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Hi

I wont start a long discussion what GPS device is the best but I do want to start a discussion about accuracy and response times. I was wonder if people here that owned devices from different companies felt A is more accurate than B or it takes A only 30 sec to find the satellites and 5 min for B.

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I wont start a long discussion what GPS device is the best but I do want to start a discussion about accuracy and response times. I was wonder if people here that owned devices from different companies felt A is more accurate than B or it takes A only 30 sec to find the satellites and 5 min for B.
Lets see... say that one was better than the other, but without saying we found it to be the best...hooboy... :laughing:

 

We've noticed that a GPSrs fix time and "accuracy" is dependant on the model age, not so much by brand.

Using all four phone OSs, we've noticed that in phones too.

- It's only as "accurate"/quick as the electronics inside allow it to be, which improves (sorta) each year.

 

Consumer-grade GPS on it's best day is only "accurate" to around 10', and most GPS today meets that.

Even my old 60cxs gets a fix inside the house...

Not sure why an extra minute or two in sat fix would be an issue.

We often cache in different areas (1 or 2 degrees), and so we usually have to wait another minute or so for our GPSrs to adjust. :o

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Hi

I wont start a long discussion what GPS device is the best but I do want to start a discussion about accuracy and response times. I was wonder if people here that owned devices from different companies felt A is more accurate than B or it takes A only 30 sec to find the satellites and 5 min for B.

 

I've been using a Garmin since the start - various models have become more accurate and faster at computing bearing and distance.

 

One feature I did disable was GLONASS. At some point I found it was seriously interfering with my readings and accuracy. Not sure if this was something the Russians did by intent or accident. Haven't re-enabled it.

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Another "task" one can easily forget to do is allowing the GPSr to actually /get a fix/ If your unit is turned off and you travel to a different location from the one in which the unit was on and being used, is to turn it on (in the new location) and WAIT a few extra minutes. While the sats might show you have then, there are internal updates the unit does to get a solid fix - One being to set the Current Location file

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Hi

I wont start a long discussion what GPS device is the best but I do want to start a discussion about accuracy and response times. I was wonder if people here that owned devices from different companies felt A is more accurate than B or it takes A only 30 sec to find the satellites and 5 min for B.

 

GPS fix happens before the application loads normally.

 

accuracy is normally +/- 10ft.

 

this has been the same with the last 7 or 8 devices i tried.

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GPS fix happens before the application loads normally.

 

 

You sure about that? My eTrex30 and GPSMAP 64s will boot up and display the map screen with a '?' on it where the current location (blue triangle) is, if it has not been turned on for a week or more and if it has changed it's position significantly since it was last turned on. They usually update the current position in another 10 seconds or so.

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GPS fix happens before the application loads normally.

 

 

You sure about that? My eTrex30 and GPSMAP 64s will boot up and display the map screen with a '?' on it where the current location (blue triangle) is, if it has not been turned on for a week or more and if it has changed it's position significantly since it was last turned on. They usually update the current position in another 10 seconds or so.

 

i turned on a Casio c811 that had been off for two weeks, 180 miles from its last location. it took about 10 seconds including the loading time of the app that was around five seconds. i turned on a galaxy rugby pro that was off for over a month, 170 miles from ITS last location, there was no noticeable difference between application load vs gps fix. neither has had a sim card in months. the s2 i turned on today hasn't been used in about a month, it it took two or three seconds to fix. the Kyocera I'm using now takes the longest, around five seconds to drop from +/-30 feet to +/-10 , after the application loads which is about five seconds.

 

i haven't seen > +/-17 feet in a long time, unless there is a lot of flat rock vertically.

 

it's fairly normal for the application loads to be longer than the gps fix, airplane mode doesn't seem to make a difference.

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an update, i finally found a section of trail that only achieved 33ft (60ft spread) accuracy. here is most of the track, color coded by accuracy.... blue is 10ft

green is 13-16

red is 33ft

 

picture or track:

Screenshot_2016_09_11_13_43_11.png

 

now, the phone was banging against the front wheel on the return, and you can see the earlier track was still VERY good by the color coding, maybe knocking about the front wheel isn't good for triangulation? who knew ? lol

 

anyway here are some more...

 

yes, there was tree cover and a little elevation change ;-)

2016_09_11_13_55_12.jpg

 

and of course that five minute period when the wheel did some pestering to the phone...

 

2016_09_11_13_47_52.jpg

 

all in all there were 6000 recorded points for 41 3/4 miles, thirty of them were 33ft accuracy, the rest between 13 and ten feet.

 

thanks locus team, this app is great!

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Time to first fix

The TTFF is commonly broken down into three more specific scenarios, as defined in the GPS equipment guide:

 

Cold or Factory: The receiver is missing, or has inaccurate estimates of, its position, velocity, the time, or the visibility of any of the GPS satellites. As such, the receiver must systematically search for all possible satellites. After acquiring a satellite signal, the receiver can begin to obtain approximate information on all the other satellites, called the almanac. This almanac is transmitted repeatedly over 12.5 minutes. Almanac data can be received from any of the GPS satellites and is considered valid for up to 180 days. Manufacturers typically claim the factory TTFF to be 15 minutes.

 

Warm or Normal: The receiver has estimates of the current time within 20 seconds, the current position within 100 kilometers, and its velocity within 25 m/s, and it has valid almanac data. It must acquire each satellite signal and obtain that satellite's detailed orbital information, called ephemeris data. Each satellite broadcasts its ephemeris data every 30 seconds, and is valid for up to four hours.

 

Hot or standby: The receiver has valid time, position, almanac, and ephemeris data, enabling a rapid acquisition of satellite signals. The time required of a receiver in this state to calculate a position fix may also be termed Time to Subsequent fix (TTSF)

 

Many receivers can use as many as twelve channels simultaneously, allowing quicker fixes.[1] Many cell phones reduce the time to first fix by using assisted GPS (aGPS): they acquire almanac and ephemeris data over a fast network connection from the cell phone operator rather than over the slow radio connection from the satellites.

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Time to first fix

The TTFF is commonly broken down into three more specific scenarios, as defined in the GPS equipment guide:

 

Cold or Factory: The receiver is missing, or has inaccurate estimates of, its position, velocity, the time, or the visibility of any of the GPS satellites. As such, the receiver must systematically search for all possible satellites. After acquiring a satellite signal, the receiver can begin to obtain approximate information on all the other satellites, called the almanac. This almanac is transmitted repeatedly over 12.5 minutes. Almanac data can be received from any of the GPS satellites and is considered valid for up to 180 days. Manufacturers typically claim the factory TTFF to be 15 minutes.

 

Warm or Normal: The receiver has estimates of the current time within 20 seconds, the current position within 100 kilometers, and its velocity within 25 m/s, and it has valid almanac data. It must acquire each satellite signal and obtain that satellite's detailed orbital information, called ephemeris data. Each satellite broadcasts its ephemeris data every 30 seconds, and is valid for up to four hours.

 

Hot or standby: The receiver has valid time, position, almanac, and ephemeris data, enabling a rapid acquisition of satellite signals. The time required of a receiver in this state to calculate a position fix may also be termed Time to Subsequent fix (TTSF)

 

Many receivers can use as many as twelve channels simultaneously, allowing quicker fixes.[1] Many cell phones reduce the time to first fix by using assisted GPS (aGPS): they acquire almanac and ephemeris data over a fast network connection from the cell phone operator rather than over the slow radio connection from the satellites.

 

I'm not sure if I missed something you meant to highlight, but it just looks like a block quote of text on my browser.

 

was there a specific point ? :-)

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I'm not sure if I missed something you meant to highlight, but it just looks like a block quote of text on my browser.

 

was there a specific point ? :-)

Yes, it clearly explains Time To First Fix (TTFF) that directly relates to the OP's question/discussion regarding GPS "accuracy and response times". It explains why some devices "appear" to have a faster TTFF and some tricks that can be used to speed up the TTFF. For good quality GPS measurements your receiver needs a copy of the almanac and the ephemeris data.

 

 

In the fields of science, engineering and statistics, the accuracy of a measurement system is the degree of closeness of measurements of a quantity to that quantity's true value.[1] The precision of a measurement system, related to reproducibility and repeatability, is the degree to which repeated measurements under unchanged conditions show the same results.[1][2] Although the two words precision and accuracy can be synonymous in colloquial use, they are deliberately contrasted in the context of the scientific method.

 

A measurement system can be accurate but not precise, precise but not accurate, neither, or both. For example, if an experiment contains a systematic error, then increasing the sample size generally increases precision but does not improve accuracy. The result would be a consistent yet inaccurate string of results from the flawed experiment. Eliminating the systematic error improves accuracy but does not change precision.

In context of the above definitions, you present some pictures that "appear" to show your phone provides precise data and you assume accurate (but that is not proven its assumed). However, it's a little disingenuous to try to illustrate 33' errors on a 2 mile scale where differences between the tracks are visually indistinguishable. Not to mention that the receiver built in "accuracy" measurements are normally estimates and are subject to a significant amount of manufactures "fudging" often just to "appear" to be the best.

 

It's just like cell phone signal strength measurements, where one phone shows 5 bars and one phone shows 2, where under the hood they are essentially the same value just "displayed" to an advantage.

 

How about uploading your raw data and letting us have a look. I also suggest that you survey in some existing survey monuments (with known coordinates) for a start of an accuracy assessment.

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I'm not sure if I missed something you meant to highlight, but it just looks like a block quote of text on my browser.

 

was there a specific point ? :-)

Yes, it clearly explains Time To First Fix (TTFF) that directly relates to the OP's question/discussion regarding GPS "accuracy and response times". It explains why some devices "appear" to have a faster TTFF and some tricks that can be used to speed up the TTFF. For good quality GPS measurements your receiver needs a copy of the almanac and the ephemeris data.

 

 

In the fields of science, engineering and statistics, the accuracy of a measurement system is the degree of closeness of measurements of a quantity to that quantity's true value.[1] The precision of a measurement system, related to reproducibility and repeatability, is the degree to which repeated measurements under unchanged conditions show the same results.[1][2] Although the two words precision and accuracy can be synonymous in colloquial use, they are deliberately contrasted in the context of the scientific method.

 

A measurement system can be accurate but not precise, precise but not accurate, neither, or both. For example, if an experiment contains a systematic error, then increasing the sample size generally increases precision but does not improve accuracy. The result would be a consistent yet inaccurate string of results from the flawed experiment. Eliminating the systematic error improves accuracy but does not change precision.

In context of the above definitions, you present some pictures that "appear" to show your phone provides precise data and you assume accurate (but that is not proven its assumed). However, it's a little disingenuous to try to illustrate 33' errors on a 2 mile scale where differences between the tracks are visually indistinguishable. Not to mention that the receiver built in "accuracy" measurements are normally estimates and are subject to a significant amount of manufactures "fudging" often just to "appear" to be the best.

 

It's just like cell phone signal strength measurements, where one phone shows 5 bars and one phone shows 2, where under the hood they are essentially the same value just "displayed" to an advantage.

 

How about uploading your raw data and letting us have a look. I also suggest that you survey in some existing survey monuments (with known coordinates) for a start of an accuracy assessment.

 

ahhhh, OK I see. thanks for an easily understood response.

 

that particular track will never be made public, it jest can't. :-)

 

the notion that an application might fake accuracy, or the might feed "altered" data to the application layers make perfectly good sense, and I agree it's totally possible. the problem with that theory is that when I take the same path more than once, the lines always fall into that 20-60 foot area, lending the possibility that it really is +-13feet as a norm. I wouldn't want to compare STREET tracks, since they are basically cheating with a nice big horizon, very few trees, and not likely to ever be a place that I will be hiking, let alone trying to find a cache or similar activity.

 

I've compared point data (yes from within the app) and it's consistent with the screen shots from above. honestly I would like to prove it wrong or poor, but each time I test by repeating a trail or locating a single point, it's the same results.

 

would you consider a street track , with open sky, fair game for analyzing?

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that particular track will never be made public, it jest can't. :-)

How about minusing the Nominal (lowest) Degree Lat and Nominal Degree Long from the data obfuscating your position but still preserving the data relationship. (For example if the positional data is Lat N12 34.567, just minus 12 degrees.)

 

I've compared point data (yes from within the app) and it's consistent with the screen shots from above. honestly I would like to prove it wrong or poor, but each time I test by repeating a trail or locating a single point, it's the same results.

In this case you really only test the repeatability of your device and without the raw data, no one can validate (or refute) your conclusions. As for controls I would be less concerned about open sky and more concerned with the cell network introducing any periodic or systemic errors or enhancements. I would do the test with the radio off. If you want to test the accuracy you need to test against a known baseline, either known survey markers/benchmarks or a post-processed DGPS solution of some form.

 

would you consider a street track , with open sky, fair game for analyzing?

Sure, if you want to repeat the data acquisition... How do you ensure your track is the same each time you do the route?

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that particular track will never be made public, it jest can't. :-)

How about minusing the Nominal (lowest) Degree Lat and Nominal Degree Long from the data obfuscating your position but still preserving the data relationship. (For example if the positional data is Lat N12 34.567, just minus 12 degrees.)

 

I've compared point data (yes from within the app) and it's consistent with the screen shots from above. honestly I would like to prove it wrong or poor, but each time I test by repeating a trail or locating a single point, it's the same results.

In this case you really only test the repeatability of your device and without the raw data, no one can validate (or refute) your conclusions. As for controls I would be less concerned about open sky and more concerned with the cell network introducing any periodic or systemic errors or enhancements. I would do the test with the radio off. If you want to test the accuracy you need to test against a known baseline, either known survey markers/benchmarks or a post-processed DGPS solution of some form.

 

would you consider a street track , with open sky, fair game for analyzing?

Sure, if you want to repeat the data acquisition... How do you ensure your track is the same each time you do the route?

 

Im fairly certain two things will happen if I change anything about the track points:

1 I'll screw it up

2 someone will call me a liar for having changed values (already happened, without changing anything)

 

I would prefer to just upload untouched racks, and let whoever wants to dissect them have at it.

 

I'm recording without Wi-Fi/cellular/Bluetooth/dlna/etc (aka airplane mode) most of the time already, but for these tracks, of course, no assistance from the evil towers of data.

 

I see what you mean about using a known survey marker, but I have no idea where to find them. decades ago I photographed a lot of them across the nation, but dumped those photos long ago. gotta list?

 

the only way I can guarantee I follow the same course while recording is to.... do it all the same. of course the points will be at different points along the route, so I think you might be hinting this is a poor way of gathering data? I'm game for whatever.

 

thanks for the guidance instead of instant criticism, it's refreshing :-)

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Im fairly certain two things will happen if I change anything about the track points:

1 I'll screw it up

2 someone will call me a liar for having changed values (already happened, without changing anything)

 

I would prefer to just upload untouched racks, and let whoever wants to dissect them have at it.

OK, fair enough (consider stop using it as an example though).

 

I'm recording without Wi-Fi/cellular/Bluetooth/dlna/etc (aka airplane mode) most of the time already, but for these tracks, of course, no assistance from the evil towers of data.

For any sort of quantitative and comparative analysis you need to control the experiment. With the radio on and off are valid test points as well, but if you are interested in GPS accuracy (vice device accuracy) then you have to use the same baseline.

 

I see what you mean about using a known survey marker, but I have no idea where to find them. decades ago I photographed a lot of them across the nation, but dumped those photos long ago. gotta list?

You can poke around the GC.com benchmarking areas and the NGS. I may endeavour to dig out some of my data buried in logs (I have potentially 140 points with a mix of phone and GPS) not a statistically significant amount but a start.

 

the only way I can guarantee I follow the same course while recording is to.... do it all the same. of course the points will be at different points along the route, so I think you might be hinting this is a poor way of gathering data? I'm game for whatever.

Track errors (not being on the same line for another test) just introduces additional error that gets hidden in the system error (your bike tracks may be better than you think). Tracking one edge of the sidewalk or the other may lessen biases in your data opposed to walking the sidewalk. If the track is uncontrolled the random errors will be attributed back to the device instead of the track.

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aha, I normally delete repeated (uneventful) track recordings, but these eight were still on the card.

 

speed varies between 25 and 65mph, for that section of the road. kind of neat to zoom in and see eight tracks from different days, almost in the same lane.

 

Screenshot_2016_09_13_18_47_55.png

 

anyway, I'll dig up some of those discs and see how bad a reading I can get. hopefully something useful.

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five phones. four of which do not have cellular service, and have not had their agps reset in.... a few weeks to a few months. i honestly don't know. the fifth phone was used to take the pictures and navigate to the disc.

 

i turned them on two at a time (or as fast as i could), started the app, and dropped them on the disc, then took a picture. yes, i neglected to change the formatting on one of the rugby's. oops. the point was to arrive, turn on, and drop the phones for a picture, as quickly as possible.

 

the results:

IMG_20160914_142619.jpg

 

for easy peasy reference, the green circle is 10ft radius, orange 20ft, red 30ft: (yes, i did this with the application)

Screenshot_2016_09_14_16_07_29.png

 

even easier, i drew a line to show distances:

Screenshot_2016_09_14_16_05_27.png

 

and easiest yet, a list of points, with the disc the first point in the list at zero and the other points listed by distance from the disc:

Screenshot_2016_09_14_16_08_07.png

 

i knew one of them was going to be eccentric, as it always has been. the '33footer' has been odd with dropping calls, dropping triangulation (yep still using the wrong word, thanks for noticing!) and dropping it's battery stats occasionally. keep in mind none of them were updated, allowed any connectivity, or given more time than it takes to turn on, start the app, and take a picture. the last one was actually loading the app as i focused the camera. i wanted to get hte worst possible reading i could.

 

i thought about using averaging, but didn't think that would be fair, since the sky was completely unobstructed, and i wasn't flying down a trail at 15-30mph, which i've called the 'normal' from my tracking comments.

 

by all means point out my mistakes, or go out and experiment for yourselves. i'm all ears. :)

Edited by ohgood
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these tests are proving very interesting. well, to me anyway, i notice it's getting pretty quiet. no biggie, carrying on! :-)

 

Green circle twenty ft radius

red and aqua ten ft radius

pink five ft radius

 

red points almost five year old c811 (Casio)

aqua points almost four year old rugby (Samsung)

 

i used my cheating application today, called GPS averaging. i let it run until it had calculated 100 times, then pulled the plug and dumped the pair of phones points into a directory, then drew the circles around them with locus.

 

apparently the Casio started off confused, and kept walking. the Samsung only got confused once, Ave was much tighter.

 

i still like the Casio better, idea display is easier to read and it's better in the hand.

 

next time I'll try near power lines and see if there are issues.

 

Pict tours:

Screenshot_2016_09_17_18_34_48.png

 

Screenshot_2016_09_17_18_35_01.png

 

Screenshot_2016_09_17_18_36_01.png

 

Screenshot_2016_09_17_18_37_07.png

 

thanks for tuning in, I'll try another tomorrow

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these tests are proving very interesting. well, to me anyway, i notice it's getting pretty quiet. no biggie, carrying on! :-)

 

1 that might be because nobody knows what conclusions you are drawing.

2 Are you claiming that phones under a clear sky converge quickly to the correct coords? I can't tell.

 

1 the conclusions were much earlier: that tree cover, sky conditions, didn't matter from my experiences.

 

2 clear sky was solely because of the fact that the only benchmarks I've found online that are still available are on roadways. or close to roadways. I've recorded lots of completely tree covered tracks that showed no problems, when over layed on top of tracks from the same trails from different days.

here's an example of the terrain i usually see, tree cover had not been an issue yet:

Screenshot_2016_09_18_04_58_44.pngphoto share

 

I'm just trying to find the faults. what you mentioned about converting quickly... my intent in the benchmark test was to give the phones the least amount of ON time before rebooting their coords at the benchmark, without refreshing their agps data, all while running airplane mode , to find it hope close to the benchmark they would be. i haven't tested benchmarks before, so this is all new to me, I'm just a single track junkie that enjoys finding new places to explore, the GPS tracking helps with that. those points were not averaged, just turned on, so started and picture taken. i hoped it would help people understand that i was giving the phones the worst conditions possible, for that benchmark location.

 

i kind of hoped the results would be picked apart testing flaws found and suggestions for future tests made, but nothing yet.

Edited by ohgood
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ahhhh, more testing....

 

yesterday we walked a fun trail that we've seen several times now. i passed some trail trash and remembered taking pictures of it a few months ago, along with a waypoint, and thought it would make a nice subject for accuracy in less-than-ideal conditions. after falling and watching my super expensive and brand new ($30, four years old, actually) casio skip across the rocks, I gathered myself and plopped the phone on the pile of trash and took a picture. apparently it's orientation has changed from normal to 'over on the side' or something, in the time since i took the picture and waypoint.

 

so anyway, here are the coords, and screenshots. have a chuckle knowing i came away from this with a little mud from the fall, and a bunch of hooo haaaa haahhahahaha's and some snorting towards the end of the laughter from the wife unit.

 

pic tours:

20160919_112227.jpg

 

20160919_112234.jpg

 

well, that was neato. even as the reported accuracy bounced around from 40ft to 10ft, it still got me within less than 10 feet from each cache / waypoint that i visited. i was really surprised to see that sitting all the way back against the wall of the 'cave' that i could still get any kind of a gps coordinate, with only 20% of the sky viewable. this weekend i'll probably revisit some more old waypoints to compare. i'm surprising myself. fun :)

Edited by ohgood
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these tests are proving very interesting. well, to me anyway, i notice it's getting pretty quiet. no biggie, carrying on! :-)

 

That might be because nobody knows what conclusions you are drawing. Are you claiming that phones under a clear sky converge quickly to the correct coords? I can't tell.

I agree, I'm not sure of neither what conclusions, or results, are attempted to be determined nor what the test objectives and requirements are.

 

Consequently, I might suggest expressing them in the context of the information provided here:

https://en.wikipedia.org/wiki/Design_of_experiments

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these tests are proving very interesting. well, to me anyway, i notice it's getting pretty quiet. no biggie, carrying on! :-)

 

That might be because nobody knows what conclusions you are drawing. Are you claiming that phones under a clear sky converge quickly to the correct coords? I can't tell.

I agree, I'm not sure of neither what conclusions, or results, are attempted to be determined nor what the test objectives and requirements are.

 

Consequently, I might suggest expressing them in the context of the information provided here:

https://en.wikipedia.org/wiki/Design_of_experiments

 

it's never going to be attacked scientifically, theorized, or presented in a precessional manner, by me. that would be a waste of time, and if it were actually that level of sophistication, free research for an organisation that doesn't need it or want it. an eighth grade student could pick it apart if they wanted, and find faults, and i would be perfectly OK with that. so long as they have fun and learn a little along the way.:-)

Edited by ohgood
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This is my bike rides for all of 2016 on Main Street here. 72 different tracks on different days using a Garmin 62s

 

LHscXww.png

 

It never strays into the median of Main Street (The dual lines on the right of the image)

 

All units today are pretty accurate, however some people including me over trust my units instead of realizing that the accuracy of GPSr/Cellphone of the person who placed the cache is even more important. But even if GPS units had 2 feet accuracy, I would still DNF some finds.

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This is my bike rides for all of 2016 on Main Street here. 72 different tracks on different days using a Garmin 62s

 

LHscXww.png

 

It never strays into the median of Main Street (The dual lines on the right of the image)

 

All units today are pretty accurate, however some people including me over trust my units instead of realizing that the accuracy of GPSr/Cellphone of the person who placed the cache is even more important. But even if GPS units had 2 feet accuracy, I would still DNF some finds.

 

thanks for giving this a look , and comparing your tracks. i agree, i would also miss a lot of caches, even with +-2feet .

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ohgood

 

Question (for the cell phone expert).

 

Since regulations require a cell phone to be able to dial 911 (even without a plan) and potentially give the phones location, how does that reconcile with "Airplane" mode and "Radios Off"?

 

in the past, pressing " call " after dialing 911 turned the radios on. i would assume roaming to whichever tower was available is what happens next?

 

location data hasnt been available to 911 operators we have talked with in the past, maybe it's fixed now? no idea.

 

if i ever get called "expert" , the crowd is either joking or ill informed ;-)

 

i bet since government agencies run the 911 services, were could find one station that can user location services provided by the phone, and another that doesn't know how.

Edited by ohgood
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in the past, pressing " call " after dialing 911 turned the radios on. i would assume roaming to whichever tower was available is what happens next?

Tx good to know

 

location data hasnt been available to 911 operators we have talked with in the past, maybe it's fixed now? no idea.

Phone data maybe not (not even now) tower triangulation probably as its passive I guess.

 

i bet since government agencies run the 911 services, were could find one station that can user location services provided by the phone, and another that doesn't know how.

I am sure the regulatory landscape (and technologies) are complex...

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after a few more (averaged) waypoint visits it seems like each device has a fairly consistent fingerprint of error. one device is off about five meter North, three West, almost each time. others are usually similar in maintaining whatever their "offset" is. of course there is still the real error of +/- whatever you have as an error, but the above seems fairly consistent.

 

i don't know how to (it if it's possible to) offset coordinate readings, but that might be worth looking into. map offsets are fine, but don't relate to waypoint vs good position, so not really help full.

 

i revisited some previously averaged waypoints.... very uneventful, just the same almost ten feet reference, sometimes sixteen.

 

I'd really like to find out how the location is obscured, and negate that at some point. ah well, another day.

 

:-)

 

anyone else out there testing or experimenting ?

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Use of the word obscured seems to imply intend. Is that what you meant to convey? I'm not trying to be picky here but there is a difference between the verb and the adjective.

 

To answer your question, I'd love to test the variance of my iPhone and GPS if I was aware of a known accurate point I could use for a reference.

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anyone else out there testing or experimenting ?

 

Nope. :D

 

Honestly, I think consumer-level GPS units are about as good as they're going to get for right now.

 

You're far more likely to have tree cover or canyons obstructing the signal, multi-path error, bad GPS antenna orientation, poor satellite constellation on a given day, or even wind up with a lemon of a GPS unit. Most of those variables are outside of your control.

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All GPS units are accurate enough to get you to the location to find the cache. However, not all caches are meant to be found easily no matter how accurate the coords are.

 

Even if they came out and made geocache units accurate within 2 inches, you would still not find all of them because the person who placed the cache might have their coordinates off by 30 or more feet. Might even cause more DNFs

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ohgood

 

Question (for the cell phone expert).

 

Since regulations require a cell phone to be able to dial 911 (even without a plan) and potentially give the phones location, how does that reconcile with "Airplane" mode and "Radios Off"?

 

Airplane mode turns off the transmitters. GPS is not a radio but a receiver. You can hunt for caches in Airplane mode as long as you have downloaded the maps for the area you are in.

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All GPS units are accurate enough to get you to the location to find the cache. However, not all caches are meant to be found easily no matter how accurate the coords are.

 

Even if they came out and made geocache units accurate within 2 inches, you would still not find all of them because the person who placed the cache might have their coordinates off by 30 or more feet. Might even cause more DNFs

It's assumed and accepted that GPSrs and phones are accurate enough for geocaching (in this thread), the OP was interested in accuracy and response times hence the discussion.

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ohgood

 

Question (for the cell phone expert).

 

Since regulations require a cell phone to be able to dial 911 (even without a plan) and potentially give the phones location, how does that reconcile with "Airplane" mode and "Radios Off"?

 

Airplane mode turns off the transmitters. GPS is not a radio but a receiver. You can hunt for caches in Airplane mode as long as you have downloaded the maps for the area you are in.

Thanks Walt, my question was specifically how does the requirement for phones to dial 911 work in airplane mode. ohgood answered in post #27.

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ohgood

 

Question (for the cell phone expert).

 

Since regulations require a cell phone to be able to dial 911 (even without a plan) and potentially give the phones location, how does that reconcile with "Airplane" mode and "Radios Off"?

 

Airplane mode turns off the transmitters. GPS is not a radio but a receiver. You can hunt for caches in Airplane mode as long as you have downloaded the maps for the area you are in.

Thanks Walt, my question was specifically how does the requirement for phones to dial 911 work in airplane mode. ohgood answered in post #27.

I'm not sure if the following would work in Airplane mode as I'm not that savvy with the terms used.

 

"112 is an international standard emergency number which can only be dialled on a digital mobile phone. It is accepted as a secondary international emergency number in some parts of the world, including Australia, and can be dialled in areas of GSM network coverage with the call automatically translated to that country’s emergency number. It does not require a simcard or pin number to make the call, however phone coverage must be available (any carrier) for the call to proceed."

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I believe *112 works only on GSM phones (primarily AT&T and T-Mobile) here in the U.S. Here, those carriers automatically translate the number to "911".

 

is it *112, or just 112 ? I'm not familiar with that at all, and don't want to mess with accidental emergency calls. thanks

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My bad. Here in the U.S. when it's provided, it's just 112. Actually, I think it's that way in Europe as well. No "*". Perhaps one of our Euro members can chime in on that.

 

I've never seen a phone number start with "*", 112 is all that's needed.

Reloading on a prepaid can be done with *1234*123456789012345# if a code is bought.

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last weekend we used locus in a casio c811 to record the track from a morning of frisbee golf. personally i'd give it a 1/5 for terrain since riding a bike wouldn't be difficult, and 3/5 for tree cover but given what i've seen from geocaching it would probably be considered a '3/5 hiking trail' with '4/5 tree cover'. the phone was either in a pants pocket, or the bottom of a backpack, unless i was recording a waypoint.

 

according to the automagical track coloring, the worst reported accuracy was 43feet (red) and the best 10feet (blue) and the average around 30ft (green). waypoints were not averaged, or given any longer than it takes to type "launch 3" for each waypoints name. again, the gps wasn't given any help by standing still for ten minutes, averaging, or holding it up on a 20 ft pole to help it see more satellites.

 

i did notice that what would normally be a 10ft reported accuracy when attached to my handlebars was instead a 30-40ft accuracy while in a pants pocket, or the bottom of my backpack. i'm not planning on carrying a surveyors pole on any of my next hikes/bikes, so this is unlikely to change in the future.

 

anyway, a picture is here

Screenshot_2016_10_16_04_58_01.png

 

i hoped to find another gpx on gpsies/everytrail but failed to find one to compare. if anyone would like to provide their gpx track from the location, that would be pretty cool to have on hand.

Edited by ohgood
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