Expect larger Errors.

[Wise Old Owl]

http://i250.photobucket.com/albums/gg275/MarkSwarbrick/border.jpg


It appears all over the place while I was playing with several GPS systems. The border stones of the Mason Dixon line over the years have been replaced and don't expect accuracies of 16 foot when the maps and Google Earth are off by 275 feet! I discovered the error while looking for the cave (http://www.caves.org/grotto/cccc/Cave_DE.html) in Delaware some supposed 60 feet from the border. So don't expect some lines on the maps to line up exactly.

[Tin Man]

I followed the GPS in my truck today... drove right up someone's drive and across a faint lane to the adjoining road. :)

[beakerman]

That's ok a few years ago when I was in Louisiana I was driving across teh river on 310. I know I was on a bridge because I could breathe but according to all the GPS mapping software I was driving on water...the bridge was almost half a mile up river from me...now that is not a trivial error. I've seen it since then with other locations taht are easy to pinpoint on the map like intersections and such too.

[Old Grouse]

So, ah, what you're all saying is that you still have to use your wits despite the promise of electronic perfection?

[Great White]

I have observed similar issues as well. The problem is the data may not have been originally gathered by GPS. In fact, digitized maps are the usual source. Errors always appear. The lines look great on a the original 1:25000 or 1:50000 map but when you go into the real world they are off by a few hundred meters. Don't forget about GPS errors as well.

Maps, either paper or digital, are only an abstraction of the real world. They will never have a scale of 1:1.

I remember my father once examined a USGS topo map and found a large river that was missing in one map edition but later reappeared in a newer edition.

[Tin Man]

So, ah, what you're all saying is that you still have to use your wits despite the promise of electronic perfection?

some need a little more help...

http://blindhiker.com/

[beakerman]

So, ah, what you're all saying is that you still have to use your wits despite the promise of electronic perfection?

Yed unfortunately folks are relying on the accuracy of the technology rather than acutally taking a look at what is happening.

This is something I have been noticing for some time and it came to a head with me just 2 weeks ago when I was doing th orienteering event at our district camporee....i had Eagle scouts that could not orient a topographic map nor could they take a simple bearing on the map or inthe real world.

[Tin Man]

Yed unfortunately folks are relying on the accuracy of the technology rather than acutally taking a look at what is happening.

This is something I have been noticing for some time and it came to a head with me just 2 weeks ago when I was doing th orienteering event at our district camporee....i had Eagle scouts that could not orient a topographic map nor could they take a simple bearing on the map or inthe real world.

I helped our troop run an orienteering event at the Klondike this year. Hopefully, a few learned how to use a map and compass and will do better at the Fall Camporee where we will be doing this again. Many want to teach gps and I argue there really is nothing to teach except how to check with a map and compass which rarely need a change of batteries. :)

[beakerman]

I helped our troop run an orienteering event at the Klondike this year. Hopefully, a few learned how to use a map and compass and will do better at the Fall Camporee where we will be doing this again. Many want to teach gps and I argue there really is nothing to teach except how to check with a map and compass which rarely need a change of batteries. :)

Yeah I was really embarrassed for the Eagles but I had leaders that failed too. Maybe I was too hard on them but I learned this stuff when I was 10-11 years old why can't they?

I'm refocusing our troops orienteering on topographic maps...I found that my predecessor just used road maps. So much for even attempting to take into account elevation changes...:rolleyes:

[Wise Old Owl]

Well don't be too hard on them.... Those Eagles need practice, practice...

Hey pit the Adults vs the Eagles!

[Wise Old Owl]

Anybody else see big errors on this equipment?

[ki0eh]

I've seen topo maps stored in the Garmin GPS be off by 100 meters or have really old road base info, like 30 years out of date. No map is perfect. Any map, like any other human created communication, needs to be used critically. Just like postings on an Internet forum. :D

[hellomolly]

http://maps.google.com/maps?hl=en&q=new+york&um=1&ie=UTF-8&hq=&hnear=New+York,+NY&gl=us&ei=S7LZS6yPM4KC8gbBwPhG&sa=X&oi=geocode_result&ct=image&resnum=1&ved=0CBIQ8gEwAA (http://maps.google.com/maps?hl=en&q=new+york&um=1&ie=UTF-8&hq=&hnear=New+York,+NY&gl=us&ei=S7LZS6yPM4KC8gbBwPhG&sa=X&oi=geocode_result&ct=image&resnum=1&ved=0CBIQ8gEwAA)

My favorite: Direction #46: Kayak across the Pacific Ocean, 3,879 miles.

:eek: :banana

[garlic08]

A lot of areas, especially out West, were surveyed "from the bar".

There's also a real basic problem with projecting a round surface onto flat square paper. There has to be an error somewhere.

Coordinate systems have changed over the years, too. Look in the GPS menu--NAD27 or WGS84? You need to pick the right one for your map. That has caused some issues for me before.

[Two Speed]

A lot of areas, especially out West, were surveyed "from the bar".Out west wasn't the only place that occurred. The Pine Barrens (http://en.wikipedia.org/wiki/Pine_Barrens_speculation) scandal in Georgia is one I'm aware of.
There's also a real basic problem with projecting a round surface onto flat square paper. There has to be an error somewhere.Gonna second that.
Coordinate systems have changed over the years, too. Look in the GPS menu--NAD27 or WGS84? You need to pick the right one for your map. That has caused some issues for me before.Even better, the current geoid is constantly being updated, so there will always be some "wiggle" in the data.

Really, the question is will the equipment you're using, be it map & compass, GPS, Ouija board, whatever, get you close enough to your destination that you can work it out?

[Connie]

I was at Champoeg State Park, Oregon, for a day, and saw Scouts doing an orienteering course. After the event, I met the lady orienteering instructor, from a reasonably local orienteering organization, that was asked to help lay out the course for the event.

I wish I remember the name. I do have the brochure, somewhere around here.

I mentioned this, because orienteering groups put on events and these people would be a good resource for helping get instruction to the scouts and other groups. Maybe attend one of their events, after a little "orientation" of course.

I couldn't resist!

[myotheralt]

I helped our troop run an orienteering event at the Klondike this year. Hopefully, a few learned how to use a map and compass and will do better at the Fall Camporee where we will be doing this again. Many want to teach gps and I argue there really is nothing to teach except how to check with a map and compass which rarely need a change of batteries. :)

I had the batteries die on a map once. It was horrible, I couldn't unfold it or anything! :-?

[Wise Old Owl]

Uhh yea but my map doesn't burn,,,,

[Buzz_Lightfoot]

http://maps.google.com/maps?hl=en&q=new+york&um=1&ie=UTF-8&hq=&hnear=New+York,+NY&gl=us&ei=S7LZS6yPM4KC8gbBwPhG&sa=X&oi=geocode_result&ct=image&resnum=1&ved=0CBIQ8gEwAA (http://maps.google.com/maps?hl=en&q=new+york&um=1&ie=UTF-8&hq=&hnear=New+York,+NY&gl=us&ei=S7LZS6yPM4KC8gbBwPhG&sa=X&oi=geocode_result&ct=image&resnum=1&ved=0CBIQ8gEwAA)

My favorite: Direction #46: Kayak across the Pacific Ocean, 3,879 miles.

:eek: :banana

Heheh.....9417

Darn, came out too small. Google driving directions from Tokyo to New York.

[lilricky]

Just a question, when you guys experience these errors with your GPS's, how many satellites are connected to you? You do know that depending on the time of day, obstacles like buildings,trees, mountains,etc, and weather conditions, the accuracy of your device can be anywhere from 10 feet to over a mile. Just something to think about. GPS devices are not 100% accurate at all times, nor are they designed to be.

[Wise Old Owl]

Damn - good question, it doesn't matter, I have had three to get a 60 foot error or 4 to get a 30 foot with altitude and that whole thing with advanced sat with data correction clearly doesn't work.... until they launch one in a geosynchronous orbit over Wichita. There could be ten, and the error can be less than ten feet. The units have to see past the solar noise and terrain and calculate from a circular digital transmission pattern a solution to your location.... No I didn't make that up. I still wonder if the data error has been turned off how do the smart bomb land on the targets?

N3GWD.

[Helios]

I love it when my GPS just says "driving on road" and has no idea where I am. I just thought I had a lazy model that gave up after a few turns from major roads. :-)

[Wise Old Owl]

Joe change the settings from shortest route to fastest route... you can do it.

[RockDoc]

As a former USGS employee (geologic division, not mapping division) I can say that such errors are rare (and rapidly fixed). The quad map series is, or should I say was, remarkable in its accuracy for something that (back in the day) was made by humans sitting at tables looking at stereo photos. A lot of energy was spent field checking and regularly updating each map as well.

In contrast, a common rationale for computer based maps, including GPS, is that money spent on field work can be saved. So ground truthing is a thing of the past (even on big dollar projects). The philosophy is that as long as the map is bleeping beautiful it must be accurate. :rolleyes:
Of course that idea is false, but the public is pretty gullible as long as the product looks good.
Making crap look good is how the Chinese got rich, isn't it?




I remember my father once examined a USGS topo map and found a large river that was missing in one map edition but later reappeared in a newer edition.

[4eyedbuzzard]

I've found GPS receivers to be exceedingly accurate. Most surprising is how accurate my golf GPS is - generally within 1 yard of LASER measurements. A friend of mine has an airplane, and he's also found GPS accuracy generally to be with a meter or so (and lets hope so because most all precision instrument approaches are made using GPS). With auto GPS units, the "snap to road" mode most use probably affects their perceived accuracy more than the true error present.

I think a lot of maps need updating.

[Odd Man Out]

I'm thinking of the episode of "The Office" where Michael drove his car into a lake because the GPS told him to.:p

[Wise Old Owl]

I'm thinking of the episode of "The Office" where Michael drove his car into a lake because the GPS told him to.:p


http://www.youtube.com/watch?v=0yyKrS8jwSY