GPS accuracy question

[maxxkatt]

I use commander compass lite on my iPhone. It seems to only be accurate between 15 to 20 feet. This is find for finding hold home sites on google earth, but not so good on finding the corners of the house or other structures.

Is this due to commander compass lite or just our access to GPS in general?

Don't get me wrong, finding the home site within 15 - 20 feet is enough, I can do the rest by looking at my finds and seeing if they are the typical finds and trash to expect from that home site for that time period. Just wondering about the accuracy question.

 

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[hvacker]

I've never used a phone app but my understanding, like many things, you get what's paid for.
Surveyors equipment is very accurate but hauling it around is another problem.
Stand alone devices tell how close they will get. My only experience is with a Garmin but I haven't needed to test it's proximity.

 

[Electricfrontporch]

Some days you may get closer but that's pretty average for GPS.
They supposedly limit it for civilian use.
Survey equipment is more preside because it uses two separate units
and is able to triangulate more accurately.

Noah

 

[No gold in NY]

A smartphone is just a phone. Well, they do take pretty good pictures. If you need a GPS, get one. I use a Garmin 62s for geocaching. They can be very accurate, right down to 1-2 feet, but that depends on the hider and what they use. If it is a smart phone, I have found some of them to be 100 feet off at times.

 

[hvacker]

A smartphone is just a phone. Well, they do take pretty good pictures. If you need a GPS, get one. I use a Garmin 62s for geocaching. They can be very accurate, right down to 1-2 feet, but that depends on the hider and what they use. If it is a smart phone, I have found some of them to be 100 feet off at times.

That might make one wonder about other apps and accuracy. Finding out that a "ping" might not actually come from the closest tower has many implications when the Police use that information to prove a persons location.
There are many tech apps available that some rely very heavily on for the information to do hundreds of tests and conclusions. Using these apps to prove their conclusions have implications. An obvious question might be "Who's proving the apps?"
Along with this discrepancy of logic, many that use this phone information seem to have complete faith in what the app is telling them.
Some use phone info to fly planes?

 

[Charlie P. (NY)]

GPS.gov: GPS Accuracy

According to Uncle Sam your smartphone should be good to within a 16 ft radius

GPS can be refined. On our sailboat I had a dedicated Garmin GPS WAAS receiver/antenna and that was good to about a nine foot radius (15 years ago).

"REAL" surveying GPS carrier phase receivers are accurate to fractions of an inch.

 

[TerryC]

It used to be that they "detuned" the civilian side of the GPS receivers to be 10 meters off. They no longer do that. GPS receivers that pick up at least 12 sats will be only a couple/three feet off. But... you may be as much as 90 meters off if your GPS is set to the older NAD 27 standard and you use Google earth, which is set to the newer standard (NAD 83) WGS84. Most Topographical maps are still NAD 27 but in the lower left corner, they will post the NAD 83 difference. TTC

 

[TerryC]

Incidentally, NAD 27 is North American Datum 27 (1927). WGS 84 is World Geodetic System 84 (1984). The United States felt it had to "jump the gun" and be first. That is why it is not NAD 84! TTC

 

[boogeyman]

Some days you may get closer but that's pretty average for GPS.
They supposedly limit it for civilian use.
Survey equipment is more preside because it uses two separate units
and is able to triangulate more accurately.

Noah

I may be wrong, but last I heard they quit messing with the accuracy a ways back. I just changed over to a Garmin from years of Magellans. I think No Gold hit it with the statement "A smartphone is just a phone." If you're looking for inch & feet, bite the bullet and carry both. With the GPS you get or can get mapping pgms that do far more than the apps I've seen. An example would be saving your tracks to their own map and going back to where you left off to continue searching. And you can layer your map over GE or other maps. The new Garmin is way more accurate than my phone. So, hope that gives you a little help thinking which way you want to go. Oh, Another plus is with the mapping programs even the 20+ year old ones allow you can save your info to disk and the current map programs will read them.

 

[luvsdux]

I've found hand held GPS units to be accurate with in a few feet which is accurate enough for finding most sites, but not pinpoint for a small target.
luvsdux

 

[maxxkatt]

I was hunting a house site and a survey crew was on site. I ask them how accurate their equipment was and they said down to the inch or so. I can use compass commander on my iphone and mark my position and walk away 30 yards and use it to find my just marked position and it can be 10 - 15 off. But as said before if it gets me that close, I can use flowers and types of trees and finds to get pretty close to the hold home site. For instance an old long gone Church was easy to find because of Yucca plants and Cedar trees planted on both sides of the long gone church building. They planted the Yucca plant to ward off evil spirits and the cedar trees for long life. Of course finding Daffodils and other plants not common to the woods is a great tip off to an old home site along with old topo maps.

 

[TerryC]

I was hunting a house site and a survey crew was on site. I ask them how accurate their equipment was and they said down to the inch or so. I can use compass commander on my iphone and mark my position and walk away 30 yards and use it to find my just marked position and it can be 10 - 15 off. But as said before if it gets me that close, I can use flowers and types of trees and finds to get pretty close to the hold home site. For instance an old long gone Church was easy to find because of Yucca plants and Cedar trees planted on both sides of the long gone church building. They planted the Yucca plant to ward off evil spirits and the cedar trees for long life. Of course finding Daffodils and other plants not common to the woods is a great tip off to an old home site along with old topo maps.

One great feature of handheld GPS units is... if you use the same unit, it will return you to the same "mark" within a couple of feet (make sure you are using the WAAS function). Using separate units may not get you that close. Also, I very much agree with the foliage mention you make. It is surprising the number of long-lost dwellings that have been "re-found" simply by noticing the non-local plantings that were made! Good tip. TTC

 

[TerryC]

GPS.gov: GPS Accuracy

According to Uncle Sam your smartphone should be good to within a 16 ft radius

GPS can be refined. On our sailboat I had a dedicated Garmin GPS WAAS receiver/antenna and that was good to about a nine foot radius (15 years ago).

"REAL" surveying GPS carrier phase receivers are accurate to fractions of an inch.

Hey Charlie, When TimC and I Were prospecting around Stanton, AZ, we Latched up with a surveying person. She told us the current survey units were more accurate than the width of a gnat's hair. Impressive! TTC

 

[Charlie P. (NY)]

Technology is great stuff. At one time we were able to track submarines by the slight change in elevation of the ocean's surface above them. (I briefly worked on the LAMPS Mk II Project a long, long time ago when the Seahawk was shiney new).


I had a friend that worked at Lockheed and he wired my laptop, Garmin GPS/Chartplotter, Standard VHF, Raytheon ST-60 Wind, Depth & Speed and ST-4000 auto pilot all together with Cap'n chart plotting on the laptop; showing a little red icon on the display of our coordinates on the chart and heading. This was back in 2000.

I could set the boat to keep a constant wind heading or compass heading and it would automatically correct at pre-set waypoints. The VHF was in the chain because if I punched the "Distress" button it transmitted the coordinates as part of the signal - provided the receiving unit was DSC compatible.

You can do this off the shelf now, but he sat down with his laptop and actually looked at the output code and worked out a compatible format among all the various units to find one that they would all agree on. Without him I would never have been able to do it. Now they come ready to communicate wirelessly.

But you'd still better not rely on them. ;-) Uncle Sam can encode the GPS system any time they feel the need.

Now I have a catboat with a fixed magnetic compass, a hand bearing compass and a handheld VHF. Simplify, simplify.