[1.0] Figaro Global Navigation Satellite System - Launch a Working GPS System

[ZaPPPa]

Hmm.. A Canadian with knowledge of GNSS and IMU's... You work for Novatel by any chance?

[PakledHostage]

@ZaPPPa: Welcome to the forums! I responded to your question by PM.

[Camacha]

UPDATE

– Exposed some variables in the plugin to allow in-game integration with other mods such as SirJodelstein's Persistent-Trails plugin.

Does this mean potential compatibilty with kOS? I know kOS has done the same, but with exposed variables/things on both ends still nothing happens, I guess.

Edited December 18, 2013 by Camacha

[PakledHostage]

I've exposed some variables but the functionality would need to be coded into whatever plugin you want to use with your GPS. SirJodelstein contacted me and asked if I could expose the number of visible satellites so that he could use that value to enable/disable logging of persistent trails, depending on whether or not a GPS signal was available. I guess this was something that his users were asking for, so he implemented it as a "hardcore" mode.

[Camacha]

Ah, that is unfortunate. I was hoping to use this for my kOS vehicles, as having some magic location just it not the same. For space vehicles I can live with the idea that the initial orbital probe I always send simply does a visual confirmation of rover location, with the rover possibly combining local landscape data with radar/height maps. For Kerbin I would like to do something a bit more elaborate though.

It would be a decent exercise before I start a quadcopter project in real life too.

[permanentlytemporary]

Integration with the new Toolbar would be great if you've got the time and willingness!

Also, other than giving players the ability to create a working GPS system, what's the functionality of this mod? What happens when you can't get a GPS fix, does map view not show where you are? You lose control if you don't have a connection in RemoteTech - does this do something similar?

[Kimberly]

Also, other than giving players the ability to create a working GPS system, what's the functionality of this mod? What happens when you can't get a GPS fix, does map view not show where you are? You lose control if you don't have a connection in RemoteTech - does this do something similar?

If you can't get a GPS fix, you won't know your coordinates and won't be able to have the GPS system direct you towards the coordinates you want to go. Map view is unaffected, though.

[dlrk]

What's the right altitude/spacing for 10x resize/RSS?

[PakledHostage]

What's the right altitude/spacing for 10x resize/RSS?

I'm afraid that I don't understand the question?

[cakepie]

What's the right altitude/spacing for 10x resize/RSS?

There are no exact altitude / spacing requirements, all that matters is that you'd want at least 4 satellites to be visible (i.e. above the horizon) at any time from any location on the planet.

(*1) 4 visible satellites is the bare minimum; with additional satellites the accuracy of the position calculated by GPS will improve (with diminishing returns as you increase the number of satellites).

(*2) In general, most people want pretty good coverage across the whole planet. But if, say, you don't need coverage in the polar regions (or will settle for poorer accuracy) you could reduce the number of satellites needed.

If you're using resized universe mods, the good news is that the coverage of a satellite constellation over the surface of a planet is purely a function of the planet's radius, so you just need to scale accordingly.

So, for example, if you already have a constellation altitude/spacing setup that works for stock Kerbin and you want to achieve the same coverage for 10x Kerbin, you just need to scale the altitude by 10x as well.

(Note that although coverage is unchanged, orbital frequency with respect to the planet is not guaranteed to be preserved as that also depends on planet mass. E.g. synchronous orbit in stock may no longer be synchronous when scaled up.)

If you have no prior experience with this GPS mod, I suggest you look to the Q&A section in OP for suggestions re: stock Kerbin and scale accordingly.

I'm afraid that I don't understand the question?

Refers to the real solar system mod / 10x scale variant

[ZaPPPa]

The nice thing about the real GPS system is that the orbit time is close to 12h. In my line of work this is useful because we can do tests on two different days and get approximately the same GPS constellation at the same time of day. For our very high speed, high accuracy requirements, this means we can do better comparisons of data and have 24h of time between tests to tweak and develop.

Warning: Be aware that 10x Kerbin has a default Kerbal rotation of 6 hours, which means that the GEO orbit will be very low. When I tinkered with 10x Kerbin I changed the rotational period to 18 hours, which made the game a bit harder (takes more deltaV to reach the same altitude because your initial orbital velocity is lower due to slower rotation).

Real GPS orbit is about 20K Km. At 10x Kerbin with 18h rotation GEO became about 27.5K Km, so I'd put them at 13K-ish.

To get guaranteed coverage of at least four visible satellites, you'll probably need four planes with four satellites each. Then you can space them our at 90 degrees in the orbital plane and space the planes out by 45 degrees each (6 hour launch increments on a 24h day if you put them in 1/2 GEO = MEO orbit)

Edited January 6, 2014 by ZaPPPa

[cakepie]

Integration with the new Toolbar would be great if you've got the time and willingness!

So, since I had a bit of time, and source code was included CC-BY-NC-SA, I went ahead started messing around with it to see how to go about doing this...

...and ended up getting carried away, so now I have a dev build that fixes/adds a bunch of things -- changes include:

- Added persistence: now remembers on/off state, destination inputs and GUI window mode/position/size; this is on a per part (receiver) basis

- Fixed GUI handling: GUI visibility now works properly when staging, docking/undocking or switching between craft in flight -- no need to deactivate and reactivate

- Streamlined loading and initialization (hopefully doesn't break this previous fix!)

- Fixed destination mode "here" button failing to set N/S & E/W values.

- Clears field values (displayed in receiver part's right click menu) upon deactivation.

- Add (optional) support for Blizzy78's toolbar mod (via separate KerbalGPS_Toolbar.dll)

-- button color indicates if none/some/all GPS receivers on a vessel are on

-- clicking will activate/deactivate all GPS receivers on the vessel

PakledHostage, I'll PM you with a link where you can grab my code/build. If you're amenable to it, we can make my build available for other users to test (probably a good idea) before officially pushing the changes back into the mod release.

Edit: just added ability to display the destination heading on the navball

Edited January 8, 2014 by cake>pie

[Mecripp]

The nice thing about the real GPS system is that the orbit time is close to 12h. In my line of work this is useful because we can do tests on two different days and get approximately the same GPS constellation at the same time of day. For our very high speed, high accuracy requirements, this means we can do better comparisons of data and have 24h of time between tests to tweak and develop.

Warning: Be aware that 10x Kerbin has a default Kerbal rotation of 6 hours, which means that the GEO orbit will be very low. When I tinkered with 10x Kerbin I changed the rotational period to 18 hours, which made the game a bit harder (takes more deltaV to reach the same altitude because your initial orbital velocity is lower due to slower rotation).

Real GPS orbit is about 20K Km. At 10x Kerbin with 18h rotation GEO became about 27.5K Km, so I'd put them at 13K-ish.

To get guaranteed coverage of at least four visible satellites, you'll probably need four planes with four satellites each. Then you can space them our at 90 degrees in the orbital plane and space the planes out by 45 degrees each (6 hour launch increments on a 24h day if you put them in 1/2 GEO = MEO orbit)

A: The geometry of your constellation doesn't need to be super precise. You just want your satellites to be well distributed around the globe. Real world GPS satellites are in circular orbits with an orbital period of 12 hours (half the Earth's mean solar day). They are located in 6 orbital planes, spaced 60º apart and inclined at 55º from the equator. The Kerbin equivalent orbital period would be 3 hours and 25 seconds (because Kerbin's solar day is 6 hours and 50 seconds long). A 1588 km high circular orbit has about the right orbital period. You can achieve the 60 degree spacing between orbits by launching at 1 hour intervals.

I maybe wrong but sounds like you are saying kerbin is scale to earth when it isn't ?

At (Real GPS orbit is about 20K Km. At 10x Kerbin with 18h rotation GEO became about 27.5K Km, so I'd put them at 13K-ish.) your not in space or am, I misreading that ?

Edited January 11, 2014 by Mecripp2

[Camaron]

I'm really interested in trying out this mod, but it looks very complex and I don't want to burn hours doing something stupid incorrectly, like whoever inspired the Q/A response explaining that GPS satellites need the transmitter. Whoever asked that question probably ate a whole day over that. So here's my top question right now.

Somewhere it is mentioned that getting this network over Kerbin doesn't help you much over extreme ranges, like to other planets. I also saw an image early in the thread which showed both Kerbin and The Mun with their own networks completed. Is there some kind of accuracy degeneration over long ranges? If I have a full Kerbin Network completed and have total accuracy around kerbin, how far out before the signal degenerates? Is there a maximum amount of accuracy degeneration?

[m4v]

Somewhere it is mentioned that getting this network over Kerbin doesn't help you much over extreme ranges, like to other planets. I also saw an image early in the thread which showed both Kerbin and The Mun with their own networks completed. Is there some kind of accuracy degeneration over long ranges? If I have a full Kerbin Network completed and have total accuracy around kerbin, how far out before the signal degenerates? Is there a maximum amount of accuracy degeneration?

I don't understand very well the question, you mean if placing a GPS network in a very high orbit will affect accuracy?Then in that case distances doesn't affect accuracy, what affects accuracy is the distribution and quantity of sats, if two sats get too close together then you lose accuracy, also this is mostly near the surface of the planet, I don't know with ships in orbit, only that if you are in a orbit higher than your sats then you won't get any locks (something I discovered when I tried to place ground transmitters)

[reschke]

Somewhere it is mentioned that getting this network over Kerbin doesn't help you much over extreme ranges, like to other planets. I also saw an image early in the thread which showed both Kerbin and The Mun with their own networks completed. Is there some kind of accuracy degeneration over long ranges? If I have a full Kerbin Network completed and have total accuracy around kerbin, how far out before the signal degenerates? Is there a maximum amount of accuracy degeneration?

If I understand your question correctly you are wondering about GPS accuracy on another planet; say Duna maybe; while using the GPS constellation from Kerbin? It doesn't work that way. You need a GPS constellation around each body in the system that you plan on visiting and if that is the case then you need to build a bunch of probes that have the GPS and ScanSat modules on them so you can get accurate maps and data once you put your kerbonauts on the surface and they start roaming around. In that image your reference with the constellation over the Mun and Kerbin those were only to aid in navigating locally and I seriously doubt they had anything to do with navigation between celestial bodies.

[PakledHostage]

Thanks, everyone, for your help answering user's questions. And to you, cake>pie for your efforts. Feel free to use the changes you made to my mod for your own purposes but please don't distribute it. It does not sound like your derivative work is significantly different from my original project to warrant being its own mod. I will consider incorporating your ideas in a later revision (with appropriate credit given) if there is enough demand from the user base.

And with regard to the accuracy/availability of navigation solutions outside the orbit of the navsat constellation: It is probably because of how the algorithm calculates whether a satellite is located above the horizon or not. I admit that I hadn't actually considered that case when I wrote it. I will fix it in the next update.

P.S. Navigation solutions are intentionally restricted to only work within the same SOI as the navsat constellation. This is for the sake of realism and in keeping with the limitations of existing real-world GNSS technologies.

Edited January 11, 2014 by PakledHostage

[Camaron]

I'll have to fire it up and see for myself what's going on.

I don't seem to get it. If navigation only functions within the same SOI as the existing network, how could I ever visit any other planet? This confusion probably has to do with my own unorthodox and very "wing-it" style of playing the game and navigating the space. My usual strategy is to build tremendously over-capable crafts. I'm pretty sure most people would set up their path well before ever leaving Kerbin orbit, and many more go even farther and automate it with mechjeb.

[cakepie]

(nuke)

Edited April 5, 2018 by cakepie

[reschke]

Camaron,

Long before GPS was working NASA and the Soviet Union Space Program sent probes to other planets (Mars and Venus) before the GPS system was ever being used. Going to other celestial bodies within KSP is not really that hard and doesn't require GPS to do it or even Mechjeb. However if you want to have GPS available on the other planets you will need to put a GPS constellation around that body and that is why I said you could mix in the GPS aspect on a satellite that allows terrain mapping and will help you build up maps and locations on those planets and moons that you want to visit.

[m4v]

I don't seem to get it. If navigation only functions within the same SOI as the existing network, how could I ever visit any other planet?

I believe you're confusing what a GPS is, is a planetary navigation system, you don't plot a course to other planet with it.

[GavinZac]

I believe you're confusing what a GPS is, is a planetary navigation system, you don't plot a course to other planet with it.

In six-seven-three-nine-nine-nine-nine-nine-nine-nine-nine-nine metres, turn left.

[Entropius]

Question for the developer: Have you considered adding a baseline error to simulate atmospheric error, and then making a 2nd satellite antenna to slap onto a geostationary satellite? The principle goal being to recreate not just the core GPS constellation, but also WAAS constellations? Or is this pointless due to some of Kerbin's un-earth-like properties (for example, planet size)?

[PakledHostage]

Question for the developer: Have you considered adding a baseline error to simulate atmospheric error, and then making a 2nd satellite antenna to slap onto a geostationary satellite? The principle goal being to recreate not just the core GPS constellation, but also WAAS constellations?

It is an interesting idea... I need to balance realism with fun, and I am afraid that too much realism would negate some of the fun.

But on the other hand, this mod is intended as a "science mod" in so far as it gets players thinking about where their navigation information comes from. Maybe having an option to improve navigation accuracy using WAAS, EGNOS, GAGAN, etc analogs would further that goal?

What do you readers of this thread think?

[diomedea]

What do you readers of this thread think?

I am all for realism, therefore if you like to implement that WAAS et similar option (and that does not kill performance in KSP, though I can't see why it should), please do. Talking of realism and accuracy, there is however also to consider SPS against PPS, I mean if the accuracy you make in with Figaro is already equivalent to GPS/PPS, there is not much more to add.

Edited March 2, 2014 by diomedea
imoprove wording