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(Which) External antenna for Garmin GPSmap 64s?
g_org
0 Points
Hi,
I'm new to the mapping scene and next week I am headed to France for some field work. A friend of mine is giving me his Garmin device (GPSmap 64s) and I am wondering how I can improve the accuracy of my measurements.
The setting will be a light forest, with a lot of open space and a few boulders ranging from 1-5m height. Here are my questions:
- Would you recommend buying an external antenna for the mapping?
- Will the increase in accuracy be likely worth the investment (if seen antennas as expensive as the GPS device itself)?
- If so, which one would you suggest (I am looking for a good price/value not high-end performance)?
Thank you for your help! I am really excited about this and hope to hear from you.
George
I'm new to the mapping scene and next week I am headed to France for some field work. A friend of mine is giving me his Garmin device (GPSmap 64s) and I am wondering how I can improve the accuracy of my measurements.
The setting will be a light forest, with a lot of open space and a few boulders ranging from 1-5m height. Here are my questions:
- Would you recommend buying an external antenna for the mapping?
- Will the increase in accuracy be likely worth the investment (if seen antennas as expensive as the GPS device itself)?
- If so, which one would you suggest (I am looking for a good price/value not high-end performance)?
Thank you for your help! I am really excited about this and hope to hear from you.
George
Comments
I need it to be within 5m (less would be better... but really, consistency is more of a concern), but again, this is a test run, so it is perfectly fine for me to tinker with this.
Tim's point about expectations is right on target. Consumer devices like the 64 are not likely to give you any better than +/- 5 meters regardless of what you do. The very expensive antennas you have seen are probably intended for use with specialized survey grade gps units that cost thousands of dollars. In the consumer space, spending more money is not likely to give you more accuracy. A ~$100 device like the eTrex 10 is going to be just as accurate as the ~$700 Monterra. Spending more money just gets you more "bells and whistles".
To get the best accuracy with your 64, use the "waypoint averaging" feature. If you stand stationary, the device takes a position fix every second and averages the results. This usually gives better accuracy, but there are a lot of variables such as the position of the satellites at the time you take the measurements.
Would someone recommend an external antenna, just for the purpose of having the receiving 2m higher, than you usually hold your device (so it is less likely to be covered by myself or surrounding objects)?
GPS is essentially a radio broadcast your GPS receiver listens to, very similar to FM or AM radio. FM radio operates at 88 - 108 MHz while GPS operates up near 1100 - 1600 Mhz. Recall old radios with telescoping antennas and how much of a difference extending the antenna can make.
An external antenna will help in a similar fashion. It isn't that the external antenna in a different location than the GPS (with exception for the scenario noted above where the GPS is blocked inside something like a car) but that the antenna is longer and larger and thus is able to cast a bigger net to catch more signals.
The big, blocky antennas on older GPS devices helped cast a bigger net when the receiver chip wasn't as good at picking out weaker signals. As the chips became more sensitive the bulky antennas were no longer necessary and wen't out of style. But they are still useful in casting a bigger net.
Don't get me wrong, I don't think it will make a huge difference, but an external antenna does provide more of an advantage of simply putting the receiver in a different location.