No output from `/fix` in `utbm_robocar_dataset_20190418_roundabout_noimage.bag`

[xingyuuchen]

Hi,

First, thanks for sharing your dataset!

I am tring to get gt trajectory from the topic /magellan_proflex500_driver/marker_array.

I used the default setting as was mentioned in issue 1 and issue 7.

Several datasets are OK, except for utbm_robocar_dataset_20190418_roundabout_noimage.bag.

I checked it and find that there is no output from topic /fix, so the prolem should come from nmea_topic_driver, which subscribes /nmea_sentence and publishes /fix (official doc here).

Then I checked the source code of the driver, and found that, in the nmea sentence from /nmea_sentence of utbm_robocar_dataset_20190418_roundabout_noimage.bag, no GGA (I'm not an expert here so idk what it is) was provided, so the programe would not go to the line which publishes /fix.

There is also an option use_RMC to publish /fix using the so-called RMC (again, I'm not an expert here so idk what it is), see this line.
But the default setting turns such an option off.

Best,
Xingyu