Device settings - preferred parameters

gpsn00b's picture

Salut all!

Please check my settings and comment if I should select/deselect/change some of the options.

Also, I've just turned "use SBAS" off and while I haven't tried the device outside after this, if I deselect "DGPS" in track/waypoint filters on my current track, I get _no_ data at all. If I select it back, then under the "valid" column in track/waypoints I only see "DGPS" and no other type. Why is it so? Should I not deselect SBAS then?

Thanks in advance!

mdeweerd's picture

The settings you show in your

The settings you show in your image do not impact the values already recorded in memory - unless you proceed to an erase which would simply remove them from memory.

So when you deactivate SBAS, this will apply to future position fixes and therefore also to future recorded positions.

On the filter panel the typical user would have to leave DGPS active because this corresponds to valid positions.  A slightly more advanced user might want to deselect SPS if he only wants DGPS positions.

If you want to save on memory, you can deselect the 'GPS Fix Type' and 'DSTA' .  When SBAS is inactive, you will only get 'No Fix', 'SPS' or 'Estimated' positions and you probably are only interested in 'SPS'.  'No Fix' and 'Estimated' positions can be determined from the HDOP and PDOP values that will be 99.9 - so it is easy to filter those out.  Further if you check 'Valid fix only', 'No fix' positions should no longer be recorded (unless you have an old device).

Because you have a 300ms fix, you surely want to activate the 'MILLISECONDS' to distinguich between 3 positions recorded in the same second.

Only one of PDOP or HDOP should be sufficient to, but that is at your discretion of course and NSAT is a nice extra to further filter out bad positions.

gpsn00b's picture

Thanks.  On the filter panel


On the filter panel the typical user would have to leave DGPS active because this corresponds to valid positions

But if SBAS is turned off, then how will I get DGPS? As you can see I am not really understanding this part. 

Also, should I get rid of 300ms fix and/or change it something else? What impact does it have? 

P.S. I always "erase" memory after a day of use and set the format ;)

mdeweerd's picture

You said: "I haven't tried

  • You said: "I haven't tried the device outside after this".  So you still have DGPS in your logger because there are no new positions logged and the old ones have DGPS.  The new ones will not have DGPS.
  • If you put the fix at 300ms, the position will be determined every 300ms, and, the log conditions are checked at that time.  So if you move at least 5km/h, you'll get about three positions logged per second.

If you have erased the device after changing SBAS, then there is something going on that I can not yet imagine based on your statementss. 

gpsn00b's picture

What I meant was that I

What I meant was that I unchecked SBAS, set format/erased memory but haven't yet tested the device outside. However, from my previous experience I know that if I uncheck "DGPS" in the filter tab, I get no track/waypoints at all. So essentially I am wondering why is that AND if by unchecking SBAS I will not get be able to build the track after I try the device outside.

mdeweerd's picture

Ok, then that is because

Ok, then that is because previously all the logged positions were using SBAS information and labeled as 'DGPS'.  If SBAS information would not have been available to the device, it would have been unable to use SBAS information and hence have labeled the positions as 'SPS'.

The new positions should no longer use SBAS because you unset that and these positions should hence not be labeled as 'DGPS' but as 'SPS'.

SPS and DGPS rely on the same positioning mechanism, but DGPS adjusts the position with information received from 'SBAS' (WAAS/EGNOS/...)

gpsn00b's picture

A-ha! Now it makes sense

A-ha! Now it makes sense :) 

I'll test to see if DGPS was detrimental to the accuracy or if there is no difference at all. Also based on your advice I turned AGPS off. 

Thanks for the great program. 

gpsn00b's picture

One more thing, BT747_64b.exe

One more thing, BT747_64b.exe - is that for 64-bit systems? I am running Windows 7 x64 and while the programs runs, I can't connect to the GPS device. It connects fine with BT747.exe.


mdeweerd's picture

BT747_64b.exe is for 64 bit

BT747_64b.exe is for 64 bit java.

You can run 32 bit java on a 64 bit system which you are probably doing.  In that case you need to use BT747.exe to use the 32 bit serial driver.

gpsn00b's picture

Yes, since I am using IE

Yes, since I am using IE 32-bit sometimes, I have 32-bit Java installed. OK.