in degrees and minutes, using WGS 84.

Based on your answers to the simple questions, you're supposed to count a certain number of characters in each answer and use that to look up a digit, which you substitute for a, b, c, and d.

Everybody has the same problem: they get a point in the ocean just south of RI.

Is the value of c greater than 5? If not, perhaps he actually used DD MM SS, which sort of makes sense in this context. If it is, then another issue is the precision of his coordinates: .01 minutes in latitude translates to about 60 feet.

as Fizzy says, it could be a bunch of different causes and is most likely not a datum issue if it is more then a couple hundred feet from the expected location.

Is is a published cache? what is the GC number? That will make it easier to figure out what's going on.

Is is a published cache? what is the GC number? That will make it easier to figure out what's going on.

Here is the webpage:

http://www.mapsurfer.com/boxes/box83.html

What I get is about 10 km from land.

The first 5 questions are very easy. The last 3 are a little trickier, but even so, there's no possible answer to these that would put you on land, given the answers to the first 5.

There must be some kind of a trick involved, but trying to figure it out is the hard part.

Even using minutes and seconds puts in around the same place.

Edited by honeybearclan

Looks like fun puzzle.

I guess we shouldn't discuss the solution of a Letterbox here either, sort of in fairness to them, quid pro quo wise!

But we can investigate the nature of the error. I suspect it's a puzzle type 'trap' for the unwary.

edit: First run landed in the ocean as well, but I think I see a bigger problem with the puzzle.

It might be a small typo or simply a logic 'twist'. Thinking!

edit: Puzzle discussion now for me now in email.

Doug 7rxc

Edited by 7rxc

The most common typo is probably transposed numbers. See if switching a couple makes sense.

Incidentally, I did see a reference to WGS83, which is why I asked about it:

Yeah, that's wrong. Must have meant NAD83.

The most common typo is probably transposed numbers. See if switching a couple makes sense.

Incidentally, I did see a reference to WGS83, which is why I asked about it:

Yeah, that's wrong. Must have meant NAD83.

I agree on the typo or transposition problem, there are some other things about some of the questions as well.

Fortunately, I'm not the one hunting for it... but I like puzzles. Trying to reconcile possibilities with the questions and

As for the WGS83, you are correct. Unless someone decided to coin a term for what happened when the FIRST NAD83 was tweaked to be the current NAD83... very minor correction done when WGS84 was presented. Now they match up better. Think that was less than a half metre in both axes.. total. Would have to look that up. By comparison, the new updates to WGS datum will be miniscule. The big one was from NAD27 to NAD83. Over 200m N/S and 10m E/W or so locally here. Depended on where you were on the globe. That was the jump from standard survey techniques to modern digital methods.

Mostly moved the center reference of the Earth a bit. Believe they use center of mass now for the orbital mechanics. Could be wrong.

Doug 7rxc

Edited by 7rxc

Don't want to get back on the discussion of the puzzle, but I believe I solved it! At very least I found the 'twist' of logic.

hbclan check your email... or contact me. It is NOT GPS related in any way! Just logical and deceptive. Fun!

Doug 7rxc

Must....be......strong.....

But don't leave town.

Must....be......strong.....

But don't leave town.

Read away, I didn't tell you what I found, just asked how far you want to go with assistance!

No guarantees anyway, since I have no way to verify it, but it looks good!

Doug 7rxc

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