TimWatson

I just received my little GPS data logger from Hobby King. Will log height,Speed.Distance and height. Just plugs into the receiver for power

going to try it in my boomer tomorrow

rcjetsaok

My Feedback: (7)

Tell us more... Link would be great !!!


Danno

fireblade5437

Link to GPS unit


http://www.hobbyking.com/hobbyking/s...ta_Logger.html

Alan

rcjetsaok

My Feedback: (7)

Very cool !!! Thanks.

Dan

TimWatson

Well I had a go with the little GPS Logger today and here are my results:

First flight I forgot to start the logging process. What a dolt

Second flight worked well. It was in a Boomerang Nano with a Wren 44 Gold

Flight Duration (Including taxi out and back) 8 Mins 45 Seconds

Distance Travelled 6.98 Miles

Max Speed (Groundspeed) 147.9 Miles/Hour

Average Speed (Includes Taxi) 47.9 Miles/Hour

Highest point in flight 1115Feet

This is a nice little unitand easy to work. All you do is plug it into a spare channel on the receiver for power. It will work on 4 - 12 Volts.

It only storesone flight and you read the data off the screen.For about £45I am pleased with it

highhorse

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I have used the same unit which I acquired under a different brand name and was sold elsewhere (can't stand HK and despise their lack of customer service)

It is indeed a nifty little toy which ends the mysteries and debates over how fast a model is. Took my P-160 powered Boomer XL to way high, made and extended 30 degree-ish dive, and recorded a max ground speed of 190. (Those of you who are cringing, fear not. My leading edges are taped and the pullout was very gentle!)

I need to do it again without any diving runs to see what the max level speed is.....guessing around 150-ish.

su27flanker

Mine just arived aswell its the same as the voltron unit sold else where it will be interesting to see the re****s

TimWatson

Did some more data logging last night in some foamies. Fastest we got was 117 miles/hour in a foam Habu. I must say the results I am getting seem faster than I would have expected so I am going todo a calibration test in my car in the next few days

Jgwright

It has been well established on this forum in other threads that using GPS is not an accurate way to measure speed because the number of data points is not enough when you have rapidly accelerating and turning model aircraft. You seem to be confirming it.

John

HarryC

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That's been my experience John. I carry a GPS with second by second logging, on every model jet flight and can review the flight ribbon on Google earth. Turns often have sharp angles like pentagons, the track will go places I can guarantee the model never went, and sometimes the speed says the model ran into a brick wall and then accelerated from near stationary to 150mph in a second. The GPS height is even worse, subject to considerable errors which seem mainly to do with it lagging far behind the model, so loops look like diamonds and according to the GPS the model lands about 15ft above the runway, then during the taxi back to the pits it slowly sinks down to the runway! If the model was a thermal-soaring glider then I suppose that the GPS lag would be able to keep up with the slow rate at which things change but it just doesn't seem to be able to keep up with the very rapid changes which jet models can make. Its data has to be taken with a pinch of salt
Harry

highhorse

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I was worried about that myself, until I realized that the results were consistent AND verified by a state trooper's radar gun..

HarryC

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I'm sure mine would pass that verification too, if it went in a straight line for long enough. It's our jet model's ability to change direction and height very rapidly coupled with the bank angles that send the GPS aerial into a poor orientation, that seems to bother the GPS unit which leads to some spurious readings.

I sometimes get a very high or low speed, or high or low height readings that are not impossible but are very unusual. By looking at the data for the second before and after I can see that one data point was clearly false. With the HK system that just records the one peak value you can be misled into believing that occasional false value. So if for example you regularly get a top speed of 80mph and suddenly one flight it says 100mph or 120mph, be very wary as it is probably a false value.

alasdair

As Harry says, if all you get is a reading of the maximum speed and height recorded in a flight, the unit is worthless and the data meaningless as it only takes one single false data point to screw up the results completely.
Remember how these things work. They measure a 3 dimensional position (they don't measure speed) at a fixed time interval between each. Then they calculate the straight line distancebetween each pair of positions, divide by the time interval to calculate the average speed in that segment. Position accuracy on GPS is what? Plus or minus 5 metres? maybe 10 metres? If the time interval is short and two adjacentpositions are 5 metres out in opposite directions then the distance is 10 metres too much and the speed greatly exaggerated. And that is assuming that every single position was calculated using good GPS data.

I have used GPS recorders twice.

I attached a GPS unit to my Eagletree data recorder. I found that it did not lock on to satellites very reliably, and lost signal if the model banked significantly in turns. The data was useful only on takeoff andin subsequentlong straight runs if no aerobatics were included.

I also had GPS in a Weatronic Rx (on 35 MHz) with twin aerials. It recorded GPS position continuously and recorded it on an SD card. Also recorded was GPS height and calculated speed. The card could be downloaded into a computer. Satellite lock was more reliable (because of the twin aerials I guess) and the data was almost continuous.

When data is continuous and can be viewed on a graph,any spikes caused by bad data or positioninaccuracycan be disregarded, by smoothing out the graph to take away the spikes. It can then be very useful as a cross-check of air pressure based data, and I found the ground track information useful too. On its own, the GPS data from Weatronic was good, if allowance is made for the wind.

Continuous GPS data logging can be useful, but from what has been said about this HKrecording device, I surmise that all it shows you is the biggest spike!!!

highhorse

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Seriously guys? You think the average jet user is stupid enough to be "misled by an occasional false value" and that said occasional false value makes the unit "worthless"? You don't think we all understand that spurious data exists in the world or that we can cope accordingly?

Believe me, gentlemen, you are selling your peers short.

indubitably

My Feedback: (14)

Why does it have to be accurate? Where are we going? Its all about vicarious stuff, and a relative number is fun if we think its accurate enough. WE just have to think its accurate, why take that away from us? Lets have fun and fantasy.

HarryC

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Then why spend money on it, just make up a number

HarryC

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I don't know about the "average", but some are

TimWatson

Well I will give you a clue shall I it is called fun. Bean counting and worrying that it is not accurate is boreing, worrying about your money and how you spend that is even more borinng.I took it to our club fly in last night and several of us had a real laugh with it comparing readings in various planes and 2 Habus trying to beat the others numbers. I paid £45 quidfor it which is less than the price of a night out. I have already had my moneys worth.

By the way I did a test today against another GPS device which has been calibrated and the 2 were within 2 % which is fine with me.

Live a little and enjoy life

alasdair

Suckers!!!!

I've just been watching "Big Bang.." and realised in my last post I'm beginning to sound like Sheldon.

So go and have your fun, and play quietly.

drdoom

My Feedback: (9)

Ive had fun with mine. I was surprised to see just how fast the 2 jets I used mine in were. The formost with P-70 max speed was 124 MPH and My Falcon 25 with P-20 maxed out level at 139 MPH.
Most of my flights averaged 5 to 6 miles. and didn't go over 250 f above the ground.

I love the fact it remembers the last data even if power is removed, and it is Backlight Blue.

highhorse

My Feedback: (2)

I would like to echo a post above. It's about the "fun factor". If my jet's data spiked at something unreasonable, I would know that and ignore that data. But the giggles from the data I and friends have gotten so far, in everything from electrics to jets, is well worth the price.

su27flanker

been testing mine if you fly straight simple passes it works well, but really tight turns and acro is a no no if you want a clear reading

JoeEagle

My Feedback: (26)

have you tried the Eagle Tree GPS V4? 10hZ rate. plots directly to GE. tells you how many satillites you have (i usually have 8, sometimes 10) HDOP, course/heading, distance from start. its pretty cool to look at the plots on GE as it show you where you are flying over your club field. it shows me taxing out and takikng off slightly off the centerline.

here is a .kml file i had to rename it .jpg to get it to upload-just rename the file extension to .kml and if you have GE on your machine just click on it and have a look.


more $$ than HK but Bill is a great guy to work with-and his service department is also great.