07-04-2005, 07:10 PM #1
GPS/Radar Compared Side by Side *****A Must Read**********
For starers the Radar used was a Stalker that was just calibrated 1 week ago. It is used by my friends transmission shops and they have to show that it is 100% correct for it to hold up in court if needed.
There were 3 GPS's tested 2-Garmin and 1 other I do not know what kind but it looked sort of cheap compared to the others.
1 Garmin showed exactly 1 MPH to fast Approx. $250
1 Garmin showed exactly 1 MPH to slow Approx $600 color screen unit
The other brand would not show consistant runs, it would be slow one run and fast the next. He claimed that it was not picking up a good signal out there. I do not know much about GPS's so I do not know if this is true or not??? The other guys worked fine.
We ran 6-8 runs on each unit and they were always the same.
The moral of this I guess is that if you can find someone to test your GPS with against radar some of you may find you are really going faster than you think and others may be a little disipointed.
07-04-2005, 07:26 PM #2
I've done that test before with a Stalker and Garmin Etrex ($99) GPS. My GPS always read like .5-1.0 MPH slower. I just attributed it to that one radar (which was also tuned that day)
I figure its all relative. Velocity is an arbitrary concept we concocted, so it's definitely subject to argument I don't care if I am *exactly* right on my speeds as long as I use the same instrument every time to capture the differences. Since I can easily use the Etrex daily, its my instrument of choice.
Here's another phenomenon I've noticed. The Garmin Etrex and Legend that I have will always be dead on with each. A .1 MPH variance if any. But I also have a Garmin Foretrex, and it won't read the same speeds a lot times that the other two do. I am assuming that this has something to do with its ability to capture speeds X times per whatever time variable.
07-04-2005, 07:38 PM #3
Do GPS's have to acquire satellites?
Can being connected to more of them help to be more accurate?
The guy with the odd GPS said he was only getting like 4 and he normally sees 6-8. I thought that he was embarrassed his did not compare to the others out there.
07-04-2005, 08:48 PM #4
A GPS needs at least 3 satellites. The more it can aquire the better the accuracy.
07-04-2005, 08:54 PM #5
- Join Date
- Apr 2005
I have a Garmin 72 GPS and a Decatur K Band Radar without tenths of mph. Tuning forks to check radar calibration. They both read the same mph. Thats with 3 satelite connections.
07-04-2005, 10:37 PM #6
I have two GPS. One is a Garmin Etrez and the other is the Garmin Geko. I get the same numbers all the time on both units. Once in a while one will be 0.2 mph different from the other one.
07-05-2005, 09:35 AM #7
Radar is not always an accurate way to read speed on the water. A boats rooster tail or spray can make a difference in the speed readings. Any angle, however slight from dead on , either comming at, or going away from the radar gun, will affect the readings. The angle will make the speed reading "conservative". The only way to get a true reading on water is to have the gun mounted in the boat and aimed at a stationary object. such as a bridge. Aiming the gun down at the water while riding will not register speed. Aiming it down at a roads surface will. When I was with the SCPD Marine Division. we played around with the guns and found the above to be true.
GPS is usually dead on, but satellite signal strength has a lot to do with the readings. I once had mine read 10mph while walking from the parking lot to the ramp !!
07-05-2005, 01:09 PM #8
What is a good GPS that will do a peak speed hold and also be able to be used around town and in the car as I get lost a lot.
I like the Garmin that is built into a PDA.
I would like to try one of these as it is really hard to have someone hold the radar gun.
I could do my comparrisons and see how mine did against the gun.
07-05-2005, 03:41 PM #9
Also keep in mind that the two gps units in question probably have different antenna designs. (the etrex uses a different design then the 76 series for instance)
some gps's are designed to get best reception when mounted horizontal, and some are designed to be mounted vertical.
The only way I could see to set a baseline between the two gps's is make sure they both are at the same accuracy reading, and go to the sat. screen and see which ones are locked in and what the signal strengths are for each one.
Users Browsing this Thread
There are currently 1 users browsing this thread. (0 members and 1 guests)
By flyboy in forum Yamaha PWC Performance (2-stroke)Replies: 18Last Post: 07-10-2007, 10:28 AM
By OzarkGPR in forum Polaris Open DiscussionReplies: 11Last Post: 04-12-2007, 09:08 PM
By Antiguan FZR in forum 4-Tec PerformanceReplies: 5Last Post: 03-16-2007, 09:23 PM
By Shibby1485 in forum 4-Tec PerformanceReplies: 14Last Post: 05-18-2006, 12:45 PM
By Mark S in forum 4-Tec PerformanceReplies: 2Last Post: 05-17-2006, 09:08 PM