You are viewing this forums as a guest which limits you to read only status.
Only registered members may post stories, questions, classifieds, reply to other posts, contact other members using built in messaging and use many other features found on these forums.
Why not register and join us today? It's free! (We don't share your email addresses with anyone.) We keep email addresses of our users to protect them and others from bad people posting things they shouldn't.
I am marking an underwater site out with Waypoints. I wonder how accurate the GPS is on the CTX... 1 meter? 5 meters? 10 meters?
Doesn't the US military/ US government have some kind of throttle on how accurate GPS can be for public purposes? Or does the CTX use European positioning satellites for the GPS?
I tested it one time. I posted a find point and then went on th detect about 25 feet away. I then tried to walk back to original find and could not locate it. The machine seemed to take a lot of time to refresh.
The US government no longer restricts GPS accuracy (go to GPS.GOV/GPS accuracy). The WAAS (Wide Area Augmentation System) covers North America. you can get a lot of info just by doing a web search on that. What restricts accuracy is basically the expense. GPS surveying equipment is extremely accurate. The more satellites connected, the better the accuracy, but with very high equipment costs. I've only used the GPS on land, and feel metal detecting, I have found the GPS accuracy and operation, to be very good with my CTX. Last summer I recorded WP and many FPs so once the crops are out this fall I can return to the locations. Based on a series of nails that I set over a year ago, I will normally be taken within 10 feet or less from my nails. Also, for a check, I have also acquired documented GPS coords for a USGS benchmark, put them into the CTX to check how close I would get. I was in 5-8 ft of the BM. It won't get you right on the ol' knat's ---, but very close.........
Accuracy of GPS is a game of percentages. First of all, there are some system limitations.
Our CTX's (and every consumer grade) GPS receiver receives a signal that (in theory) allows to compute the position within certain error.
75% of the time error will be smaller than 5 ft,
95% of the time error will be smaller than 10 ft
99% of the time error will be smaller than 30 ft
The above values are good for most of the world and can be achieved with clear view of the surrounding sky. Having tall buildings (urban canyons), dense foliage or a mountain side obstructing portion of the view may adversely affect accuracy and there is little one can do about that.
For the reasons above, consumer grade GPS receivers can not be used to conduct (for example) legal surveys so, don't blame your CTX for all of the inaccuracies.
The ugly truth is that; if you record a point with a 5 ft error, when you try to come back to it, you can easily have an error that is 5 ft the other way and end up 10 ft from the intended target.
One way to deal with it is to initially record several way-points, in (say) 30 second intervals, at the same position and than average the position. The more points, the merrier! Than, in Xchange2, you can display all these points (they will be very close to each other. Delete any that are outside of the main group than create a new waypoint in the center of the group. Yes, it takes time and some work but, if you need results, it may be worth it. Using a sample of 30 points taken over a period of 30 minutes, your averaged waypoint should be within couple of feet from the target thus allowing you to easily return to within 6 feet or better.
Another VERY IMPORTANT factor affecting accuracy of CTX's receiver is; it needs to know precisely the orbital data of the GPS satellites. It receives the data after it is turned on and (unfortunately) forgets it all if it's turned off. To make a long story short; to count on any accuracy, after the GPS / CTX is turned on and acquires position log, you will need to wait almost 20 minutes for it to gather this info from the satellites. Before that happens, the position displayed could be even hundreds of feet off. Once these data are downloaded, you will get the maximum possible accuracy.
For that reason, I turn the CTX and GPS on as soon as I unpack it on the site and do not turn it off when taking a break during hunt.
