My "location" is still WAY off

[BowerBunch]

I posted a message a while back about my "location" being way off. The map display shows me about 500 ft east of where I know I really am.

 

I got several suggestions from people and I STILL am way off.

 

Questions:

 

1) Is it possible for a unit to be bad and show it in this manner?

 

2) One person referenced "map datum". a) I tried several in setup with no change, I haven't found any good explanation of "map datum", c) I would assume the software that I also got (from Magellan) uses the same datum out of the box as the GPS.

 

But given those assumptions, things didn't change. And I could never find out from Streets and Destination what datum they are using.

 

3)

 

Anybody else got any suggestions?

 

As you might imagine, this is getting very frustrating. In one cache I located, I was right on it (0 feet) and there it was. The next cache I didn't find but I don't know if it is because I am blind and didn't see it or is it 500 feet west of me. How would I know if it is unpredictable?

 

 

HELP!!!!

 

(whimper, whimper, whimper).

 

Michael Bower

bowerbunch

[+Alan2]

Imagine map datum as a language. If someone gives you a word in French, you have to have your computer set to French before you enter the word or it won't work. If they give you a word in Swahili, your computer must be set to Swahili.

 

So, with GPS's, you must make sure that your GPS is set to the same language as the language used for the coordinates Datum and Format that you are getting. For example, the Format language on the cache pages is WGS84. So make sure your GPS is set for WGS84 BEFORE you enter the coordinates.

 

Now coordinates. These too must be handled the same way. You must match the Format. The web page lists the coordinates of the cache location in degrees and minutes and thousanths of minutes Format such as W41 34.276 Make sure your GPS is set to the same format and NOT to degrees/minutes/seconds or degrees/decimal degrees or some other Format.

 

If you mismatch Datums or coordinates, you will be off from the location you want.

 

Since you apparently was right on a cache once, you must be doing something right. Just do whatever it was you did again.

 

Alan

[+Alan2]

Imagine map datum as a language. If someone gives you a word in French, you have to have your computer set to French before you enter the word or it won't work. If they give you a word in Swahili, your computer must be set to Swahili.

 

So, with GPS's, you must make sure that your GPS is set to the same language as the language used for the coordinates Datum and Format that you are getting. For example, the Format language on the cache pages is WGS84. So make sure your GPS is set for WGS84 BEFORE you enter the coordinates.

 

Now coordinates. These too must be handled the same way. You must match the Format. The web page lists the coordinates of the cache location in degrees and minutes and thousanths of minutes Format such as W41 34.276 Make sure your GPS is set to the same format and NOT to degrees/minutes/seconds or degrees/decimal degrees or some other Format.

 

If you mismatch Datums or coordinates, you will be off from the location you want.

 

Since you apparently was right on a cache once, you must be doing something right. Just do whatever it was you did again.

 

Alan

[+Alan2]

quote:

---

Originally posted by Alan2:.. For example, the Format language on the cache pages is WGS84. So make sure your GPS is set for WGS84 BEFORE you enter the coordinates.

---

 

I should have said Datum not Format in this sentence.

 

One final note. You might be setting everything right. Just couldn't find the cache. Keep trying. I you're still running into problems, try contactoing a local cacher who can go out with you and show you the ropes.

 

Alan

[+Criminal]

Your location is off in relation to what? Are you saying the spot on which you are physically standing is not coinciding with the spot the on the map your GPSr is showing you? If so, I have noticed the maps in my old III+ were inaccurate in certain areas. There’s a whole section of SR16 that’s missing in the built in maps My V must have newer maps.

 

If you have access to a mapping program like “Streets and Trips” you can record the coordinates from your GPSr at the location in question, and then go home and transfer them into the mapping program and see where it puts you.

 

If I completely misunderstood your problem I apologize.

 

If your house catches afire, and there aint no water around,

If your house catches afire, and there aint no water around,

Throw your jelly out the window; let the dog-gone shack burn down.

**Huddie Ledbetter**

[+TeamJiffy]

One thing to find out is if your GPS unit can accurately show where you are.

 

Most GPS units have the ability to show where you are on a map built into the unit - it may not have every street (probably won't) but it will have some major streets in your area.

 

Pan your map in your unit, to find an intersection close to where you live where you feel you can safely get out of your car and stand at a safe corner of the intersection.

 

Then, turn on your GPS unit, get a lock, and then see if your map shows you at the intersection. Zoom in to the tightest zoom.

 

Certainly a 500 foot error would show up.

 

If your GPS receiver shows you at the right place, then you may be doing something wrong. Most GPS units want their 'datum' to be set to WGS84, to match the web site, and you want to have your GPS display and enter data in the 'dd mm.mmm' format (degree/minute format).

 

One thing I had to learn myself: Don't make it too complicated! Just put your GPS unit in WGS84 datum, degree/minute format (dd mm.mmm), and enter the latitude/longitude given on the web page, exactly as shown. In other words, don't make the mistakes I first made!

[+TeamJiffy]

One thing to find out is if your GPS unit can accurately show where you are.

 

Most GPS units have the ability to show where you are on a map built into the unit - it may not have every street (probably won't) but it will have some major streets in your area.

 

Pan your map in your unit, to find an intersection close to where you live where you feel you can safely get out of your car and stand at a safe corner of the intersection.

 

Then, turn on your GPS unit, get a lock, and then see if your map shows you at the intersection. Zoom in to the tightest zoom.

 

Certainly a 500 foot error would show up.

 

If your GPS receiver shows you at the right place, then you may be doing something wrong. Most GPS units want their 'datum' to be set to WGS84, to match the web site, and you want to have your GPS display and enter data in the 'dd mm.mmm' format (degree/minute format).

 

One thing I had to learn myself: Don't make it too complicated! Just put your GPS unit in WGS84 datum, degree/minute format (dd mm.mmm), and enter the latitude/longitude given on the web page, exactly as shown. In other words, don't make the mistakes I first made!

[+apersson850]

Accuracy of the bas map, built in to the unit, may not be that good, that it accurately can tell you which street crossing you are at, even if the street crossing is on the map.

 

How about comparing with another GPS, where the user is sure about how to handle it? Assuming it's a set-up mistake, that is.

 

Anders

[+Dan_Edwards]

Here is a example. If I am standing in front of my house, where two streets meet, all of the GPS maps I have show me about 250 feet up one of the streets. This is pretty consistant with all maps I have found on my Palm, the PC, or online. It is consistent even with different makers of software, Microsoft Streets and Trips, does the exact same thing as Delorme products. If I ask Yahoo or other online maps where is my address, it points to about 250 feet up the same street.

 

Maps are only as good as the people who enter the data. The map data is also heavily compressed in most cases. Many contain errors from years back that were never corrected because until GPS became accurate just two years ago it was a pain.

 

Delorme is calling the current 2003 update to Street Atlas the most significant update in 10 years. This is because they can now use sat photos and other means to quickly verify streets. It may just be marketing hype, but with accurate GPS readings available I would expect a huge growth in accuracy in the next few years.

 

I would find someone else, or a store and verify that it's not just your unit, but I would be shocked to find out that it was just your unit.

 

A = A

[BowerBunch]

Couple of comments back on all of your posts:

 

1) Finding the cache I couldn't find: My georookie friend found the cache that I couldn't and he was using my GPS. SO I assume my GPS is pointing in the right place. But I will NOT go back to that cache without him. (I've been three times and got stung by three bees. He went twice and found it and didn't get stung. So I'm sticking with HIS luck.)

 

2) About the GPS knowing where I'm at and me knowing where I'm at. The place where I notice the error is at my house. I can see my street on the GPS map, I can see the cross street. I know where my house is on those streets. But the GPS shows me east by about 500 ft according to the scale on the GPS. I can try other streets and locations by walking around. But I still don't have a clue as to why it does this.

 

I'll try some of the ideas above but have done so in a slightly different way. (I think I can find a street to stand in the middle of .)

 

bowerbunch

[+Alan2]

Dan: I was very disappointed with 2003. My house is more off (by about 400 feet) than all my other map programs (Mapsource Topo, Metroguide and Roads and Recreation). When I use 2003 to route and transferred it to my Vista, the route was telling me to turn in some cases a block before or afterwards. I went down the wrong street. However, this apears to depend on location. Some streets and towns seem more accurate than others. It's a nice program for someone not using a GPS as the facilities of marking, the 6 million POI's, and the turn by turn printouts are impressive. They also have verbal direction if you hook up to your laptop and will take verbal commands from you like "What's my next turn?" Bottom line for my use however was I decided to get Metroguide to route, find street addresses and POI's and am now using that i conjunction with R+R and Topo. 2003 is now sitting in my drawer.

 

Alan

[+Alan2]

I dsouble check some of my figure with 2003 and the footage is not of that much, maybe 100-15-. But the problem I had was the routing not giving info at the right time on the right block. Da, I did check a typical intersection in Fort Collins and it was on within 50 feet so maybe it's just me.

 

Alan

[+Stunod]

My Meridian Platinum's maps are not perfect, either. There are a couple of highways that I drive and my GPS consistantly insists that I am 4-wheeling a parallel path a few hundred feet off. No big deal once you learn to accept it.

[BowerBunch]

It sounds like my GPS is telling me I'm where I am but that my map is telling me something else.

 

So the GPS is accurate but the map is not.

 

Well, ok, that means (I guess) that I will be able to find caches because I'm not dependent on a street in most cases.

 

But IF I'm trying to use it to get somewhere via driving, I may or may not find it.

 

Since the main purpose is the geocaching (what a great excuse to buy new toys ), I can live with this portion of it.

 

But we have to "accept" it. I don't think we should have to accept it. I realize it is based on somebody's input but we are living in a high tech society now, folks. Let's be more pro-active about getting accuracy.

 

(I'm sorry I'm getting on my high-horse about this but accuracy is important. Just not many people believe me. But imagine your doctor who is supposed to remove your appendix and removes your liver instead. How are you going to feel about it if his attitude is "whatever".)

 

Ok, I feel better now. I'm not happy with my unit but if they are all this inaccurate, what can I do?

[+apersson850]

If I download the MapSource WorldMap to my Vista, I get something like what you see. I was walking on one of the enbankements of the river Seine in Paris, but the WorldMap said it was the other one!

 

When comparing the stored track against MetroGuide Europe (when that became available), it told me I was on the side of the river, which I actually was.

 

Downloading MetroGuide maps to my Vista makes a lot of difference. I haven't compared them to the basemap, though, since I haven't been where the base map has coverage.

 

Anders

[JDMC]

Why don't you use USAPhotoMaps to verify your GPS accuracy? The aerial photos it uses are amazingly accurate as to lat/lon.

[MACpa]

Try this! take the latitude/longitude displayed on your GPS for your home. Go to one of the Satelite photo type pages on the web, Lost outdoors.com etc.,

I use USA photo maps it is a free downloadable program From JDMcox software. see where that program puts the spot. if it is on your house you know your GPS is correct.

If the inaccuracy of the maps upset you so much get off your high horse and re-map the entire country for us useing GPS technology not the outdated stuff that they used to create the maps we have now humans, with a stick and a note pad.

[BowerBunch]

Ok, MACpa, I get the point. I guess I was getting a little carried away with something that is supposed to be FUN. (Which it is.)

 

So how many sticky notes and pens do you think I will need to re-map the whole country.

 

There is a project for SETI where SETI uses massive amounts of computing by "borrowing" peoples machines when they are idle. SOrt of spreads the work.

 

Now if we could get ALL the people who have GPSs to help on this project.......

 

Thanks for the reality check, MACpa. I did need it.

 

I'll try your ideas later tonight and see what I find.

 

Again, thanks.

 

bowerbunch

[MACpa]

Let us know how you make out!

This SETI sounds like a good Idea I'm Glad you thought of it.

It bugs me too that I see the curser of my GPS in my neighbors yard. But When you look at the maps and see a 90* turn where there is only a gentle bend in the road you know someone did the best they could with the materials and equipment made available to them. I was relieved to find that in the modern satelite photo programs my $500.00 investment in GPS and accessories was not a waste.

[+Criminal]

Very often the owner of a database will intentionally insert “bad” data as a way of determining if a competitor has simply copied (stolen) their information. Let’s say I have a list of 20,000 radio frequencies with detailed info about each one. Someone buys my list and simply copies it to re-sell. How do I know he did such a despicable thing? I have inserted a few fake freqs complete with fake info. If the data in his list is the same as mine, then I know it was stolen and can pursue it through the legal system for copyright infringement. It would take as much effort for him to find my fakes as it would be for him to do the research and come up with his own list. That’s the theory anyway.

 

I don’t know if it’s the same for the owner of the map data but it’s certainly a possibility. There’s always the chance your house was a fake. If so, you have nothing to complain about right?

 

If your house catches afire, and there aint no water around,

If your house catches afire, and there aint no water around,

Throw your jelly out the window; let the dog-gone shack burn down.

**Huddie Ledbetter**

[+Criminal]

Very often the owner of a database will intentionally insert “bad” data as a way of determining if a competitor has simply copied (stolen) their information. Let’s say I have a list of 20,000 radio frequencies with detailed info about each one. Someone buys my list and simply copies it to re-sell. How do I know he did such a despicable thing? I have inserted a few fake freqs complete with fake info. If the data in his list is the same as mine, then I know it was stolen and can pursue it through the legal system for copyright infringement. It would take as much effort for him to find my fakes as it would be for him to do the research and come up with his own list. That’s the theory anyway.

 

I don’t know if it’s the same for the owner of the map data but it’s certainly a possibility. There’s always the chance your house was a fake. If so, you have nothing to complain about right?

 

If your house catches afire, and there aint no water around,

If your house catches afire, and there aint no water around,

Throw your jelly out the window; let the dog-gone shack burn down.

**Huddie Ledbetter**

[+Searching_ut]

In many areas Garmins maps display maps positioned wrong by a great deal. For instance, Metroguide maps are derived from the Tele Atlas database. They claim an accuracy of 12 meters or less for 70 percent of their data. The other 30 percent, mostly rural areas is data from Census bureau tiger map database, which is notoriously inaccurate. All the streets in my area are misplaced by more than 350 feet in a southwesterly direction. Many other areas are even more positionally incorrect.

 

Because the road maps are so inaccurate in the areas I primarily navigate through, I’ve pretty much given up on GPS for my vehicle navigation. The thing often doesn’t tell me about a turn till I’ve passed it, and the lock to road function will often lock to the wrong road. I primarily just use GPS in my boat, and for handheld use with TOPO maps.

 

Your mileage will vary greatly depending on where you are.

 

Jeff

[Adventureguy]

So, reading all of this thread seems to beg another question... How well do the GPSr's work with the topographic map software (Mapsource TOPO, Mapsend, etc)? Personally, I have no real use for metroguide (or the like from other manufacturers), but I'm certainly planning to get some uploadable topographic maps to go with whichever new GPSr I ultimatley buy... However, an error of 500' on a topographic map could be a really bad thing (one side of a canyon or the other, etc.). Obviously with any technology the user has to be prepared to use some common sense, and this certainly applies to a handheld unit designed to tell you exactly where you are anywhere in the world! But, still, if the TOPO maps are off by a few hundred feet consistently, then I see no reason to shell out the money for them instead of just using USGS paper maps in conjunction with the GPSr.

 

Any thoughts? Have you guys used the topographic map programs in your GPS's? Which company (Magellan, Garmin, etc.) has the best topographic maps that can be uploaded to their receivers?

 

Thanks, all !!!

[+Alan2]

Garmin's Maprsource Topo is 1:100,000 scale. I find it helpful in conjuction with printout I do from Topozone on the web page or my National Geographic Topo both of which are USGS 24000 scale. I don't do any real hiking but if I did I would definitely take along the 24000 quad maps. Mapsource Topo is good for general locationing , pointing out off roads roads in the woods and local parks so it aids in finding the best way to caches. But take paper maps for serious hiking.

 

Good luck

 

Alan

[+Alan2]

I forgot. Mapsource is the only maps you can load in Garmin GPS (same for each of the other manufacturers). Oncec in the GPS the topo map will help show your exact location of the paper quad 24000 scale map so you use both maps as companions.

 

Alan

[+Searching_ut]

The actual geographic data, and even road data on Garmins TOPO is a lot better than the R&R, or Metroguide road data. It comes from the USGS 1:100,000 scale USGS metric topo maps (That's why the contour lines are at strange intervals). The data is pretty old, but terrain doesn't tend to change much. It doesn't have a lot of current roads on it in some areas though due to the age of the database it comes from. POI data (The names listed in blue) however is often not as accurate as the contour lines etc., hence where it shows mountain peaks springs and stuff like that can be incorrect from time to time.

 

I've also got Magellans TOPO. I'm not sure where the terrain data comes from, but it seems fairly accurate, although it's not as detailed as Garmins TOPO. It's Missing many streams, springs, etc. The road data on the Magellan TOPO is definately TIGER map data, which as previously discussed is prone to error. It is however a lot more modern database, and thus shows a lot of roads that you won't find on Garmins TOPO.

 

Of the other products I own, I prefer National geographics TOPO state series. Very well indexed 1:24,000 scale USGS maps, which are the only way to go for hiking in my opinion. I also use expert GPS which will download TOPO, or aerial photos from terraserver if they're available for your area. I always print a map from one of these two programs if I don't actually have a USGS quad for the area I'm going into. I just use the GPS maps for general reference. It's wise to have a mechanical backup anyway.

 

None of the products is very up to date or accurate for trail data in many areas, hence you get to explore a lot of the time.

 

Hope this helps

 

Jeff