Real-life comparison of GPS receivers.

[Guest laurie]

Well I am fairly new to this (have known about Geocaching since the start - but never actually did one). I am also very familiar with the nautical uses of GPS. OK - with that said...

 

After much research - searching the Net - reading posts etc. I have decided that what would be really interesting (an excuse for a group cache??) would be to gather as many different GPS units together in one place and run a series of tests to determine which is better under what circumstances.

 

All I have been able to find are Manufacturer specification comparison and some people's "gut feel" between different units. I would like to conduct a slightly more controlled test. Some things I was thinking were - actual timing of "cold" aquision (after unit is off for 6+ hours) timing of warm aquision. Functionality in the open, under light trees, heavy foliage, etc. If there is a surveyer that could verify the actual Lat/lon coords that would be great - or use a topo map and traditional methods to determine lat/lon of the test area.

 

I am up here in the North East so we have some interesting GPS type problems - *heavy* tree cover, humid (snow/rain) and lots of granite. And was wondering if a group of people would be interested in doing something like this.

 

What do you guys think???

[Guest laurie]

Humm after looking through the forum breakdown by geography - maybe I should have said "New England"

 

(Never in a million years would have guessed that Virginia/DC/Maryland would be considered "North East" I have always considered them "East")

[Guest Mopar]

Have you seen http://joe.mehaffey.com ?? They have tons of independent reviews and comparisons. I found it very helpful in comparing different units.

[Guest arffer]

quote:

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Originally posted by Mopar:

Have you seen http://joe.mehaffey.com ?? They have tons of independent reviews and comparisons. I found it very helpful in comparing different units.

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This site is where I first noticed reviews showing how sensitive the Lowrance GM100 was compared to other GPSRs.

 

http://joe.mehaffey.com/gm100rev.htm

http://celia.mehaffey.com/iraw/gm100.htm

[Guest laurie]

Ok, I guess the whole concept of a group of people in the same area of the country comparing GPS receivers is a lost idea.

 

I *have* checked out those websites been checking them for the last year+ but the reviews are very subjective - I thought it would be interesting to do a better test (and a great excuse to meet other like minded folks).

 

Guess I will have to play on my own. :/ in a week I will have 3 different GPS receivers to compare so that will have to do.

[Guest Kerry]

In general it can be difficult to compare units which can't be configured and many rec units don't have that capability. Specifications have always been a bit biased.

 

Historically accuarcy used to be one and that was always overstated in manuals. CEP was probably "invented" for that specific reason (to make it sound better than it actually was). Another is the 12 channel myth (but that was a misunderstanding anyway right from the start). Then there's Position updates along with a few others.

 

In comparing different types of receivers at a grass roots level one needs to separate the "actual GPS" side of things from what most see as "the GPS", which is more the outside user interface side of things.

 

Cheers, Kerry.

[Guest makaio]

short of having a surveyor actually mark a location for you to use to test handheld unit accuracy, you can use known National Geodetic Survey benchmarks in your area. These are used by surveyors as starting points to measure off of when marking locations for railroads, highways, etc.

 

Follow the data sheets link and do a radius search from your location to locate some nearby.

 

[This message has been edited by makaio (edited 18 October 2001).]

[Guest laurie]

as integral part of the GPS can not be something to be "done without".

[Guest Cape Cod Cache]

For what it's worth... A few years back I used to sell handheld GPS and did my own "shoot-off's" among the units I had available. I did all these in an open parking lot. Mind you this was during SA, but the shift would be the same for all the units. I used like priced units between brands. Garmin always got the fastest initialization for brand new, out of the box as well as cold start aquisition for previously used units.

 

The 'accuracy' between units was negligable, even between like units. A bit of fluxuation, but nothing that should impair the uses for a hand held, or at least what a hand held owner should expect. (That's a loaded statement !) I have a GPS 48, I could have got any unit my little heart desired, but I wanted it for use on the water and I liked the feel of it in my hand. I have since used it plugged into a mounted GPS's antenna with differential, and got the same numbers that the boat's GPS had. Without DGPS the difference was negligable. I had similar results compared to a high-end professional grade marine unit.

 

Granted, these aren't lab-coat experiments, just observations I've made by having a few different models at my disposal. If you're ever in the Mid-Cape area, I'd be happy to compare GPS's.

 

[Guest Cape Cod Cache]

For what it's worth... A few years back I used to sell handheld GPS and did my own "shoot-off's" among the units I had available. I did all these in an open parking lot. Mind you this was during SA, but the shift would be the same for all the units. I used like priced units between brands. Garmin always got the fastest initialization for brand new, out of the box as well as cold start aquisition for previously used units.

 

The 'accuracy' between units was negligable, even between like units. A bit of fluxuation, but nothing that should impair the uses for a hand held, or at least what a hand held owner should expect. (That's a loaded statement !) I have a GPS 48, I could have got any unit my little heart desired, but I wanted it for use on the water and I liked the feel of it in my hand. I have since used it plugged into a mounted GPS's antenna with differential, and got the same numbers that the boat's GPS had. Without DGPS the difference was negligable. I had similar results compared to a high-end professional grade marine unit.

 

Granted, these aren't lab-coat experiments, just observations I've made by having a few different models at my disposal. If you're ever in the Mid-Cape area, I'd be happy to compare GPS's.

 

[Guest geospotter]

With all of the theory and sales fluff nothing beats "real world" tests.

 

I like the idea. I'm in Massachusetts. Where in NE are you?

 

Bud

[Guest Kerry]

The following is a "real" world accuracy comparison between old & new technology both before and after Selective Availability. One will notice that there's no mention of makes/models as that not the purpose of this particular report.

 

http://www.cqnet.com.au/~user/aitken/gps/gps_5v12.htm

 

Just note that "Predictable accuracy" is no longer defined in the new accuracy specifications. In the context used in the above it is the same as the new "Positioning Accuracy" definition.

 

Cheers, Kerry.

 

 

[This message has been edited by Kerry (edited 19 October 2001).]

[Guest found]

http://gearreview.com/gpsreview98.asp#MTracker

 

I just posted this in another topic.. but i see it may belong here...

[Guest found]

http://gearreview.com/gpsreview98.asp#MTracker

 

I just posted this in another topic.. but i see it may belong here...