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SA ?


ragtop1968

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There seems to be two SAs that I keep hearing about. One is interference from the military when they

want to throw civilian GPSs off track.

 

But I thought I read somewhere about static acceleration where a GPS will not return a new position if you haven't moved so many meters or your going under 3mph. This seems to be my problem. My Rikaline X7 bluetooth GPS works fine in the car but is all but useless on foot as it is so slow to update position. You can walk all over the place in a 60 foot area and it shows you in the same spot.

 

I haven't been able to find out how to turn this feature off. Is there a way to know before you buy a GPS

if it has this annoying feature or not.

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I haven't been able to find out how to turn this feature off. Is there a way to know before you buy a GPS

if it has this annoying feature or not.

 

It has been turned off by the Clinton Administration almost 7 years ago.

 

Wikipedia:

 

The military resisted for most of the 1990s, but SA was eventually "discontinued"; the amount of error added was "set to zero"[11] in 2000 following an announcement by U.S. President Bill Clinton, allowing users access to an undegraded L1 signal. Per the directive, the induced error of SA was changed to add no error to the public signals (C/A code). Selective Availability is still a system capability of GPS, and error could be in theory reintroduced at any time. In practice, in view of the hazards and costs this would induce for US and foreign shipping, it is unlikely to be reintroduced, and various government agencies, including the FAA,[12] have stated that it is not intended to be reintroduced.

 

GermanSailor

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No, I am having trouble with the other SA. Where the GPS doesn't update position unless you are traveling at a certain speed meant for driving so that bad reads don't have you bouncing all over the road when stopped.

 

But it really is crap when trying to find a geocache on foot. I had found a program for turning it off, but it does not work with the rikaline X7.

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If that's the model I saw when googling, how are you viewing your location? The model I saw didn't have a screen, so are you using a laptop or pda app? While it does seem strange that the unit can't be adjusted to update its position at low speeds, I'm guessing they've aimed it squarely at the automotive market.

 

Sorry I couldn't offer any advice.

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Update rate is a function of the GPS, and possibly the software. You can read the manual and see if it is adjustable somewhere, but I suspect not. It's likely sold as an automotive GPS, and thus a low update rate, and thus cheaper to produce.

 

I did finally find a few reviews, and this seems to be a rather old model, as GPS receivers go, SIRF II chipset, but the update rate should be OK. What software are you using, on what OS? That is probably what is driving the update rate.

Edited by NightPilot
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I don't have anything bluetooth, but my understanding it that it transmitts data short distances. So what is this bluetooth transmitting to? Is the antenna on the car, and you are wondering around with the unit? Is it saying "your position is still over here where the antenna is?

 

Another thought if that isn't true. Some units have an adjustable speed filter. You may have a 1 second update, but your speed filter may be set so the position takes big jumps.

 

One more thought. "Lock on roads" can hold your position at the road you just walked away from. It happens to me every now and then. You can disable "lock on roads" on may units.

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Assuming you didn't throw this thing up on the dashboard and then wander off with your Ipaq, yes you are right. The sirf chip, I now recall reading, has a feature that keeps your position stable unless you are trucking along. Basically a non-navigation feature. Not a popular thing with Garmin and so that featurless feature has been disabled on most units. Instead of seeing the position wander when standing in one place this rediculous feature made you think it was a super stable unit. (Well the darn thing was stable because it wasn't navigating.) At least that is my understanding. Anyway, I hear it's been fixed, (except for maybe you model.)

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Assuming you didn't throw this thing up on the dashboard and then wander off with your Ipaq, yes you are right. The sirf chip, I now recall reading, has a feature that keeps your position stable unless you are trucking along. Basically a non-navigation feature. Not a popular thing with Garmin and so that featurless feature has been disabled on most units. Instead of seeing the position wander when standing in one place this rediculous feature made you think it was a super stable unit. (Well the darn thing was stable because it wasn't navigating.) At least that is my understanding. Anyway, I hear it's been fixed, (except for maybe you model.)

 

I use it with a laptop in the car and a IPAQ 4355 on foot using Microsoft Streets (which is also crap cause they fail to mention that all the great features of the PC version doesn't transfer to the PDA version) and GPStuner which I would like to use when close to a cache for it's digital compass, but with the Rikaline not updating position it makes GPStuner nearly impossible to use.

 

Soooo....if I got a new sirfIII GPS would there be little chance that it would have this annoying feature. I wish there was something in the specs that I could be sure that it does not have this feature.

 

I notice in some specs when giving velocity it says (without SA). I don't know if they are talking about this or the military thing.

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There seems to be two SAs that I keep hearing about. One is interference from the military when they

want to throw civilian GPSs off track.

 

But I thought I read somewhere about static acceleration where a GPS will not return a new position if you haven't moved so many meters or your going under 3mph. This seems to be my problem. My Rikaline X7 bluetooth GPS works fine in the car but is all but useless on foot as it is so slow to update position. You can walk all over the place in a 60 foot area and it shows you in the same spot.

 

I haven't been able to find out how to turn this feature off. Is there a way to know before you buy a GPS

if it has this annoying feature or not.

From the manufacturer page talking about current models http://www.rikaline.com/bluetooth_gps.htm :
Stay still when you place it. No sliding whatever you make sharp turn or sudden stop while remaining easy pick up if needed for use off the car.
Sounds like they are very proud of this "feature" Edited by John E Cache
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There seems to be two SAs that I keep hearing about. One is interference from the military when they

want to throw civilian GPSs off track.

 

But I thought I read somewhere about static acceleration where a GPS will not return a new position if you haven't moved so many meters or your going under 3mph. This seems to be my problem. My Rikaline X7 bluetooth GPS works fine in the car but is all but useless on foot as it is so slow to update position. You can walk all over the place in a 60 foot area and it shows you in the same spot.

 

I haven't been able to find out how to turn this feature off. Is there a way to know before you buy a GPS

if it has this annoying feature or not.

From the manufacturer page talking about current models http://www.rikaline.com/bluetooth_gps.htm :
Stay still when you place it. No sliding whatever you make sharp turn or sudden stop while remaining easy pick up if needed for use off the car.
Sounds like they are very proud of this "feature"

 

Funny....but I think they are talking about the physical properties of the case there.

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'Without SA' means the military thing, and it's off, and will stay off. The other use you made of SA is something I've never heard of.

 

I don't use a PPC, nor GPSTuner, so all I can do is suggest reading the manual for both, and see if there is a setting to change the update rate or anything else.

 

Now I don't where I got the term static accerelation......I looked up that software that will turn the feature off some GPS receivers called sirfdemo http://www.gpspassion.com/forumsen/topic.asp?TOPIC_ID=25575

 

And they use the term static navigation explained as follows:

 

Current road navigation software is designed for GPS receivers that only operate with good signals so accuracy will be in the 15 meter area. Such software will "snap" the position to the closest road so in a dense urban area, with degraded accuracy it's going to be easy to make the wrong decision and produce "uncosmetic" results and possibly force a trip recalculation.

 

Instead of redesigning navigation software to take this account (one could imagine some type of dynamic filtering based on DOP) and risk increasing the processing load on the PDA and hurt user experience, the easy fix is to implement this fix directly by having GPS manufacturers activate "Static Navigation" by default and therefore freeze the position using some complex algorithms mainly speed dependent. The problem with this is that this will considerably hurt low speed pedestrian use, with the speed staying on "0" and 50 meter jumps (update threshhold). If you want to use your GPS receiver outside your car, you'll need to disable SN

Edited by ragtop1968
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