Calibrating or Resetting my GPS III+

[Guest a_calder]

I have been wondering about the accuracy of my GPS III+ for a while now. I have noticed that my coordinates always seem to be a ways out, based on published locations.

 

I have also had a few comments about coordinates that I have posted being a little bit off.

 

Is there a way that I can check the accuracy of my unit? Is there some kind of diagnostic mode or reset?

 

Part of the problem is that when I got it, I was fooling around with the System settings, and though I think everything is normal, my conspiracy theory mind has convinced me that I have screwed it up completely.

 

What can I do to assure myself that my readings are the best that I can get on my unit?

 

Thanks,

Alistair

[Guest mcb]

If you want to completely reset your unit back to factory defaults then you will need to hold the enter/mark key down while turning the unit on. This will erase all waypoints tracks and routes and most any other user data you have in it. Maps may or may not survive this. I don't remember. None the less back up your stuff and reset the unit. Now you will have to give your GPS about 20 minutes to and hour to get locked on again since you will have also erased all the data for the satellites.

 

You might just make sure that you are using the WGS-84 datum you should be OK. The other likely Datam would be NAD-27 if you are using old USGS topo maps. There are really only two setting. One is the datum and the other is the grid.

 

There is nothing else really to "calibrate" on a GPS.

 

Later

mcb

[Guest Gliderguy]

If I remember right there is a user datum where you can specify whatever offset you like. If you happened to be using this datum your points would be off by the specified amount. I believe a hard reset would default you back to WGS 84. There was also a way to calibrate the internal temperature sensor. The temperature of the unit aparently has some effect on the internal electronics speed and thus the distance calculations. I am not sure if a hard reset sets this back to some nominal value

 

One other thing that happens when a GPSR is used infrequently, is that the almanac data gets old. If the GPSR is only turned on for a few minutes to get a position, then turned off, it never gets an updated almanac. I discovered this with a unit (Garmin III) that had been off for months. It disagreed with my newer, more often used Garmin III+ by over half a mile. After leaving the III on with a good lock for about half an hour, it agreed with my newer unit within several feet.

[Guest gstrong1]

a_calder.Hit,menu,menu, rocker down to setup,enter,rocker over to "position", make sure it's set to --position format=hddd mm.mmm' & --map datum=wgs 84. If not, just rocker down to highlight either one, hit enter & your options will pop up. Highlight the right one, hit enter.

 

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Gary "Gimpy" Strong

Rochester,NY

 

[This message has been edited by gstrong1 (edited 19 November 2001).]