Telemetry and data transmision Q
 

I am bidding on some jobs and I know that there has to be a Pelican with this field of expertise....

Let's say I am going to be flying geological surveying missions and want to transmit the onboard camera data back to a ground based receiver. To me, this sounds no more complicated than what the news choppers do.

What I would like to know is

(a) is that transmission somehow encrypted to prevent intercept by unintended persons?

(b) what is the range capability? The contract I am bidding on specifies a MINIMUM of 200 miles transmit capability. That seems like a big power requirement to me.

Airplane will be a Cessna 208B, so there is a capability of hauling a large amount of equipment.

What are some recommended sites and resources for me to check out?

Sounds like a cool gig!

I would ding Seahawk if he doesn't chime in soon.

Cash,

So much to consider. I am writing a proposal right now for UAS surveying in the Philippines.

There are a ton of data links, etc. available but you need to be sure of the frequency allocation in the area you are bidding on...it varies greatly from country to country. Some links use a part of the spectrum that can be an issue.

200 miles is a hump because all the links in the class you are discussing are line of sight. Depending on terrain, a two hundred mile slant range could be difficult. I am assuming sat links are too expensive? Is 100% connectivity require? That is going to drive cost.

Encryption is extra but not hard.

Some things to look for are compression algorithms that can increase down link speed, etc.

Also look for EMI issues on the aircraft and antenna placement...to me that is going to be your biggest problem, especially given the range requirements.

If you want to chat you have my number.

Best.

Thanks Paul.
I'm overseas right now, but hopefully will have more info from the client when I return to the States in a week or so.

Paul... 200 miles between ground points would be a challenge on almost any terrain.
I think 200 miles between an airborne transmitter and a ground base should be doable with enough wattage.

I also like the idea of a sat link, but not sure the client has even considered that. Heck, Iridium may have a COTS solution.

Call me when you get back.

I made a few calls (ok, I was practicing "proposal avoidance") and this one needs to be thought through...lots of integration issues.

Nothing you can't handle, but it needs to be factored into your bid/no bid.

Enjoy the Kitty Litter, spent a few years of my life wandering the Middle East.

And thanks, Sydney...

Geologic surveys eh?

Need a geologist? Will work for scotch and flannel.

Geologic surveys eh?

Need a geologist? Will work for scotch and flannel.

A few questions;

Do you have to transmit, local storage and unload after is a better solution
If you have to you will probably need a licensed spectrum for transmission depending on where you are flying, height, regulations - several commercial radio technologies available in this space.

How high will you be flying and how much data will you be capturing and transmitting?

Bob... At this point my information is pretty limited. All I have is an email from my POC asking if we are interested in providing such capabilities. I have started some back-and-forth dialogue with them now and should be receiving more details in the next few days.

What I know so far is that they expect the data to be received from the airplane by a ground station, and stored in a server with no less than 7tb capacity. I do not know if there will be two way data traffic to the airplane, and do not know if the received data will be re-transmitted or offloaded and trucked to a central analysis center.

I'll post more as it is made available to me.

What did we call those as kids..... "control line" planes?
It's gonna be one hell of a big circle.

It is strange that they want telemetry.

Is the project in the USA?

The cost to transmit the data is going to me a lot. Why not wait for the end of the day flying and have it all in one chunk?

We do aerial photography and mapping for a living but we just fly two hours after sunup and two hours before sundown. Except for thermal projects. Then we fly day and night for a comparison.

seems like a better idea.

But if you're stuck on a live feed, how about something like this: High Speed Satellite Internet While In Motion

says you can get 495kbps
http://www.groundcontrol.com/images/...0_Banner13.jpg

He will likely need several Mega bytes per second to keep up with aerial mapping data. We can suck up 500 gig of storage and up in one day of flying.

It would be interesting to see the specs on what the client needs or wants.

Yeah... I'm still waiting to see what their exact specs are.

Most of the crazy complex RFPs we see are issued only to satisfy the rules of bidding. They are written to fit one companies services exactly. Only one company will have the exact equipment needed to fit the bid. The RFP is usually written by the company that will win the bid and just handed to the customer to put out there for other companies to waste their time chasing.

Unless you need your data on the ground immediately, store it on the aircraft. Eliminates encryption, antenna, etc...and you still need the same amount of storage on the ground.

70Satman knows telemetry.

I understand, and have seen this also. It *may* be the case, however I think it is highly likely that the customer (a) does not understand what they are asking for, and (b) does not know what they really need. In other words, probably just a group of guys saying "This sounds cool. Oh yeah, and let's add this... And mud flaps also!"

Fint.... I doubt they *need* it.

Oh we see that a lot as well.

One RFP came from a city that wanted just stupid complex expensive things. The RFP was over 100 pages. We just trash the thing and did not submit a bid. They did not receive but one reply and it was for HUGE bucks. The budget was not there and they decided to get reasonable.

I suspect when your client sees what the telemetry alone costs they may decide on-board data storage is fine.

From what I have heard the F1 teams stream telemetry from the car back to the home office and they hav up to a TB of data per team. I presume they stream if from the car to the track side receiver and then somehow get it back home. I wonder what they use?

Dude, if ground station has 7TB server, it kinda means they expect rather high data rate. While hi-speed microwave data links can be arranged in stationary fashion, doing so for moving target while keeping high bandwidth and reasonable BER (bit error rate) gets *really* expensive. As your transmission protocol would need to cater for dropouts, multipath/doppler errors etc. you end up with needing double the bandwidth as half of data being sent would be error correction, parity etc.

So unless you are transferring less than 500kB/sec or have a budget of a small county, I recommend packning a 4-bay NAS + power converter on a plane. 10TB can be nowadays kept in a small 4-bay NAS, running four 4TB discs in RAID-5 and happily swallowing 100MB/sec while using 100W of power.

Thus, unless they are doing something really funky on ground and need real-time telemetry there is no point transmitting data. You could theoretically fly 1PB worth of storage even on a Cessna.

COTS, 8TB:
ReadyNAS Business Desktop Storage - RN31442E | ReadyNAS | Storage | Business | NETGEAR

P.S. This is basically "office" stuff and needs to stay pressurized and reasonably vibration free. If you plan to keep it unpressurized and/or exposed to vibration you need a Flash array storage. It means 10X the cost (but will still be doable, compared to hi speed 200 mile data link which is rather unpractical in my book)

Yup. I was going to share that with Cash but I like your style.:D

Yep, all of our data storage hard drives used in the airplane are solid state. A spinning drive quits at a surprisingly low altitude.

beepBeep and others - I am appreciating all of this input.

Glen... This client is one that I am working with on some other projects, so I really don't want to just dismiss their request. What I prefer to do is to work with them and guide them toward a better solution, and I feel you guys are certainly giving me some good feedback with which to move forward with this client.

There is another aspect of this project that it sounds like you guys would have input on, and this is a (hopefully) more realistic endeavor.

Could you deploy a truck or van sized vehicle (like a U4000) as a relay station? The idea is to create a chain from the aviation downlink, across areas with zero infrastructure, back to a city or to a permanent ground station. Or is there any reason a mobile station would need to be as large as a semi trailer with a containerized office. My concerns are power requirements (generators) equipment footprint, and need for air conditioning for both personnel and equipment. Would a 50 mile range be realistic for a mobile unit? 100 miles?



I'm sorry that I cannot post every bit of the information that I do have on this Geological Survey project but I have signed a confidentiality agreement with the client, and some of the stuff I have should not be posted due to those sensitivities.


As a related side story, once upon a time when I was in the Army, we flew "mapping" and "training" missions. Strangely (or not so much) every one of our missions were parallel to a another countries border, and all of our sensors and cameras were aimed at the border. (We must have needed a LOT of maps of that area.)

At that time, all of our data was recorded on mag tape, and all of our video and photos were on film. We could drop film canisters to waiting ground units, but other than for training purposes, we never did that. We would just hold them until we landed and the ground crew would retrieve them from the plane. In practice, the only time we would have made a canister drop was if we were going to be flying back and forth into an area where we may have been shot down. The drop was to assure that critical data was not lost with the plane.

I hope this helps clarify a few things.

Data security is really not a issue, even if you carry storage on board, as most NAS/SAN storage racks offer strong on-the-fly data encryption. So even if plane crashes, nobody would be able to restore the data without correct key.

But if you really insist on data link through radio, your best bet is probably ad-hoc LTE (=4G) network. It's made with moving radio datagram transmission in mind and has all the stuff to cope with it. (But due to time+frequency division multiplex scheme, I believe there is a hard limit of 100 km regardless of signal power due to timing issues.)

Basically, you would need a portable LTE cellphone station(s) for each cell within 100km of the plane. Such stations usually need fibre backhaul in-between but I suppose something could be cobbled together with microwave links.

Never underestimate the bandwidth of a Cessna full of RAID enclosures ....

Haha...I was just to post the same thing. NEver underestimate the bandwidth of 40-ton semi filled with LTO-6 tapes :D

With our 9x9 film camera we can fly 600 pictures at high altitude or many thousands at low altitude before we have to land for fuel. Each frame of film is 1.1 gig when scanned. The digital camera has a 2 TB solid state RAID. That will outlast the fuel as well unless it is low altitude.

The logistics is totally different. During a big mapping project we can just keep adding another roll of film no problem. With digital after a day of shooting it takes a while to copy all the data off and you have to do that twice for redundancy. Then erase the data cartridge before the next flight or get a different very expensive data cartridge.

Try to copy one TB of data with error checking from one drive system to another. It just takes a while. You have to do it twice to have a redundant copy in case of a bad hard drive or copy error.