GPS DriftCast (GPS Drift 2.0) Vastly improved landing location prediction based on winds aloft forecasts

[JimJarvis50]

The wind forecasts are pretty good, so getting a nice parallel track should be pretty common. I achieved that in post #31. I am sure Jim is using the same speed and bearing approach as DriftCast.

The challenge seems to be getting the apogee location from the trajectory simulation. I'd like to see how Jim did that "with and without drift."

The approach that I use is just dirt-simple (or maybe brute force is a better term). From Windy, I take the predictions for 5 models and just average them, perhaps throwing out an outlier. From there, I just determine the wind speed for each thousand-foot altitude range during the flight, or perhaps larger intervals depending on the data. For the descent, I just take drogue and main rates of 80 and 25 ft/s to determine the time for each altitude range, and assume that the drift is equal to the wind speed. I'm normally starting with a pretty good estimate of the apogee position if it's a vertical flight. Getting the apogee position on the current flight was a little more challenging. The ascent, with and without drift, is important because the wind is the highest at the point where the rocket is slowing down. The process is the same, though, where the time spent in each altitude range on ascent is calculated from the simulation and then the windspeed is applied. The biggest problem is that Windy only gives 3-hour time increments and it is not obvious what time is associated with the data.

With the above approach on a 10K flight, I can typically get the apogee position within a few hundred feet and the landing position within perhaps 500 feet. That's good enough to avoid all obsticles except for the runways at Hearne.

Jim

 

[Buckeye]

The approach that I use is just dirt-simple (or maybe brute force is a better term). From Windy, I take the predictions for 5 models and just average them, perhaps throwing out an outlier. From there, I just determine the wind speed for each thousand-foot altitude range during the flight, or perhaps larger intervals depending on the data. For the descent, I just take drogue and main rates of 80 and 25 ft/s to determine the time for each altitude range, and assume that the drift is equal to the wind speed. I'm normally starting with a pretty good estimate of the apogee position if it's a vertical flight. Getting the apogee position on the current flight was a little more challenging. The ascent, with and without drift, is important because the wind is the highest at the point where the rocket is slowing down. The process is the same, though, where the time spent in each altitude range on ascent is calculated from the simulation and then the windspeed is applied. The biggest problem is that Windy only gives 3-hour time increments and it is not obvious what time is associated with the data.

With the above approach on a 10K flight, I can typically get the apogee position within a few hundred feet and the landing position within perhaps 500 feet. That's good enough to avoid all obsticles except for the runways at Hearne.

Jim

Thanks, Jim.

I am confused on your ascent analysis. Do you have wind in the apogee simulation? If so, there should be some weathercocking into the wind, right? However, it sounds like you are using the winds aloft to push the rocket with the wind. ????

For weathercocking into the wind, the sim results are very inconsistent. See this thread.

 

[kjhambrick]

I should let Jim explain how he shoots for an apogee position for his flights, but he was flying his VOS guidance system for his flight track.

This means that Jim's final apogee position over the ground wouldn't follow the normal vector sum of ( upwind ascent path ) + ( downwind drift ) + ( random YEET and YOINK ) that you and I and most other fliers have to try to calculate.

Jim's final apogee position over the ground will be a function of ( programmed VOS flight profile ) + ( downwind drift ) + ( random YEET and YOINK ) only.

-- kjh

 

[MarsLander]

Thanks, Jim.

I am confused on your ascent analysis. Do you have wind in the apogee simulation? If so, there should be some weathercocking into the wind, right? However, it sounds like you are using the winds aloft to push the rocket with the wind. ????

He is using his VOS. No weather cocking...lol

 

[JimJarvis50]

Thanks, Jim.

I am confused on your ascent analysis. Do you have wind in the apogee simulation? If so, there should be some weathercocking into the wind, right? However, it sounds like you are using the winds aloft to push the rocket with the wind. ????

For weathercocking into the wind, the sim results are very inconsistent. See this thread.

I have a vertical stabilization system on the rocket, so aside from an initial tilt and recovery when up to speed, I don't get weathercocking. Once vertical, however, the rocket will still drift with the wind on ascent. Actually, the rocket will drift with the wind even if not vertical.

Jim

 

[kjhambrick]

Dave --

I believe I've got HEDLEY LABAR ready for his maiden voyage ( ??? does a male rocket make a maiden voyage ??? )

HEDLEY is a 29mm BMS School Rocket I've been working on to learn Head End Deployment.

I've signed up for the Tripoli Houston Launch at Hearne, TX but my attendance is still a little up in the air because our granddaughters are coming home sometime Saturday and I am the designated picker-upper.

Anyhow, I decided to prepare for the launch, just in case.

Attached is the latest version 2.25 of GPS DC with the flight info for HEDLEY on an AT F67W Econojet Motor.

I also fixed the GPS coordinates of the Hearne, TX launch pad so it is in the proper spot instead of in the airport terminal

This is a screenshot of the Excel Program:


The Data was there under the [Saved Forecast] Tab this time !

This is a screenshot of googleearth with the landing scatter data:


Hmmm ... those landing spots are pretty close to the asphalt ... maybe I need to scoot my 2020 mini-button rail a little east

My fingers are X'd that I can actually make it to the launch but I'll let you know how it goes either way !

Thanks Dave.

-- kjh

 

[dvdsnyd]

Dave --

I believe I've got HEDLEY LABAR ready for his maiden voyage ( ??? does a male rocket make a maiden voyage ??? )

HEDLEY is a 29mm BMS School Rocket I've been working on to learn Head End Deployment.
.....

-- kjh

kjh -
Looks great! Hoping you get to fly as well.
We are supposed to have a launch on Sat, but we've gotten close to 3 inches of rain this week alone, and had gotten a bunch last week as well.
Fields/roads will be iffy.

One thing I would recommend is going to the latest 2.26 version of DC.
I fixed the forecast recall function so that it actually works in that version.

Thanks,
Dave

 

[kjhambrick]

Thanks Dave.

I downloaded and saved release 2.26 last week but I inadvertantly ran release 2.25 beta this morning ( ! DOOH ! )

Good luck with your weather and your site conditions this weekend and thanks again for the CLUE

-- kjh

 

[MarsLander]

Did forecast last night for LDRS and the Viper, about 1pm yesterday afternoon.

Included weathercocking based on Rocksim. Launched about 2pm, landed on the 2pm pin. Was maybe 2-400' due east of the 2pm simulation.

Close enough for me to use it again in the future. I did not have GPS onboard. Just going from the location of the trees. Certainly within the error of all the simulations, wind perturbations, rocket gyrations, yada yada yada.

 

[Buckeye]

Did forecast last night for LDRS and the Viper, about 1pm yesterday afternoon.

Included weathercocking based on Rocksim. Launched about 2pm, landed on the 2pm pin. Was maybe 2-400' due east of the 2pm simulation.

Close enough for me to use it again in the future. I did not have GPS onboard. Just going from the location of the trees. Certainly within the error of all the simulations, wind perturbations, rocket gyrations, yada yada yada.

View attachment 649259

Nice! What was the max altitude?

 

[MarsLander]

No altimeter...LOL.

 

[kjhambrick]

No altimeter...LOL.

Congrats again, @MarsLander !

What did RockSim estimate for Apogee ?

-- kjh

 

[MarsLander]

1932 or there abouts…

 

[dvdsnyd]

Did forecast last night for LDRS and the Viper, about 1pm yesterday afternoon.

Included weathercocking based on Rocksim. Launched about 2pm, landed on the 2pm pin. Was maybe 2-400' due east of the 2pm simulation.

Close enough for me to use it again in the future. I did not have GPS onboard. Just going from the location of the trees. Certainly within the error of all the simulations, wind perturbations, rocket gyrations, yada yada yada.

View attachment 649259

That's really Awesome!!
This was your L1 flight, correct?

 

[dvdsnyd]

The approach that I use is just dirt-simple (or maybe brute force is a better term). From Windy, I take the predictions for 5 models and just average them, perhaps throwing out an outlier. From there, I just determine the wind speed for each thousand-foot altitude range during the flight, or perhaps larger intervals depending on the data. For the descent, I just take drogue and main rates of 80 and 25 ft/s to determine the time for each altitude range, and assume that the drift is equal to the wind speed. I'm normally starting with a pretty good estimate of the apogee position if it's a vertical flight. Getting the apogee position on the current flight was a little more challenging. The ascent, with and without drift, is important because the wind is the highest at the point where the rocket is slowing down. The process is the same, though, where the time spent in each altitude range on ascent is calculated from the simulation and then the windspeed is applied. The biggest problem is that Windy only gives 3-hour time increments and it is not obvious what time is associated with the data.

With the above approach on a 10K flight, I can typically get the apogee position within a few hundred feet and the landing position within perhaps 500 feet. That's good enough to avoid all obsticles except for the runways at Hearne.

Jim

@JimJarvis50
I would be curious to see if you employed GPS DriftCast to your methods in one of your next flights. Look for version 2.26 at time of this writing.
Turn the weathercock table off, and set your launch latitude/longitude to your predicted apogee and run it.
I think the approach I am using for drift is probably pretty similar to you - mostly just brute force.
Only difference is the forecast. Within 45 hours of the launch, the forecast is RAP, which is one of the forecasts Windy uses.
Further out, Open-Meteo is used, which is similar to GFS I believe.

Thanks,
Dave

 

[Rocketclar]

Using 2.26 version and running sims to see how The Stinky Sewer Pipe Rocket will do on a J800 at the AMA site. Unfortunately, I may not have time to rerun sims tomorrow before the launch on Sat. Anyway, fingers-crossed, I'll see how we do and will report back.

 

[Rocketclar]

Well, everyone I showed DriftCast output today was impressed. And most of the rockets were drifting as the model suggested (unfortunately, into waist high corn). Several were in the range of my sim’s apogee ~2500-3500’ and they landed seemingly as predicted. However, while mine drifted close to a modeled line, it went further by about a 1000’. My sim was for 3561' but I got 3252'. I had tried to adjust the launch rail to 0 deg with a level. Unfortunately, our launch stands have some wiggle. Also, it seemed that the surface winds were more gusty and higher than the original predicted. And I probably didn’t use the best rocket for this….my Stinky Sewer Pipe rocket which is over 10’ tall with a fair bit of fin area, but on a J800. But I’m not discouraged because the flight lines were good. I didn’t get a GPS log as I had to change out to another Eggfinder unit and it didn’t have the data logger. I did get final GPS coordinates, just not the log, which has been funky anyway.

 

[dvdsnyd]

Well, everyone I showed DriftCast output today was impressed. And most of the rockets were drifting as the model suggested (unfortunately, into waist high corn). Several were in the range of my sim’s apogee ~2500-3500’ and they landed seemingly as predicted. However, while mine drifted close to a modeled line, it went further by about a 1000’. My sim was for 3561' but I got 3252'. I had tried to adjust the launch rail to 0 deg with a level. Unfortunately, our launch stands have some wiggle. Also, it seemed that the surface winds were more gusty and higher than the original predicted. And I probably didn’t use the best rocket for this….my Stinky Sewer Pipe rocket which is over 10’ tall with a fair bit of fin area, but on a J800. But I’m not discouraged because the flight lines were good. I didn’t get a GPS log as I had to change out to another Eggfinder unit and it didn’t have the data logger. I did get final GPS coordinates, just not the log, which has been funky anyway.

Thanks for the report!

Yea, like others, you've found the biggest limiting factor in the use of DriftCast...The up part and the GPS lat/long of apogee.
If that is close to your sim, I think DriftCast gets you close. If that's off, it gets tougher. But at least the general drift should still be the same.

We've gotten so much rain here lately, or launch got pushed out yet again. Still haven't been able to test my own program! HA!

Dave

 

[Rocketclar]

Here are the data.....I was able to run DriftCast about 24 hrs before launch. Seen is the Excel data sheet used along with the Google Earth Pro output, now planted in corn. A number of rockets from yesterday landed in the corn and along those lines. Stinky landed along the 12PM line, but about 1000' further at 40.17532, -85.31089, just across a road and into another corn field, and missing getting draped over a power line! It landed about 2320' away. My apogee was about 300' lower than predicted....normally, I've had closer agreement.

 

[kjhambrick]

There is an AARG launch tomorrow and I don't have Hedley ready to fly but T'Pring's P'Toy is ready to fly an H128W to about 3500 ft.

This is a screen shot of the GPS DC Screen for tomorrow's forecast:


And this is a googleearth overlay:


Looks like my best launch window is 11:00 to 13:00 CDT to miss the ponds and the bogs to the south and the tall corn field to the east, across CR 433

I'll report with actual info after the flight.

-- kjh

EDIT: p.s. I don't recall ever flying in TX when the winds were that low ! What a treat !!

 

[kjhambrick]

DOOH !

I scrubbed my flight because after prepping one of @Brainstormz123's Comspec Trackers for the flight at home, I left ALL my trackers at home on my desk.

The unharvested grass around the pads was 4-feet deep in some places and the corn around the Apache Pass airport was 4-to-5 feet tall.

Still had fun hanging around the LCO tent but ... DOOH !

Next launch window is with Tripoli Houston in Hearne TX on July 13 if Beryl does not make a mess over there and if the winds are favorable.

-- kjh

p.s. I ran another GPS DC the morning of the launch and the wind forecast had shifted a bit from the Friday forecast:


The hour-by hour predictions for the general directions were pretty good for the flights I watched until I had to leave at 14:00 CDT.

 

[dvdsnyd]

DOOH !

I scrubbed my flight because after prepping one of @Brainstormz123's Comspec Trackers for the flight at home, I left ALL my trackers at home on my desk.

The unharvested grass around the pads was 4-feet deep in some places and the corn around the Apache Pass airport was 4-to-5 feet tall.

Still had fun hanging around the LCO tent but ... DOOH !

Next launch window is with Tripoli Houston in Hearne TX on July 13 if Beryl does not make a mess over there and if the winds are favorable.

-- kjh

p.s. I ran another GPS DC the morning of the launch and the wind forecast had shifted a bit from the Friday forecast:
View attachment 655135

The hour-by hour predictions for the general directions were pretty good for the flights I watched until I had to leave at 14:00 CDT.

Thanks for the update!!

We will see if I get to fly on Saturday...the bigger question...will I be ready! HA

 

[kjhambrick]

Another month, another launch and another site ...

We ( AARG ) will be moving from Apache Pass to Hutto for the fall and winter months so below is T'Pring's P'Toy ( aka TP ) on the AT RMS 29/180 H128W that I didn't get to fly last month because I forgot my Comspec Trackers ( ! DOOH ! )

TP will reach about 3500 ft on the H128W and will be set up with a Blue Raven for main at apogee and drogue at 400 ft.

This is a screenshot of GPS Driftcast version 2.26 where I moved the pad about 200 yards south because of the anticipated condition of the newly plowed fields and some possible unmowed grass and some unharvested corn and sorghum in the fields north of the "Impenetrable Thicket" as it is unaffectionately known:



Note the last Hutto entry on row[ 30 ] where I 'moved' the pad about 200 yards south but left the waiver alone

This is the Google Earth screenshot of the GPS Driftcast Landing Scatter Plot:


I am glad Jim Jarvis is considering moving the pad south this month otherwise the Impenetrable Thicket might come into play for me and mine !

Thanks for GPS DC, Dave !

It is a lot of fun !!

-- kjh

p.s. I wanted to fly HEDLEY LaBAR on an F67 to 1100 ft but my granddaughters Ellie and Evie won't be there this weekend and they helped build him so they deserve to be there for his maiden voyage

Q: does a male rocket get to fly a maiden voyage ?

EDIT: I meant to ask about the Waiver Center and Waiver Radius Circle ... I can't make sense of it.

Should the Waiver Cylinder project on the ground as a circle with a 1-mile radius given my launch site info ?

When I measure the distances from the Waiver Center to the projected arc, I come up with about 1750 ft or so.

How do I interpret the Waiver info ?

Thanks again, @dvdsnyd !

 

[Rocketclar]

I can vouch for the thicket! When I launched there, I had a few recoveries in there and had to use the club's pole to pull a rocket or two down and out. One time I scared a herd of feral hogs out of there! Shorts and sandals won't work, you have to be covered up to minimize the thorns!

 

[kjhambrick]

As for the waiver radius number ...

Could the numbers in the .kml file be meters and not feet ?

When I measure the radius of the 1-nautical mile circle projected on the ground, I get 1750 -to- 1780 feet which is about a nautical mile in meters ( ? )

HTH !

-- kjh

Today's .kml file loaded into google earth:


p.s. Jim Jarvis gave me the actual (lat,lon) and radius for our Hutto waiver yesterday and I updated the AARG site info.

 

[dvdsnyd]

@kjhambrick
Yes, your interpretation of the waiver radius is correct.
The radius should project from the waiver lat/lon at the radius distance provided.
Somehow my conversion from nautical miles to km got goofed up.
See below, I have a waiver rad of 2 nautical miles, and it is now showing correctly using the measurement tools within Google Earth.
Updated version below in one of the later posts.
Thanks!
Dave

 

[kjhambrick]

Thanks Dave !

I'll be running a 'final' scan this evening and I'll merge my site info and my flight data and I'll use version 2.27

-- kjh

P.S. I couldn't wait ! Here is the Hutto Site run thru GPS DC version 2.27:



TLAR ! ( but I hope I never need that 1-nautical mile waiver cylinder )

 

[dvdsnyd]

Thanks Dave !

I'll be running a 'final' scan this evening and I'll merge my site info and my flight data and I'll use version 2.27

-- kjh

P.S. I couldn't wait ! Here is the Hutto Site run thru GPS DC version 2.27:

View attachment 659234

TLAR ! ( but I hope I never need that 1-nautical mile waiver cylinder )

What's funny(sad really) is I thought the waiver cylinder looked small when I was testing. Don't know why I never thought to test it.
Thanks for pointing out the bug, gave you credit

 

[kjhambrick]

What's funny(sad really) is I thought the waiver cylinder looked small when I was testing. Don't know why I never thought to test it.
Thanks for pointing out the bug, gave you credit

YW, Dave, but no ... THANK YOU

I never really did a reality check on the waiver cylinder for myself either.

I only looked at it this month because Jim said we might move the pad south this month.

As in all things in life, but especially in the art of contract science: THE BIG PRINT GIVETH, the small print taketh away ...

I reran my 2.27 sims this morning to check my drift against the latest wind forecasts.

I loaded the .kml landing scatter in google earth and I noticed for my H128W flight, that the waiver cylinder was only about 1770 ft.

So I selected the site and clicked [Get Elevation] and GPS DC reported an error.

I thought I might have borked the GPS coordinates of the waiver center so I tried the I211W flight.

Same error:


When I opened the debugger, this is the call stack ( right -to- left ), ( bottom -to- top ):


Is this helpful bug-hunting info ?

-- kjh

 

[dvdsnyd]

YW, Dave, but no ... THANK YOU

I never really did a reality check on the waiver cylinder for myself either.

I only looked at it this month because Jim said we might move the pad south this month.

As in all things in life, but especially in the art of contract science: THE BIG PRINT GIVETH, the small print taketh away ...

I reran my 2.27 sims this morning to check my drift against the latest wind forecasts.

I loaded the .kml landing scatter in google earth and I noticed for my H128W flight, that the waiver cylinder was only about 1770 ft.

So I selected the site and clicked [Get Elevation] and GPS DC reported an error.

I thought I might have borked the GPS coordinates of the waiver center so I tried the I211W flight.

Same error:
View attachment 659378

When I opened the debugger, this is the call stack ( right -to- left ), ( bottom -to- top ):
View attachment 659379

Is this helpful bug-hunting info ?

-- kjh

Weird,
Send me your spreadsheet that's giving you the error please.