Indian Space Programme Discussion

nTripathi · Post by **nTripathi** » 10 Mar 2016 17:14

ranjan.rao wrote: Is it only a software encryption issue or there is some hardware aspect to it. I was wondering how much secure we can keep this service from ChiPakus. If it's just an encryption issues, I am sure it will be a matter of time before they get their hands to it.

There are ways to avoid hacking of military grade signals:
1. Regulate the distribution of military receivers.
2. multiple bit pseudo random P(Y) key to decrypt incoming signals.
3. each receiver with unique P(Y) architecture to identify receiver identity.
4. multiple frequency signals each coupled with its encryption precise (P) code. (IRNSS uses L5 and S bands.)
5. anti-spoofing through periodic change in pseudo random key.
6. ... and many more that i do not know about!

Also, at last, facing treason for military signal jamming or spoofing: so either jailed in isolation for life or hanged... so people dont do it!

SaiK · Post by **SaiK** » 10 Mar 2016 17:41

data encryption in addition to transport layer will do. but that adds processing time overheads, and latency. i guess, not a big delta to worry considering the applications we talking about mid-course missile guidance. btw, a terminal phase anyway can't depend on 20 meter accuracy.

i would think about fleet movements, position aware notifications, metrics on logistics, better ETAs, better integration of traffic controls and management, better motor-assist map based navigation, etc.

mil wise, battlefield management integration, orbats, (must integrate tightly with IFF or the en/decryption key includes IFF keys), logistic support systems, etc. my dashboard at HQ becomes much more drill-down and summarized.

nTripathi · Post by **nTripathi** » 10 Mar 2016 17:59

LokeshC wrote: A KE hit usually changes the orbit of the sattelite (along with doing damage ofcourse), and the debris will usually go from circular to eliptical with microscopic eccentricity (i.e. will be barely even different from the original orbit) and therefore will not impact any other satelite.

I could not find an example of KE hit that did not create debris... Also, such a system would have to be highly controlled and have sub-sonic speeds relative to the target: during this, if satellite detects and manoeuvres, it is not like that weapon-head would come back and chase (fuel constraints).

If there a successful high energy KE hit, there will be fragmentation and the slower fragments will deorbit (very slowly) and the higher velocity fragments will continue in elliptical orbits following approximately the same orbital period. It wont pose a statistically large enough threat for any nearby sattelite.

This is what China created in 2007:

Picture shows the orbits of debris created in chinese test! The white line is the international space station...
This is what happened 6 years later: http://www.space.com/20138-russian-sate ... -junk.html

But this is still not the real problem... the chain reaction that follows: debris->collision with satellites->more debris->more collisions!

JayS · Post by **JayS** » 10 Mar 2016 18:16

Can we make an anti-sattelite weapon which will have surgical precision and would disable the satellite rather than blowing it apart. For example, a small robot thinggy going and attaching itself with the satellite and say fry its electronics, or damage its heat shield or damage its transponders or try and de-orbit it?? Something like that?? I know its quite challenging technologically, but we can do feasibility study at-least using nano/micro satellites.

jayasimha · Post by **jayasimha** » 10 Mar 2016 18:20

gurujis,,,, dint see this being posted..

http://pib.nic.in/newsite/PrintRelease. ... lid=133911

Press Information Bureau
Government of India
Department of Space
23-December-2015 19:31 IST
National Urban Information System

National Urban Information System (NUIS) is the project of Ministry of Urban Development with Survey of India as the focal point. At the behest of Ministry of Urban Development, National Remote Sensing Centre (NRSC) of ISRO has prepared geospatial thematic database (comprising of 12 layers) for 152 towns on 1:10,000 scale and carried out Aerial survey of 132 towns at 1:2,000 scale for Survey of India.

Within one year after the completion of geospatial thematic database, NRSC has hosted the database on Bhuvan Geoportal and developed Bhuvan-NUIS application for enabling formulation of Master Plans by state town planning departments. NRSC has also organised 2 National workshops, 7 Regional Workshops and 25 State level workshops for imparting training on Bhuvan-NUIS to more than 2,000 Town Planning offcials.

The thematic mapping under NUIS was envisaged as a onetime exercise. NRSC has submitted the geospatial thematic database for 152 towns on 1:10,000 scale to Ministry of Urban Development for further use.

The concerned state town planning departments have been authorised to use Bhuvan-NUIS database for master plan formulation. However, the entire database is also made available in the public domain on Bhuvan Geoportal for visualisation.

Under its Disaster Management Programme, ISRO has provided the flood inundation maps using satellite data extensively during the recent floods of Tamil Nadu and Andhra Pradesh.

This information was provided by the Union Minister of State (Independent Charge) Development of North-Eastern Region (DoNER), MoS PMO, Personnel, Public Grievances & Pensions, Atomic Energy and Space, Dr Jitendra Singh in a reply to an unstarred question in Lok Sabha today.

****

KSD/NK/PK/KM

member_22733 · Post by **member_22733** » 10 Mar 2016 19:06

I missed the fact that the satellite itself has enormous kinetic energy. So all one would need is to achieve contact with the satellite with a much lower velocity (or even better, by having a projectile go in the other direction). In that case the fragments will have widely dispersed orbit (seems like what the Chinese have done).

Explosions in space dont do much damage as there is no medium to transmit the pressure wall. The only thing you can do is to fragment a projectile (using conventional explosives) near the satellite and hope some of the fragments hit the sat.

member_23694 · Post by **member_23694** » 10 Mar 2016 20:09

OK congrats.. another PSLV success

However i am more interested to know about the shade which always comes in between the camera and the rocket clearing the launch pad and disrupt rocket's view.

How can DD repeat same mistake again and again in such a flawless ISRO journey in recent past

nTripathi · Post by **nTripathi** » 10 Mar 2016 20:12

nileshjr wrote:Can we make an anti-sattelite weapon which will have surgical precision and would disable the satellite rather than blowing it apart. For example, a small robot thinggy going and attaching itself with the satellite and say fry its electronics, or damage its heat shield or damage its transponders or try and de-orbit it?? Something like that?? I know its quite challenging technologically, but we can do feasibility study at-least using nano/micro satellites.

Those type of satellites are called parasites. I once heard about a programme, most probably backed by China (or maybe US: dont remember), that would release a swarm of parasites into LEO like a minefield and any enemy satellite coming near to one of these would be deep fried: by high voltage shock or low range emp or some other way!

Speaking my mind, I'm strongly against any form of war in space. The place is already so dangerous for humans, why fill it up with junk and bring petty human wars outside the planet?! Venturing into space is a necessary evil that must be done to make sure our survival in long run... SURVIVAL being the keyword!

nTripathi · Post by **nTripathi** » 10 Mar 2016 20:16

dhiraj wrote:OK congrats.. another PSLV success
However i am more interested to know about the shade which always comes in between the camera and the rocket clearing the launch pad and disrupt rocket's view.
How can DD repeat same mistake again and again in such a flawless ISRO journey in recent past

Hope, you are not being sarcastic here or trolling the potato quality of DD...

Explanation: it is not a shade but the camera's metering system that adjusts itself to the new source of light (combustion exhaust flames) in the frame...!

Varoon Shekhar · Post by **Varoon Shekhar** » 10 Mar 2016 20:55

Any idea what the current state of operationality of the IRNSS satellites is? Are people actually using them for GPS location and direction services? Is the government?

SaraLax · Post by **SaraLax** » 10 Mar 2016 20:56

manjgu wrote:saraLax...its not normal eyesight but narmal eyesight.... launch was narmal not normal.

Agree - I write abnarmaal post saar ! so Saary saar !!

member_28108 · Post by **member_28108** » 10 Mar 2016 22:03

IRNSS 1G is scheduled to be launched next month as per ISRO's Director

member_28108 · Post by **member_28108** » 10 Mar 2016 22:06

The vacuum tubes in IRNSS have a finite life so they will be switched on continuously after full deployment. I think they were transiently switched on for calibration etc (when the first 4 were launched) if my memory is right. They delay continuous operation though we can never be sure of the true status as any data will be first handed over to the military .
A lot of things done by ISRO never comes to public domain (a Chaiwalla to a chaiwall told me )

member_23370 · Post by **member_23370** » 10 Mar 2016 22:08

Wow didn't realize there was a launch. But its a boring old PSLV, wake me up when GSLV-III goes online.

Vipul · Post by **Vipul** » 10 Mar 2016 23:33

India to launch 25 foreign satellites from 7 countries this year.

India will launch 25 foreign satellites belonging to seven countries, with the USA topping the list in 2016 17, Rajya Sabha was informed today.

In written response to a question, Jitendra Singh, Minister of State in Prime Minister’s Office (PMO) which looks after the Department of Space, said till date 57 foreign satellites from 21 countries have been launched using the Polar Satellite Launch Vehicle (PSLV).

He said Antrix – the commercial arm of ISRO – has signed agreements with Algeria and Canada for launching three satellites each, four for Germany, one each for Japan and Malaysia and 12 for the USA in 2016-17.

In the last three years, from January 2013 till December 2015, ISRO launched 28 foreign satellites belonging to 13 countries, with Singapore, the United Kingdom and the USA topping the list.

ISRO earned 80 million euros for the launch.

vasu raya · Post by **vasu raya** » 11 Mar 2016 05:19

nTripathi wrote:
kit wrote:once the INRSS is in place would it be possible to block all GPS signals in India ? at times of war for example ?
well, GPS is operated by USA so in a situation of war they can selectively block the coverage of their positioning service in any region of the world and for any duration! However, I believe IRNSS can be used very efficiently to block GPS. The orbit of the Indian satellites is higher than that of GPS ones given that IRNSS can generate signals in similar frequency range as the GPS satellites. In a state of war, IRNSS satellites can use a fraction of their transponders to jam GPS signals an rest of the transponders to beam on strategic authorized users like the military...

(But I must say, in all cases if USA is not involved, jamming the GPS can create major international crisis.)

ok, back to earth, can the IRNSS aid in spoofing the GPS or BDS receivers starting with the LoC first, so that the targets the terrorists are aiming for are shifted and instead they are led to predetermined ambush points. The shift shouldn't be linear, so somebody crossing at any point on a specific section of the LoC is guided to a zone of x sq. meters where they can be monitored or intercepted. Use of military grade GPS units by them is ruled out unless some countries want to be named.

The distance between the border and the Pathankot airbase was less than 30 kms, the 'rumple on the digital GPS map' should be fine enough to fit within that distance.

Another aspect is not to use the IRNSS directly but to create a para system with nano sats for this. Lot of times people in remote villages report sightings of armed men with backpacks, but they seem to know their way back, so can GPS be spoofed at that micro level on demand?

nTripathi · Post by **nTripathi** » 11 Mar 2016 12:26

vasu raya wrote: ok, back to earth, can the IRNSS aid in spoofing the GPS or BDS receivers starting with the LoC first, so that the targets the terrorists are aiming for are shifted and instead they are led to predetermined ambush points. The shift shouldn't be linear, so somebody crossing at any point on a specific section of the LoC is guided to a zone of x sq. meters where they can be monitored or intercepted.

Jamming and spoofing of GPS using IRNSS satellites can be done only if you run only one transponder at a time with a highly focused beam to the target area (these are very high power consuming activities). This will probably negate GPS in that area but BDS will still be active since it operates in different frequency range. But there are some problems to this scenario:
1. Our own navigation system will become offline while spoofing command is active.
2. GPS started in 80s with L1 frequency for civilian use, newer satellites used L5 frequency but recently GPS is shifting towards M-band. So which one do you spoof with one transponder.
3. IRNSS itself is based on L5 and S-band frequencies, so can its transponders even produce L1 and M-band signals?
4. What happens to an aircraft that passes through the spoof zone. They use GPS. Can a chance be taken? Well, an experiment is required.
5. The incurred cost would be much higher than a ground based spoofing setup.

Another aspect is not to use the IRNSS directly but to create a para system with nano sats for this. Lot of times people in remote villages report sightings of armed men with backpacks, but they seem to know their way back, so can GPS be spoofed at that micro level on demand?

Nano sats wont work, they wont be able to generate required power. one answer could be launching a GEO satellite which 2 or 3 transponders and lots of solar panels: but it is probably a waste coz GPS bands would change over time. BDS may change. the targets might start using Glonass... Other answer is a chain of road vehicles that run along the border just for spoofing purposes. It too has problems of its own but is no doubt much better than the space setup!

SSridhar · Post by **SSridhar** » 11 Mar 2016 12:30

India to put 12 US satellites into space in 2016-17 using PSLV - ET

India will launch 25 foreign satellites in 2016-17 using the Polar Satellite Launch Vehicle (PSLV). While 12 of these belong to the US, the remaining 13 belong to six countries - Germany, Canada, Algeria, Japan, Indonesia and Malaysia.

Sharing these facts in response to a question in Rajya Sabha, minister of state Jitendra Singh on Thursday said, "The PSLV with its string of successful flights has emerged as one of the most reliable launch vehicles in the world. Till date, 57 foreign satellites from 21 countries have been successfully launched on-board PSLV, under the commercial arrangement between Antrix Corporation Limited and foreign clients."

Under the agreement signed between foreign clients and Antrix, the commercial arm of Indian Space Research Organisation ( ISRO), India will launch three satellites each of Algeria and Canada, four of Germany, one each of Indonesia, Malaysia and Japan and 12 of the Unied States in 2016-17.

In the last three years, from January 2013 till December 2015, the Indian Space Research Organisation launched 28 foreign satellites belonging to nine countries.

During this period, it launched seven satellites of Singapore, six of the United Kingdom, five of Canada, four of the US, two of Austria and one each of Denmark, France, Germany and Indonesia.

Singh said, "Antrix has earned revenue of 80.6 million euros through launch of these 28 international customer satellites."

kit · Post by **kit** » 11 Mar 2016 13:13

nileshjr wrote:Can we make an anti-sattelite weapon which will have surgical precision and would disable the satellite rather than blowing it apart. For example, a small robot thinggy going and attaching itself with the satellite and say fry its electronics, or damage its heat shield or damage its transponders or try and de-orbit it?? Something like that?? I know its quite challenging technologically, but we can do feasibility study at-least using nano/micro satellites.

the best way as the US does is to have "stealth" satellites which is almost invisible to space tracking systems .. these stealth satellites have counterparts in space mines that can be moved into place near an enemy satellite, disrupt it electronically or a hard kill

most details seem to be highly classified in the open domain

https://en.wikipedia.org/wiki/Misty_(satellite)

Dumal · Post by **Dumal** » 11 Mar 2016 13:46

http://www.wired.com/2016/03/russia-thi ... nd-rubles/

Russian thermal fission engines can take them to Mars and back but check out the other applications they talk about including cleaning up of space debris and other potential "not so innocent" applications.

You do not want to go to Mars. At least, not with today’s engines powering the trip. A chemically propelled voyage would take 18 months, one way. During which time any combination of boredom, radiation poisoning, and cancer will likely kill you. Suppose you make it? Congratulations on being the first Martian to die of old age, because a return trip from the Red Planet is currently impossible without using wishful logistics like fuel harvesting.

The Russians think they can do better. Last week, their national nuclear corporation Rosatom announced it is building a nuclear engine that will reach Mars in a month and a half—with fuel to burn for the trip home.

jamwal · Post by **jamwal** » 11 Mar 2016 14:49

Images from yesterday's launch of PSLV C32 carrying IRNSS 1F
http://imgur.com/a/yEMaE

member_29350 · Post by **member_29350** » 11 Mar 2016 15:41

Why aren't the water sound bafflers working? Isn't it done for all launches or only for GSLV type ones

member_28108 · Post by **member_28108** » 11 Mar 2016 16:29

They are there and flood as the blast goes through the lower channels through the blast deflectors laterally. If you see the video the water acoustic dampeners flooded the area at the appropriate time.

member_29350 · Post by **member_29350** » 11 Mar 2016 18:53

prasannasimha wrote:They are there and flood as the blast goes through the lower channels through the blast deflectors laterally. If you see the video the water acoustic dampeners flooded the area at the appropriate time.

Thanks for the clarification

member_28108 · Post by **member_28108** » 11 Mar 2016 20:13

You can see the steam due to the water acoustic damper

member_22733 · Post by **member_22733** » 11 Mar 2016 20:21

The accoustic damper is there to protect the launchpad for vibrational effects (and not to protect the environment), correct? Or am I wrong here?

Bade · Post by **Bade** » 11 Mar 2016 23:42

With regard to space junk...check out the nice long video on the topic in the link.

This one had self exploded in orbit last year...

http://www.space.com/29996-us-military- ... cause.html

"Analysis indicates one of the wiring harnesses lost functionality due to compression over a long period of time in the battery charge assembly," Air Force officials wrote in a statement today (July 20). "Once the harness was compromised, the exposed wires potentially caused a short in the battery power, leading to an overcharge situation with eventual rupture of the batteries."

http://www.space.com/20828-space-debris ... OKYrwu81mP

vasu raya · Post by **vasu raya** » 12 Mar 2016 03:07

nTripathi wrote: Jamming and spoofing of GPS using IRNSS satellites can be done only if you run only one transponder at a time with a highly focused beam to the target area (these are very high power consuming activities). This will probably negate GPS in that area but BDS will still be active since it operates in different frequency range. But there are some problems to this scenario:
1. Our own navigation system will become offline while spoofing command is active.
2. GPS started in 80s with L1 frequency for civilian use, newer satellites used L5 frequency but recently GPS is shifting towards M-band. So which one do you spoof with one transponder.
3. IRNSS itself is based on L5 and S-band frequencies, so can its transponders even produce L1 and M-band signals?
4. What happens to an aircraft that passes through the spoof zone. They use GPS. Can a chance be taken? Well, an experiment is required.
5. The incurred cost would be much higher than a ground based spoofing setup.

Nano sats wont work, they wont be able to generate required power. one answer could be launching a GEO satellite which 2 or 3 transponders and lots of solar panels: but it is probably a waste coz GPS bands would change over time. BDS may change. the targets might start using Glonass... Other answer is a chain of road vehicles that run along the border just for spoofing purposes. It too has problems of its own but is no doubt much better than the space setup!

1. yes, but then maybe it can be mitigated by using point beams, it gets better if other systems start to differentiate their frequencies
2. lets follow the trend of the receivers, they need to upgraded too to catch up with new frequencies
3. This is where we use transponders specific for the needs of jamming and spoofing outside the IRNSS
4. aircraft intersecting pencil beams or the dwell time in there should be very small to make an impact
5 and below: This is where small sats help, say ISRO provides the 'shell(s)' with all the housekeeping built in including power management (keeping the IRNSS sats as template), its the transponder and its frequency that are of consequence that can be integrated as competing systems evolve keeping the turn around time small.

This also provides transponders for generating point beams (point 1) by placing them in lower orbits and not divert IRNSS transponders themselves

The trouble with ground systems is there are too many places to cover within the country and this is just not limited to the hot zones and then the problem with managing as many people and resources.

The question was more about tech feasibility than seeking such answers in a public forum.

manjgu · Post by **manjgu** » 12 Mar 2016 10:43

pardon my ignorance of GPS etc..Q1) how does one get accurate lat/long coordinates of a spot/point on foreign/enemy soil ?? if a missile has to reach a spot/point using GPS then we must know its exact lat/long. Q2) how accurate in meters is the Indian GPS system once all the 7 satellites are in orbit? how does it compare with other GPS systems in operation today? Q3) does placing more satellites in orbit make it more accurate?

Shreeman · Post by **Shreeman** » 12 Mar 2016 11:09

1. trilateration, ask your friendly uncle guggal or auntie wikipidia. also remote sensing and irs.
2. normally if you are sending a sdre mijjile, then you wouldnt worry about.
3. Also trilateration, see 1.

manjgu · Post by **manjgu** » 12 Mar 2016 14:36

A) thanks Shreeman..i tried to understand but things are not clear. How do i calculate distances of a particular location which is in enemy territory to my orbiting satellites in absence of any emitters from that location?

as per reading the concept it seems 3 satellites can accurately fix locaiton of a place.but was wondering with how much accuracy?

member_28108 · Post by **member_28108** » 12 Mar 2016 14:41

^^^ The acoustic dampener is exactly that to prevent damage to the launch pad and prevent reverberations that can bounce back also on some of the launchers.

nTripathi · Post by **nTripathi** » 12 Mar 2016 18:17

manjgu wrote:pardon my ignorance of GPS etc..Q1) how does one get accurate lat/long coordinates of a spot/point on foreign/enemy soil ?? if a missile has to reach a spot/point using GPS then we must know its exact lat/long. Q2) how accurate in meters is the Indian GPS system once all the 7 satellites are in orbit? how does it compare with other GPS systems in operation today? Q3) does placing more satellites in orbit make it more accurate?

A1) there are a number of ways:
1. Direct triangulation from a phone or receiver requesting GPS data. (accuracy depends on number of sats at that time and number of times data has been requested)
2. Drone/spy sat imagery: Each image taken by these instruments has its own GPS data which is achieved through geometrical extrapolation of the known drone/spy satellite GPS+ground tracking data. (like 30 cm accurate)
3. Marking the target spot: Soldiers can leave infrared emitting lamps or an aircraft can illuminated the target with infrared spot which in turn can be picked by thermal imaging drone or sat to fix it GPS data. (pretty accurate as the last one)

A2)IRNSS guarantees 20m or better accuracy above the primary coverage area (larger than India). So once all 7 sats in orbit you may achieve 3-4m accuracy at best or 15-20m at worst. GPS is similar... in average best case scenario results have been 3.5-7.8m accuracy for GPS and 5-10m accuracy for Glonass. (sources: http://gis.stackexchange.com/questions/ ... acy-of-gps : http://beebom.com/2015/05/what-is-glona ... t-from-gps : https://www.quora.com/Which-one-is-better-IRNSS-or-GPS )

A3) Yes, but to a certain extent only if you are choosing to use one positioning service only. Multiple satellites can shorten triangulation time, strengthen signal to noise, mitigate error to the best possible scenario for that particular constellation. For GPS, these numbers are 3.351m of horizontal error, 4.684m vertical error (<95% statistical data) (source: http://www.nstb.tc.faa.gov/reports/PAN8 ... df#page=22 )

as per reading the concept it seems 3 satellites can accurately fix locaiton of a place.but was wondering with how much accuracy?

A) 3 sats required for a 2D fix, 4 sats required for a 3D fix of a target. The exact locations of all these sats in known through ground tracking. They have their atomic clocks synced to better than 20 nanosec accuracy (for IRNSS). the ranging of the target is done by measuring time difference between data request signals reaching the 4 satellites. these time difference are converted to distance differences by multiplying the light speed. Since the maximum error is contributed by the 20 ns clock differences (& since nanosec corresponds to mm when multiplied with light speed), we get accuracy results in centimetre values.. (for military and precision GPS equipments.)
(Note: Cant write about triangulation here, gonna take a lot of time. We can reach out through other means though!)

manjgu · Post by **manjgu** » 12 Mar 2016 19:33

nTripathi...say i want GPS coordinated of a building in pakistan or china..how will i put a reciever there or send a drone. I ofcourse dont understand how sat imagery can tell me GPS location..and if it does why do i need to put IRNSS in the air at all?? bit confused

Bade · Post by **Bade** » 12 Mar 2016 19:50

Why do you need IRNSS to get ground co-ordinates for anywhere on the globe. That accuracy is determined by your IRS satellites resolution if no other sources are available to you.

IRNSS is required by your post man to deliver the maal to the right address, as he needs to know where he is at any given time in the process of delivering maal.

member_22733 · Post by **member_22733** » 12 Mar 2016 19:54

Btw, gps, inrss etc is purely oneway communication, from sat to receiver. I think that will clear up some confusion.

manjgu · Post by **manjgu** » 12 Mar 2016 19:58

guys i am asking how will i get GPS coordinates of a point in enemy territory so that i can load GPS coordinates into my mijjiles !

Rahul M · Post by **Rahul M** » 12 Mar 2016 20:00

manjgu wrote:nTripathi...say i want GPS coordinated of a building in pakistan or china..how will i put a reciever there or send a drone. I ofcourse dont understand how sat imagery can tell me GPS location..and if it does why do i need to put IRNSS in the air at all?? bit confused

sat imagery == maps. no reason good accurate maps cant give you lat long of any location, as long as you can confirm from sat imagery that your target is where you think it is.

the IRNSS signals can then be used by the UAV/bombs/mizziles to guide them to that location.

guys i am asking how will i get GPS coordinates of a point in enemy territory so that i can load GPS coordinates into my mijjiles !

maps. really good military grade maps. if you can superimpose them on sat imagery then it's even better.

member_22733 · Post by **member_22733** » 12 Mar 2016 20:01

GPS coordinates are latitudes and longitudes. You look at the map, look at what angles it subtends wrt the poles and the gmt line, feed it into the mijjile and phire away.

manjgu · Post by **manjgu** » 12 Mar 2016 20:04

Bade..so u r saying its possible to get LAt/long of a point on the earth with IRS satellite? with our present IRS system what is accuracy of coordinates ..how many decimal places?