"Start ext GPS" option necessary?

I use an external BT GPS and the Bluetooth GPS provider app, BlueGPS (bluetoothgps4droid 1.2.2), to allow the external gps to be used instead on the phones gps. My question is when I want to start recording a track, should I use the "Start ext GPS" option or just the normal start gps option?

My understanding is that the BlueGPS app traps requests to the internal GPS and forces the use of the external gps unit so is that start ext gps option required? I ask because sometimes using the start ext gps option causes oruxmaps to freeze sometimes.

As I understand it, there are two options to use an external GPS receiver with Oruxmaps.

One is to use an additional application which provides the data of the external receiver by use of the "test GPS coordinates" feature (don't know the exact name) to all applications. However, some applications are pretty stubborn and require internal GPS to be switched on to use GPS coordinates provided that way at all.
If you can make it work with your phone (Galaxy S is a bit tricky but can make to work), this will provide GPS coordinates nearly as if they were from the internal GPS. This works also with Oruxmaps in the way that you use it, by the "Start GPS" command.
For this I use the "Bluetooth GPS" application.

Oruxmaps also has the feature to directly receive GPS coordinates from an external device via bluetooth. This will only receive the coordinates within Oruxmaps. For me, this has been working flawlessly as far as I can remember. For this feature, you use the "Start external GPS" command. Before you can use it, you have use the Oruxmaps settings to configure the external GPS device which must have been paired with the phone before.

Both features should be mutually exclusive at the same point in time, I think.
Usually I use the "general" way to provide external GPS coordinates just to provision other apps with coordinates as well. If you only want to provide coordinates to Oruxmaps, you can safely use the built-in option.

Thanks for your comprehensive reply c65.

I've been using and external app "Blue GPS" to provide the gps coordinates but have also at the same time always used the "Start Ext GPS" option. So I should really be using just the Start GPS option (I also need to have the internal GPS switched on but I think it's not actually using it as the battery drain is not high). I'll need to experiment a little with just using the built in Ext GPS functionality from Oruxmaps without the Blue GPS app and see if that works on my Galaxy S2. I'll also try using just the "Start GPS" option when using the Blue GPS app to see if that works.

For the last months I've been getting incorrect altitude values (usually showing -47m when I'm at least 10m above sea level). Maybe trying a different way will fix that too.

cyberdude wrote:Thanks for your comprehensive reply c65.

I've been using and external app "Blue GPS" to provide the gps coordinates but have also at the same time always used the "Start Ext GPS" option. So I should really be using just the Start GPS option (I also need to have the internal GPS switched on but I think it's not actually using it as the battery drain is not high). I'll need to experiment a little with just using the built in Ext GPS functionality from Oruxmaps without the Blue GPS app and see if that works on my Galaxy S2. I'll also try using just the "Start GPS" option when using the Blue GPS app to see if that works.

For the last months I've been getting incorrect altitude values (usually showing -47m when I'm at least 10m above sea level). Maybe trying a different way will fix that too.

Hi;

About altitude problem:

check/uncheck, in settings--GPS-->'NMEA altitude correction' if you want to get the altitude over the geoid instead the ellipsoid,

orux

orux wrote:
Hi;

About altitude problem:

check/uncheck, in settings--GPS-->'NMEA altitude correction' if you want to get the altitude over the geoid instead the ellipsoid,

orux

I seemed to have fixed the problem. I need to have the NMEA altitude correction off. I tried this before but I was using the Blue GPS app and using the "start ext GPS" option at the same time which seems to affect and produce an incorrect altitude reading.

Now I just use the "start ext GPS" option directly with my BT GPS device without the Blue GPS app and it all works fine.