PakledHostage

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

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Figaro Global Navigation Satellite System

What if Kerbals couldn’t just reach into the fabric of their universe to determine their position? What if, like us, they needed to develop technology to measure their position with any certainty?

The Kerbal Space Program forum’s “KARPA GPS Challenge†thread gave me the idea to develop an actual working GPS plugin for the game. The result is a plugin that works the same way that the real global navigation satellite systems do! It calculates your vessel’s position by measuring distance to GPS satellites in known positions in orbit.

Now you can Launch your own Global Navigation Satellite System (GNSS) constellation, and then start using your own working GPS network by adding the GPS receiver module to any part in your spacecraft!

INSTALLATION

Download the module from Curse.com

The download file contains three folders. The two important ones are:

Parts – Contains the FigaroReceiver directory. The FigaroReceiver directory contains the receiver part. Copy this directory to your KSP\Parts\ directory.

Plugins – Contains the KerblGPS module (KerbalGPS.dll). Copy this file into your KSP\Plugins\ directory.

The “Sources†folder is included per the KSP add-on module distribution policy. Most users can ignore the contents of this directory. It can safely be deleted.

HOW TO USE

Launch a constellation of satellites. They should be well distributed around the globe. Ideally, there should be a minimum of four satellites visible from any point on the entire surface of Kerbin at all times. The higher you place your satellites in orbit, the fewer satellites you'll need to launch and maintain.

Each of the satellites in your GNSS constellation must have a GNSS transmitter part installed or they won't be detected by the Figaro receiver. Mount the transmitter part on single purpose, or on multi-purpose satellites.

Add the Figaro GNSS receiver part to your spacecraft to start navigating using your GPS network.

ACKNOWLEDGEMENTS

Special thanks to MrPwner for providing the Figaro Receiver and Figaro Transmitter part’s 3D models. His artwork greatly improves the aesthetics and user friendliness of this mod.

Special thanks as well to m4v for his help troubleshooting and beta testing version 1.0.22.01 of the mod.

QUESTIONS & ANSWERS

Q: Does version 1.0.23.01 of the plugin work with v1.0 of the game?

A: Reports from users are that it does work in v1.0 of the game. If you encounter a problem with this mod in v1.0 of the game however, please post a detailed description of the issue you've encountered in this thread. I read this thread regularly and will investigate.

Q: Do you plan to add support for contracts?

A: Yes. My goal is to eventually develop a contract class for the plugin. Some users have already made suggestions, on page 18 of this thread, as to what the contract's requirements should be. Feel free to add more.

Q: Can I use/display the latitude and longitude data calculated by my Figaro Receiver in other mods?

A: The short answer is: Only if the other mod's developer implements it in their mod. The plugin exposes Lat, Lon, number of visible satellites and DOP for other plugins to access. Those other plugins must be coded to use that information in some way, however. An example of a mod that has been adapted to work together with Figaro receivers is SirJodelstein's Persistent Trails mod.

Q: What orbits should I use for my GNSS satellite constellation?

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.

Wikipedia's Global Positioning System article has a cool gif showing how the number of GPS satellites that are visible from a given point on the Earth's surface changes with time:

ConstellationGPS.gif

Q: I've launched a satellite network but I still don't get any fixes. Why not?

A: You need a minimum of 4 satellites to be visible above the horizon to get a fix, and all satellites must have the Figaro Transmitter part installed. You could get a fix with just three satellites if the solver were to make an assumption about your vessel's altitude, but I haven't implemented this because I want the system to work at a range of elevations, from sea level to orbit. And while it is true that I could use the altitude information from the game's UI to make a good guess about your vessel's altitude when solving for position with only three visible satellites, I have chosen not to do so.

Q: I've launched a satellite constellation and I have confirmed from the map view that more than 4 satellites are visible to my receiver, but I still don't get a GPS fix. Why not?

A: Every satellite in your GNSS constellation must have a Figaro Transmitter part installed.

Q: I have a slow computer, and I find that the plugin bogs my computer down since you added the new Figaro Transmitter part. Can I revert to using the old method of giving satellites in my network a unique acronym?

A: The plugin maintains a list of spacecraft in your GNSS network that is only updated whenever the number of vessels changes. The module should not add much computational overhead over previous versions of the plugin.

If you do have problems with computer speed, you can try reverting to the old method of identifying satellites in your constellation by means of a unique acronym. Just edit the FigaroReceiver part’s Part.cfg file. You will find a “GNSSacronym†parameter there. By default, it is set to "NONE". You can change it to anything you like. The plugin will then search for satellites with that name, rather than satellites that contain the Figaro Transmitter part.

Q: How do I know how many satellites are visible to my receiver?

A: The number of visible satellites is shown on the Figaro receiver's "Status" UI.

Q: Can I close the Figaro Receiver’s UI window when I am not using it?

A: Yes. You can use the game’s right-click menu or action groups to turn the UI on and off. Right-click on the Figaro receiver part to display the action menu.

odL6Ppd.png

Q: I am having some trouble getting my satellites into the same orbital plane and evenly spaced around the same orbit. Do you have any tips for how to do this?

A: One option may be to emulate the ESA's method of launching their Galileo GNSS satellites. The Galileo system's In-Orbit validation (IOV) satellites were launched two at a time. If you do this, all satellites on any given booster will start out in the same orbital plane. You'll need only to space them out evenly. I launched three satellites at a time aboard my PEZ launch system. The video below shows the PEZ-C launch.

Q: Why are my position fixes erratic sometimes?

A: The module calculates your Figaro receiver's position using a method called trilateration. Like with real GNSS systems, the accuracy of the fix is dependent on the geometry of the visible constellation of satellites. The accuracy of your fix may change quickly if satellites are close together or if they are moving quickly in low orbits.

Q: Why do you seem to use the acronyms "GPS" and "GNSS" interchangeably?

A: I recognise that the American GPS system, like the Russian GLONASS system and the proposed European Galileo system, are specific examples of global navigation satellite systems. I use the terms somewhat interchangeably however, because I believe that most people are more familiar with the acronym “GPS†than they are with “GNSSâ€Â.

Q: Accurate navigation requires accurate position measurements. What methods are available for measuring position if you can't "reach into the fabric of your universe" to establish an accurate position?

A: One option is an Inertial measurement unit (IMU). IMUs "add up" the entire history of accelerations and rotations to estimate position. These tend to accumulate error over time. The accumulation of error is aggravated by things like vibration. Accumulated IMU error can be corrected with external references, such as celestial navigation, ground radar measurements, etc.

NASA has provided an interesting description of how flight controllers navigate the Cassini probe, on their Cassini Mission Overview web page.

oFCF86l.png

This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.

Edited by PakledHostage
Updated thread title to indicate support for v1.0 of the game

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In this mod's old forum thread, TheSec asked a good question about how I spaced my satellites out in the PEZ-C video above. This was my answer:

Could you please explain the numbers a bit behind this ?

Trying to be as brief as possible, I'll do this in point form:

1. I used a 1588 km circular orbit for my satellites because that gives them an orbital period of 1/2 Kerbin's solar day. Kerbin's solar day (not to be confused with its period of rotation) is 6 hours and 50.8 seconds long.

2. The 1088 km x 1588 km transfer orbit has an orbital period 5/6 as long as the 1588 km circular orbit. A spacecraft in the transfer orbit will make 6 orbits for every 5 orbits that a satellite in the 1588 km circular orbit makes.

3. Imagine that two satellites start in the same place, one in a 1088 km x 1588 km transfer orbit and the other in a 1588 km circular orbit. After 1 orbit, the satellite in the transfer orbit will be 1/6 of an orbit further ahead of a satellite in the circular orbit. After 2 orbits, it will be 2/6 of an orbit further ahead. After 5 orbits, it will be 5/6 orbits further ahead. It will meet up again after 6 orbits. 1/6 of an orbit is 60°.

4. The delta-V requirements to transition from the 1088 km x 1588 km transfer orbit into the 1588 km circular service orbit are given by equation (3) below (it may look daunting, but it is really just "plug and chug"... plug the numbers into the formula and chug through the calculation):

90wgOca.png

Note: The terms G M in the equation above are often combined into a single standard gravitational parameter (µ). For Kerbin, µ = 3.530394E+12 m^3/sec^2

Edited by PakledHostage

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I just would like you to know that I love this mod and use it in a way that makes it it almost essential to my gameplay. I navigate using this mod and plan "supply drop zones" , which requires me to maintain an accurate gps network. I made a network for the mun, which caused me to design a launch vehicle that could carry and deploy all 24 GPS satellites (accuracy ranges from .1 to 1m with the occasional spaz where the accuracy drops to 1km for a few seconds). The launch vehicle would definitely help getting this mod working on other planets. Currently I just have this mod set up for kerbin and the mun:

xuttAGWl.png

I would love to see an arrow that points me in the right direction, though. Completely unnecessary, but would be a nice feature. Keep up the good work!

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@frozenbacon: That's awesome! You've got a couple of very tidy constellations. Glad to hear that you're enjoying the mod.

I will think about how to implement an arrow display but I am a quite busy this spring with life outside of KSP and may not get it done for some time. In the mean time, the nav-ball together with the UI's destination window should work. The heading displayed in the destination window is the heading from your current location to the waypoint, along a great circle. The heading will change as you fly towards your coordinate, but if you track the displayed heading, you will be following the shortest route.

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In this mod's old forum thread, TheSec asked a good question about how I spaced my satellites out in the PEZ-C video above. This was my answer:

1. I used a 1588 km circular orbit for my satellites because that gives them an orbital period of 1/2 Kerbin's solar day. Kerbin's solar day (not to be confused with its period of rotation) is 6 hours and 50.8 seconds long.

I have a few questions. Your explanation above helps a lot (and provides insight in a solution I didn't know before), but a few details elude me.

- What is the difference between a solar day and the rotational period?

- According to Wikipedia the solar day of earth varies, depending on the time of the year. Is this different (.ie stable) on Kerbin?

- What is the reason for choosing an orbital period of half a solar day?

- Also, I would like to know how you time the orbits and know when to burn to maintain exact spacing, since there are no fixed points that I know of.

You are really putting the science in KSP :) Thanks a bunch!

Edited by Camacha

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I have my GPS network around Kerbin, it works fine. But With kethane mod and ISA mp mod its also usable to use those for navigation. With that mapping mod you just once map a planet or moon and then use it as a "gps" which is kinda shame that I dont have use for this mod anymore. :X

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I have a few questions

- What is the difference between a solar day and the rotational period?

A solar day is what we colloquially call a "day". It is the length of time between high noon (transit) on two successive days. On Earth, the length of the solar day varies by ± a few seconds throughout the year because the Earth's orbit is elliptical and because the Earth’s axis of rotation is tilted relative to its orbital plane.

Our mean solar day is 24 hours long, while the Earth's rotational period (sidereal day) is 23 hours, 56 minutes and 4 (and a bit) seconds long. During the 23 hours, 56 minutes and 4 seconds that it takes the Earth to spin around once, it also moves about 1 degree along its orbit about the Sun.

siderealsolarday.jpg

Ref: Durham University's Solar Days and Sidereal Days page

Kerbin's solar day is 6 hours and 50.8 seconds long, while its sidereal day (rotational period) is 6 hours long. You can prove this to yourself by watching successive Kerbol rises from the launch pad. The amount of time between Kerbol rises, as viewed from the pad is 6 hours and 50.8 seconds.

- According to Wikipedia the solar day of earth varies, depending on the time of the year. Is this different (.ie stable) on Kerbin?

As mentioned above, the length of the solar day varies by ± a few seconds throughout the year because our orbit about the Sun is elliptical and because the Earth’s axis of rotation is tilted relative to our orbital plane. We reach perihelion in early January and aphelion in early July. The elliptical orbit causes a variation in angular speed throughout the year. That variation in angular speed, in part, causes the Sun to drift east-west in the sky. (The Sun's east-west motion is also partially due to a complex geometric effect of the Earth's axial tilt). In addition to the east-west motion, the Earth's axial tilt also causes the Sun to appear to move north-south in the sky during the year. The combined effect of the Earth’s axial tilt and elliptical orbit results in the analemma. Here's a famous photo showing the Sun's analemma, taken by Dennis di Cicco:

3001422.jpg

Kerbin does not have an axial tilt and its orbit is circular, so the length of its solar day does not vary throughout the year.

- What is the reason for choosing an orbital period of half a solar day?

I don’t actually know. I suspect that the GPS satellite’s orbits were chosen for practical engineering reasons, rather than any physical reason. If anyone does know (and better yet, can provide a reference) please let us know.

The Wikipedia Global Positioning System article says that the orbital period was chosen because it results in every satellite following a consistent ground track and being visible from any point on the Earth at least twice a day. This is important because every satellite’s orbit must constantly be characterised via measurements from a limited number of ground stations to allow the system to maintain any degree of precision. The FAA has a good website that describes how the GPS system works, including a page that describes how the GPS control segment tracks and maintains the accuracy of the satellite position information. The SV position information is downlinked via the GPS signal and is used by your GPS receiver when calculating position fixes.

The Wikipedia article also says that each satellite makes two complete orbits each sidereal day, rather than each solar day. This contradicts what I have read elsewhere, but it makes sense when I think about it in the context of the above paragraph.

- Also, I would like to know how you time the orbits and know when to burn to maintain exact spacing, since there are no fixed points that I know of.

Exact spacing doesn’t seem to matter very much. What matters is that at least 4 satellites are visible from any location at any time.

@elkar: I am glad to read that you were able to construct a working GPS constellation. Hopefully you had fun doing it. Thanks for sharing that the ISA map mod includes a navigation feature. Presumably that mod implements some advanced technology that exceeds our own? I am not aware of any automated navigation technology that uses a map of a celestial body to determine position. Presumably it would utilise some sort of image recognition to correlate what the system "sees" with a map? That makes the ISA map mod different than this mod. This GPS mod allows players to implement and learn something about an existing real-world technology, rather than to implement some futuristic and yet to be invented system.

Edited by PakledHostage

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A solar day is what we colloquially call a "day". It is the length of time between high noon (transit) on two successive days. On Earth, the length of the solar day varies throughout the year because the Earth's orbit is elliptical and because the Earth’s axis of rotation is tilted relative to its orbital plane.

That made that a lot clearer, thanks! I overlooked the slight shift in earth's position around the sun influencing the day period as perceived from a fixed position on earth.

I don’t actually know. I suspect that the GPS satellite’s orbits were chosen for practical engineering reasons, rather than any physical reason. The Wikipedia Global Positioning System article says that the orbital period was chosen because it results in every satellite being visible from any point on the Earth at least twice a day. This is important because every satellite’s orbit must constantly be characterised via measurements from a limited number of ground stations to allow the system to maintain any degree of precision.

That sounds quite plausible. Not really a factor in KSP, but in real life keeping your satellites/clocks up to date is essential, of course.

Exact spacing doesn’t seem to matter very much. What matters is that at least 4 satellites are visible from any location at any time.

I later realized that one could calculate the orbit times and use the KSP mission timer to space out the satellites pretty much dead on. I think that must be an approximation of how they do it in real life too, which is somewhat of a concern to me. Maybe not essential for proper operation, but something that scratches my OCD itches :cool:

@elkar: I am glad to read that you were able to construct a working GPS constellation. Hopefully you had fun doing it. Thanks for sharing that the ISA map mod includes a navigation feature. Presumably that mod implements some advanced technology that exceeds our own? I am not aware of any navigation technology that uses a map of a celestial body to determine position. Presumably it would utilise some sort of image recognition to correlate what the system "sees" with a map. That makes the ISA map mod different than this mod. This GPS mod allows players to implement and learn something about an existing real-world technology, rather than to implement some futuristic and yet to be invented system.

Actually, I think there is military technology used in cruise missiles that works in such a way when necessary. I dug into that a little bit and these missiles are guided by different, often redundant sysems. The well known Tomahawk uses four; GPS, DSMAC, TERCOM and IGS.

- GPS we all know and love, though the military variety is a bit more accurate.

- IGS (Inertia Guidance System) is, for as far as I know, used in a lot of space craft too but called INS. It just measures all the forces and calculates the corresponding position. Major disadvantage is that errors tend to accumulate over time, so as a stand alone device it might not be ideal.

- TERCOM (Terrain Contour Matching) uses radar data matched to a 3D map to position itself. I think this is what makes it capable of low level flight.

- DSMAC (Digital Scene Matching Area Correlation) is somewhat similar, though it is optical. I believe this is only used for final target acquisition and comes in handy when targeting something moving.

Of course, that is just some outdated technology we know about. Some way more advanced gadgets are probably killing unsuspecting suspects around the world :)

I also could image that you could use some funky triangulation when you are , for example, on the earth side of the moon. Using signals from satellites or ground stations it should be possible for an orbiter or ground vehicle to roughly determine its position. Using something like ground radar and know previous positions even less than three signals might suffice. Remember that ISA isn't very accurate either :) Of course this all is not quite up to GPS standards, but I can imagine it being more practical when on interplanetary missions where GPS is simply not available or financially feasible.

An orbiter that scans the surface optically and/or differently and relays positional information to a lander, perhaps aided by a signal from said lander seems plausible using know technology. Of course, current missions don't move around the surface enough to warrant such technology - Mars landers are visually checked upon - but I do not see any reason it would or could not work. Even guidance by meansof a stored on the surface seems plausible, though some problems might arise from atmospheric changes on planets like Mars.

All said and done, your mod does add a lot of realism and fun, so no reason not to use it!

Edited by Camacha

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Actually, I think there is military technology used in cruise missiles that works in such a way when necessary. I dug into that a little bit and these missiles are guided by different, often redundant sysems. The well known Tomahawk uses four; GPS, DSMAC, TERCOM and IGS.

- GPS we all know and love, though the military variety is a bit more accurate.

- IGS (Inertia Guidance System) is, for as far as I know, used in a lot of space craft too but called INS. It just measures all the forces and calculates the corresponding position. Major disadvantage is that errors tend to accumulate over time, so as a stand alone device it might not be ideal.

- TERCOM (Terrain Contour Matching) uses radar data matched to a 3D map to position itself. I think this is what makes it capable of low level flight.

- DSMAC (Digital Scene Matching Area Correlation) is somewhat similar, though it is optical. I believe this is only used for final target acquisition and comes in handy when targeting something moving.

I forgot about TERCOM and DSMAC... Thanks for the reminder. There's a good article on JPL's Cassini site that describes how Cassini probe is navigated. Among the methods that they use are doppler shift, ranging tones and optical navigation (celestial navigation) to verify and correct accumulated error in the inertial navigation systems.

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Would you mind if I created a modified version of this, which requires a 'GPS transmitter' module installed on each satellite instead of 'GPS' in the name? (It just seems more realistic to me)

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I'd rather you didn't, but you can go ahead if it is for your own use only. Do not post your modification on SpacePort or otherwise distribute it, however.

What you are talking about amounts to adding a few lines of code and maybe adding a 3D model for the transmitter part. That isn't enough to justify having two versions of this mod floating around.

If there's enough interest in your suggestion, then maybe I will add it to the plugin. In that case, I will of course credit you for the idea.

Thank you for asking.

Edited by PakledHostage

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How high should i put my satellites?

There's no "right answer". You can put them wherever you want, but putting them into higher orbits means that fewer satellites are required to maintain complete coverage. The equation for the percentage of Kerbin's surface that is visible to a satellite at a given orbital altitude reduces to quite a simple relationship:

czmFaPM.png

Here's a table of percentage of Kerbin's surface over which a satellite can be seen, at different orbital altitudes:

3000 km altitude -> 41.7%

1500 km altitude -> 35.7%

1000 km altitude -> 31.3%

500 km altitude -> 22.7%

100 km altitude -> 7.1%

70 km altitude -> 5.2%

Note: Visible in this case = at or above the horizon, not taking into account atmospheric refraction.

Clearly there's an advantage to placing your satellites in higher orbits but as discussed on the previous page, other factors also come into consideration when choosing a service altitude for your satellites. Some real-world considerations are cost of the launch vehicles, ability to track and update the satellite's orbital elements on a regular basis, the geometry of the resulting constellation, etc.

Edited by PakledHostage

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I love it! Great work!

One question: on the previous page you said that a 1088 km x 1588 km transfer orbit has a 5/6 orbital period of a 1588 circular orbit and some formulas to calculate the transfer delta-v requirements. But how did you calculate that a 1088kmx1588km orbit is 5/6 of the orbital period of 1588kmx1588km?

I ask because I would like to calculate an orbit with a 1/3 orbital period of a different circular orbit.

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One question: on the previous page you said that a 1088 km x 1588 km transfer orbit has a 5/6 orbital period of a 1588 circular orbit and some formulas to calculate the transfer delta-v requirements. But how did you calculate that a 1088kmx1588km orbit is 5/6 of the orbital period of 1588kmx1588km?

RIjpgMW.png

Write one equation for orbital period in terms of your circular orbit ( i.e. altp and alta = altitude of your circular orbit ).

Write another equation for orbital period in terms of your unknown Pe. Ap (i.e. alta ) in this second equation is equal to the altitude of your circular orbit.

The orbital period of the second equation is 1/3 of the orbital period for the first. Therefore three times the second equals the first. Multiply the second equation by 3 and equate the two equations, then solve for Pe.

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In your video you say:

"Insertion into transfer orbit having 6:5 orbital resonance with final orbit"

What does that mean?

Like having a 1000x1588 orbit and then decouple one satellite every 1 hour?

Edited by zYnthethicz

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In your video you say:

"Insertion into transfer orbit having 6:5 orbital resonance with final orbit"

What does that mean?

It means an object in one orbit goes around 6 times for every 5 times that an object in the final orbit goes around. Please see this post for more about this.

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It means an object in one orbit goes around 6 times for every 5 times that an object in the final orbit goes around. Please see this post for more about this.

Ah, now i get it. Thanks.

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RIjpgMW.png

Write one equation for orbital period in terms of your circular orbit ( i.e. altp and alta = altitude of your circular orbit ).

Write another equation for orbital period in terms of your unknown Pe. Ap (i.e. alta ) in this second equation is equal to the altitude of your circular orbit.

The orbital period of the second equation is 1/3 of the orbital period for the first. Therefore three times the second equals the first. Multiply the second equation by 3 and equate the two equations, then solve for Pe.

Thanks! That helped me a lot! :) Did some of the equations today. :P

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Would you mind if I created a modified version of this, which requires a 'GPS transmitter' module installed on each satellite instead of 'GPS' in the name? (It just seems more realistic to me)
... If there's enough interest in your suggestion, then maybe I will add it to the plugin. ...

I second the request.

... The equation for the percentage of Kerbin's surface that is visible to a satellite at a given orbital altitude reduces to quite a simple relationship ...

Do you have a reference for that? I was looking for that information, and would like to read more about it. Thanks!

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Do you have a reference for that? I was looking for that information, and would like to read more about it. Thanks!

I don't have a reference but you can work it out with a bit of high school trigonometry and algebra. That's how I did it. The angle to the horizon from a given orbital altitude can be computed with simple trig. That value gives you the height of the spherical cap that forms the visible surface. The percentage area of Kerbin's surface that you can see, from horizon to horizon, is just the surface area of that spherical cap divided by the surface area of the entire sphere. There are lots of references online that will give you the equations for the surface area of a sphere and the surface area of a spherical cap.

Ialdabaoth's idea is a good one, but I don't see any point in implementing it just yet. It is his idea and I'd need his permission, plus it adds computational overhead to the module. This game already runs slow on lots of people's computers. Every straw, on its own, isn't a significant load but together they all add to the burden. For now, I figure players can self-regulate. If they want to launch GNSS satellites that don't have any antennas, they are only cheating themselves. It is a single player game, after all...

Edited by PakledHostage

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I'm not really good at math D: as well as launching stuff into very high orbits *shakes fist at fuel consumption*, but... correct me if I'm wrong... if I were to set my satellites at 100km orbits, I would need around 20 satellites for a full GPS coverage, correct? Also what would their orbit º angle variation would be? or rather, have to be?

Apologies and Thanks in advance for the dumb questions/very helpful answers :P

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I'm not really good at math D: as well as launching stuff into very high orbits *shakes fist at fuel consumption*, but... correct me if I'm wrong... if I were to set my satellites at 100km orbits, I would need around 20 satellites for a full GPS coverage, correct? Also what would their orbit º angle variation would be? or rather, have to be?

Apologies and Thanks in advance for the dumb questions/very helpful answers :P

100km sounds extrodinarily low an fast orbiting for a sattilite. I put my station at 180km and keosync sats at 2,864 km high - which is practicall half way to the mun. A semi sync constellation of greater than 1,000km would be easier than trying to put enough satilites down at just 100km as each one would lose contact in less than 5 minutes rather than 5 hours.

What kind of launchers/sattilite combinations are you running an on what kind of gravity turn?

3 probe fuel tanks and 2 orange radial rockets or probe engine would suffice is pushing it up to medium orbit from low. Together that is only like 2 mass more to add.

Edited by Read have Read

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Ok so I should put my sats at 1000 km... I'll have to give that a try. As far as positioning, how exactly do you do that? do you just launch sat after sat at 45 degrees from each other? say, 0, 45, 90, etc?

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