Using the new GPS module
bigkahuna from United States  [14 posts]
14 year
I'm planning an autonomous boat project and am considering using RoboRealm for the guidance system using the new GPS Reader module, and have a few questions:

1.  Is there any info or a tutorial on how to use the Path Planning module with the GPS Reader module?

2.  Any example scripts showing how to use the SetArrayVariable function with RR?

3.  Anyone else using the GPS Reader to navigate their robots?  Any advice to share?

I also plan on adding a digital compass via the Serial Port module to avoid heading errors that occur when the boat is moving slowly or not at all.  Anyone else work with digital compasses and RR?

 [29 posts] 14 year
I have not used the GPS module in RR. However, my experience with digital compass (HB-55) from Parallax inc. suggests that you need to consider averaging all your heading data. Especially if you are using an RC or small boat that will drift, pitch, and roll while waterborne. When using both GPS and digital compass, you can average the two headings to approximate your current direction. Digital compass readings are unreliable during ANY roll or pitch and assumes you are stable in the X axis. Good luck.
bigkahuna from United States  [14 posts] 14 year
I won't be using the GPS for heading info, only the digital compass.  I plan on using GPS info for course to next waypoint, distance from waypoint, etc.  The compass I'm using is tilt compensated, so that won't be an issue either.
Anonymous 14 year
1. Path Planning - You would probably not use these two modules together as the path planning assume you have the entire course in view (i.e. ceiling mounted camera). The GPS module is has the path planning within it in the sense of setting waypoints, moving towards the way point (see GPS_WAYPOINT_HEADING variable) will eliminate that one from the course in the same way the path planning using waypoints. Thus using the GPS module would not require the path_planning module. The GPS being satellite based whereas the path planning being visual based.

2. SetArrayVariable

list = GetArrayVariable("BLOBS")

if isArray(list) and ubound(list) > 0 then

  list(1) = 100.0
  SetArrayVariable "BLOBS", list

end if

or are you looking for something more specific to your project?

3. GPS advice? - Not as accurate as we'd like so using a compass in conjunction with the GPS would be ideal. Most entrants in the Sparkfun AVC contest uses this technique. GPS for global nav, compass for immediate direction.

Mano from Netherlands  [27 posts] 13 year
So is it at all possible to use compass data in RR?
Anonymous 13 year
Do you mean from the GPS or from a compass device? For a compass device you'd need to hook up the serial module (assuming the device is serial) to read its values. Should be straightfoward to get a sequence of characters to read in the heading value.

If you have a compass and are having issues on getting the data from it post the data that it does send over serial and we can help with the parsing sequence in the serial module.

Mano from Netherlands  [27 posts] 13 year
I accually meant to say that i want the "compass" data to be used by roborealm instead of the normal used "GPS" heading, in the gps reader plugin.

Since the gps is not at all accurate with heading in low speeds, i want the compass that is connected to my microcontroller ( send data via serial to RR), to be used by the gps reader.
Anonymous 13 year

Ok, I think we are starting to understand what you are asking for. Lets say there was a variable that RoboRealm has from the compass and that it could feed that into the GPS module .... the question we have now is what does that help with? The only place that the course direction is used is in displaying the robot graphic. Is that what you'd want to come from the compass instead? Or should the GPS location coordinates also be ignored and overridden by the compass data? But the compass only gives direction and not distance ... which would need to come from the noisy GPS.

If you have some thoughts about how the information is used we can add a variable source to the GPS module that would then have access with that information. We're just not sure what you'd do with it even if you had it.


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