Date
1 - 6 of 6
HAB predictions
|
Sasha Tim
Hey all, In general, how do the predictions of the CUSF engine (predict.sondehub.org) compare with the actual landing site? I've heard the figure of +- 2 miles. What is your opinion on this? Still working out a few RTTY transmission bugs with my payload, then hopefully launch this week! Code is here https://github.com/radio-satellites/lab-ses-hab/blob/main/cubesat/main.cpp. If anybody could help figure out why the longitude doesn't always transfer correctly (occasionally, it just skips a digit in the decoder, although the datastring[] is always fine) it'd be wonderful!!!!. 73! Sasha VE3SVF |
|
|
|
Bruce Coates
Hi Sasha I'd be cautious about relying on any predictions being that accurate every time. There are simply too many variables at play. When the weather conditions are fairly stable, the sondehub predictions can indeed be within a few miles. On the other hand, if the weather is variable, it introduces a much higher degree of variability that will impact the accuracy of any prediction. Add to that the fact that your actual flight ascent/descent/burst may differ from what you entered which will impact the prediction. I think another factor for me is that the wind data sources are several hundred km away from Saskatoon in all directions so my wind data is already a predicted value and thus less accurate. I short, the sondehub predictions are amazingly accurate but a lot can change between the prediction and the your final touchdown. Our general procedure is to travel to near the predicted burst, the exact location depends on where we can buy drinks and snacks (grin). We then watch the actual flight compared to the predicted flight and adjust the new landing prediction if they differ. 73, Bruce - VE5BNC On Wed, Mar 15, 2023, 5:06 p.m. Sasha Tim <sasha.nyc09@...> wrote:
|
|
|
|
Dennis Klipa - N8ERF
Sasha, I am sure results vary, and depend a lot on the accuracy of the input and how recent the winds aloft data is. Getting the "neck lift" accurate under windy conditions can add a significant error. My experience over only 12 launches is +/- 10% of the total distance traveled. So, IMHO, the observed error in the prediction is not with the code but with the parametric input. Happy flight! Best Regards, Dennis, N8ERF On Wed, Mar 15, 2023, 7:06 PM Sasha Tim <sasha.nyc09@...> wrote:
|
|
|
|
Jerry
I did a comparison of 3 different predictors a few years ago for GPSL and all 3 predictictions were very close to the same. I also took the flights from the previous a year's GPSL and when I used the actual burst altitude, ascent and descent rates the flights were quite accurate based on the wind available at launch time. The problem is it is very difficult to get those 3 variables correct.
toggle quoted message
Show quoted text
There are several chase programs that update the actual as the fllight progresses. One of the easiest numbers to get close is the descent rate so if you run a prediction soon after burst you should get close to an accurate landing site.
|
|
|
|
In my experience the error is greatest in the direction of travel - less so at right angles to it. I suspect the predictor is quite accurate - its the other factors that cause most of the error. Steve G8KHW / AJ4XE
On 15/03/2023 23:49, Dennis Klipa -
N8ERF wrote:
|
|
|
|
Mark Jessop
As others have said, the predictor accuracy is often mainly limited by the user inputs (e.g. ascent rate, burst altitude and sea-level descent rate), and how closely your flight actually achieves these. In particular, your burst altitude is going to play a big part in this. If you are not using a well-characterised balloon, then calculators like sondehub.org/calc/ will not be good at estimating this. As for your RTTY code, I suggest digging into code from a known-good tracker like this: https://github.com/RoelKroes/TBTracker/blob/master/Misc.ino#L35 This also has code to add a CRC16 to the end, which is pretty important with a mode without error correction like RTTY... 73 Mark VK5QI On Thu, Mar 16, 2023 at 7:59 PM Steve G8KHW / AJ4XE <steve@...> wrote:
|
|
|
