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# Spotting calculator

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I have an idea and need some genius (or other capable person) to help make it happen. I think it would be a handy thing. Here's the idea.

I lot of areas of the country have winds at very different directions and speeds at different altitudes at certain times of the year. Here in southeast Texas for example, in the winter we can have ground winds from the south at 5, while the uppers at 13k are screaming 70 from the west or northwest. Complicating matters, the wind will actually change direction slowly as the altitude changes, creating a constantly changing drift direction.

I want to have a simple way to calculate where the "perfect" spot is by using something like excel or other common application. I want to input the wind speed and direction at the commonly reported altitudes (as reported by flight service, or observed by the pilot on previous loads using GPS) like 3k, 6k, 9k, 12k, along with the exit and deployment altitudes and the type of jump (think different speeds equals different freefall times equals different amounts of drift) and have it tell me where the spot is - measured in distance from a target like the peas or center of the landing area. Kind of a high-tech way to throw a WDI, but includes freefall in the calculation. The spreadsheet figures out the cumulative drift distance and direction, then reverses that to display the distance and direction needed to exit from any given point.

It would work for any group from headdowners to wingsuiters, and for any target location.

Any takers?
Chuck Akers
D-10855
Houston, TX

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I've been thinking about doing something like that for a while, just haven't had the time or motivation. I'll bet Kallend could modify his separation program to do what you want quite easily.

- Dan G

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That would be pretty nice, then you do an overlay of a map / photo of the drop zone with GPS coordinates...

If I had my IT guys do it, it would be approx \$1.2 million and take 7 months. Or some smart kid with excel will figure it out tomorrow. I will give it some thought and let you know what I can come up with.
Fortunately, I'm adhering to a pretty strict, uh, drug, uh, regimen to keep my mind, you know, uh, limber.
--- The Dude ---

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What you described already exists, the military has been using it for ages via the stubby pencil method but we also have an excel sheet that does the same thing. However, there are a few things that make this a bit more difficult than you think.

Before I list a few points to consider, I suggest you do a search on "do bad spots really exist". Before there was a file size limitation back then, I posted a few power point presentations that will show you how to do this and also explain things like doglegs and incompatible winds that make using an excel sheet, when either of these two things is present, un-doable.

Also, if you own a Garmin eTrex GPS, there was a jumpmaster feature on it that basically does this, but it is time consuming to use and it uses the military way of determining a spot which is not always desirable or feasible with skydiving operations.

1. As I eluded to above, using this method, be it stubby pencil or excel sheet, you are going to find that the resulting spot (depending on the winds) is a good deal away from the DZ. Most skydiving DZs have a general "pattern" that they fly dependent on the winds that is usually over or close to the DZ. Using distance and direction calculations for determining the spot is always going to put your spot outside of what most consider a "normal" jump run. When I say this, I mean that in some cases if I opened the door and told civilian skydivers to get out on the calculated spot , they would think I was insane and that they would never make it back. This is the biggest reason why this method will not work for civilian skydiving operations, not to mention that it requires updating as the day goes on and is far less forgiving than the way skydiving operations currently operate.

2. Doglegs and incompatible winds. I won't try to explain it here as it would take to long,besides the PPT show explains it in detail and how to compensate for it via the stubby pencil method. With an excel sheet, this is an issue as it will spit out an incorrect set of numbers (trash in, trash out). Also, if using wind directions from 315 degrees to 045 degrees to calculate average wind direction, erroneous averages may result on an excel sheet. To compensate, you must add 360 degrees to directions of 001 to 045 degrees before you plug those numbers into the excel sheet. You also will need to figure for magnetic to true for wind direction and drift as you have to transfer this info to a map to plot it. You also have to figure in for forward throw.

3. This method is not easy to implement and most people can't or won't(or don't have the skills/resources) do it as it takes a good deal of effort beyond what is done in civilian operations, even with the excel sheet.

4. Part of the formula requires that you know the "K" factor for the canopies being used. In skydiving operations canopies vary drastically in some instances. This "K" factor can be adjusted for but it further complicates and increases the likely hood of some people landing off a lot more than what we see now in civilian operations. Again, none of this is taking into consideration the other factors such as exit separation and exit order, which would further make this unfeasible since most people can't even exit the aircraft when the green light comes on without waiting for a few seconds or longer.

I could keep going on but I think that those who are interested will look at the PPT presentation and then see why this really isn't a good idea for civilian skydiving operations.

EDIT to add: This method also requires that the jumpmaster know how to really spot. Not a typical skydiver spot, but actually have the A/C door/ramp open and visually look for a geographical reference point on the ground, identify it correctly and then release the jumpers when over it, not before, not after. Real spotting using this method is an art and requires more than what is called "spotting" in skydiving circles.
"It's just skydiving..additional drama is not required"
Some people dream about flying, I live my dream
SKYMONKEY PUBLISHING

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This is already done to an extent by MFF Jumpmasters and AF Navigators using a modified version of D=KAV.

D=Distance, in meters
K=Constant
A=Altitude, in feet, reduced to one digit (i.e. 8000=8)
V=Velocity, in knots

They use the formula twice, once for freefall drift (canopy opening altitude up to exit) and the second for canopy drift (openning altitude to ground).

They also break the direction down for Freefall and Canopy drift as well. They average the direction and come up with a mathematically correct spot once the two portions are plotted out.

It is a good start for the wind dummies, but load one (or the WDI's) will show that load 2 should mnake some minor corrections. For the SOF guys if it is the only load, well good luck.

Matt
An Instructors first concern is student safety.
So, start being safe, first!!!

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I bow to you, you type faster. You also put more info in your post.

Matt

An Instructors first concern is student safety.
So, start being safe, first!!!

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Another problem is that the winds aloft forecast is just that, a forecast. It is calculated at various altitudes and is not always accurate.

Plus, many drop zones have a small number of preferred jump run directions regardless of winds, perhaps because of landmarks, multi-airplane tracks, or avoidance of congested or unhealthy landing areas. Sometimes a DZ will even eliminate a full section of the compass from consideration for exits.

In the civilian world we are always jumping over the same known location, so it makes more sense to identify the forecasted winds, build a paper and pencil spot, and compare actual aircraft track with the proposed jumprun. Then real live humans can make the needed corrections based on all the things computers don't quite grasp.
Tom Buchanan
Instructor Emeritus
Comm Pilot MSEL,G
Author: JUMP! Skydiving Made Fun and Easy

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The Garmin 60CSx handheld has the "jumpmaster" feature too.
It's pretty unwieldy, at least for civilain use.

Especially since wind aloft forecasts are pretty far apart, only for 3,6,9 and 12 thousand feet (and higher, but that's not important here). The closest one to my DZ is 25 miles away.
"There are NO situations which do not call for a French Maid outfit." Lucky McSwervy

"~ya don't GET old by being weak & stupid!" - Airtwardo

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Quote

What you described already exists, the military has been using it for ages via the stubby pencil method but we also have an excel sheet that does the same thing. However, there are a few things that make this a bit more difficult than you think.

Before I list a few points to consider, I suggest you do a search on "do bad spots really exist". Before there was a file size limitation back then, I posted a few power point presentations that will show you how to do this and also explain things like doglegs and incompatible winds that make using an excel sheet, when either of these two things is present, un-doable.

Also, if you own a Garmin eTrex GPS, there was a jumpmaster feature on it that basically does this, but it is time consuming to use and it uses the military way of determining a spot which is not always desirable or feasible with skydiving operations.

1. As I eluded to above, using this method, be it stubby pencil or excel sheet, you are going to find that the resulting spot (depending on the winds) is a good deal away from the DZ. Most skydiving DZs have a general "pattern" that they fly dependent on the winds that is usually over or close to the DZ. Using distance and direction calculations for determining the spot is always going to put your spot outside of what most consider a "normal" jump run. When I say this, I mean that in some cases if I opened the door and told civilian skydivers to get out on the calculated spot , they would think I was insane and that they would never make it back. This is the biggest reason why this method will not work for civilian skydiving operations, not to mention that it requires updating as the day goes on and is far less forgiving than the way skydiving operations currently operate.

2. Doglegs and incompatible winds. I won't try to explain it here as it would take to long,besides the PPT show explains it in detail and how to compensate for it via the stubby pencil method. With an excel sheet, this is an issue as it will spit out an incorrect set of numbers (trash in, trash out). Also, if using wind directions from 315 degrees to 045 degrees to calculate average wind direction, erroneous averages may result on an excel sheet. To compensate, you must add 360 degrees to directions of 001 to 045 degrees before you plug those numbers into the excel sheet. You also will need to figure for magnetic to true for wind direction and drift as you have to transfer this info to a map to plot it. You also have to figure in for forward throw.

3. This method is not easy to implement and most people can't or won't(or don't have the skills/resources) do it as it takes a good deal of effort beyond what is done in civilian operations, even with the excel sheet.

4. Part of the formula requires that you know the "K" factor for the canopies being used. In skydiving operations canopies vary drastically in some instances. This "K" factor can be adjusted for but it further complicates and increases the likely hood of some people landing off a lot more than what we see now in civilian operations. Again, none of this is taking into consideration the other factors such as exit separation and exit order, which would further make this unfeasible since most people can't even exit the aircraft when the green light comes on without waiting for a few seconds or longer.

I could keep going on but I think that those who are interested will look at the PPT presentation and then see why this really isn't a good idea for civilian skydiving operations.

EDIT to add: This method also requires that the jumpmaster know how to really spot. Not a typical skydiver spot, but actually have the A/C door/ramp open and visually look for a geographical reference point on the ground, identify it correctly and then release the jumpers when over it, not before, not after. Real spotting using this method is an art and requires more than what is called "spotting" in skydiving circles.

I think I'll stick to throwing out a weighted sheet of yellow crepe paper and watching it drift to the ground.

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Norden bombsight

"Meat bombs are over target, sir."

I always wait for the first Skyvan load to exit.
The pilots then adjust the spot and we are, (hopefully) closer on load 2.

Instead of all the technology, I just have a cup
of coffee and watch.

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If you design and construct an idiot-proof spotting calculator then someone will just invent a better idiot.

I doubt the consistency of even a well designed spotting calculator would improve upon that of an experienced spotter.

-Michael

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Quote

If you design and construct an idiot-proof spotting calculator then someone will just invent a better idiot.

I doubt the consistency of even a well designed spotting calculator would improve upon that of an experienced spotter.

-Michael

- airplane speed.
- wind direction and speed measured at 2K feet intervals.
- rotation of the Earth.

All those factors are of value once the jumpers are
in freefall. However, it doesn't take into account the
drift based on drag created by:
- jumper suit fabric.
- jumper weight.
- formation size.
- formation fall rate.

Once you know all the freefall variables, it is climbout.
- when the group climbs out.
- how long will it take (size of group).
- how long will the count be.

Rube Goldberg machines
Quote

The "Self-Operating Napkin" is activated when the soup spoon
(A) is raised to mouth, pulling string (B)
and thereby jerking ladle (C)
which throws cracker (D) past parrot (E).
Parrot jumps after cracker and perch (F) tilts, upsetting seeds (G) into pail (H).
Extra weight in pail pulls cord (I), which opens and lights automatic cigar lighter (J), setting off skyrocket (K) which causes sickle (L) to cut string (M) and allow pendulum with attached napkin to swing back and forth, thereby wiping chin.

After-dinner entertainment can be supplied with the simple substitution of a harmonica for the napkin.

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While I think it is useful to point out all the various factors that go into some sort of mathematically perfect spot, in practice I don't think things need to be that complex.

The numbers spit out by a calculation could still be compared to normal practice in typical conditions, to help figure out what to do in atypical conditions.

Let's say a common condition at the DZ is 10 mph ground wind from the west, rising to 30 at altitude. If the computer spits out a spot .9 nm west, but everyone knows that on a day like that the green light is turned on at .4 nm west, then one already has a guide about what degree the computer number should be varied for "real life" use.

Admittedly one gives up some accuracy if one can't figure out how to simulate every aspect of the real process, but the idea is to help get a better spot, not a perfect one.

Then when the computer helps calculate a spot for a day with weird winds and doglegs, one can make an adjustment given one's experience of the computer number vs. the real life number.

It's hard to tell whether the idea of a little spreadsheet will get shot down because "it's too complex", or "it's not really that complex -- any decent spotter or pilot can figure it out."

+1

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I'm sure there is a real one out there somewhere but I decided to re-invent the wheel because I had nothing else to do. I have a rudimentary one that I did in Microsoft Works Spreadsheet. I included a knots-miles conversion section.

It may show stupid or how smart I am...I make no claims to fame. Feel free to tear it apart and make suggestions for improvement.

Note the shaded cells shouldn't be changed, unless needed to, because many of them are formulas. I did not lock them purposely so anyone could make their own changes/improvemenets as necessary. You can input your data at the top of the Exit Point calculator Section at the top in the non-shaded cells.

Have fun and give me some input.
My reality and yours are quite different.
I think we're all Bozos on this bus.
Falcon5232, SCS8170, SCSA353, POPS9398, DS239

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Can you save that as an older version? I cannot open it up as it is.
"It's just skydiving..additional drama is not required"
Some people dream about flying, I live my dream
SKYMONKEY PUBLISHING

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Whats wrong with the ole pen, paper, and a calculator(for those people that cant do math in their heads)?

BUT I have an even better one for you that I have been putting some thought into for a while.
Its a computer that ges in the plane that gives the pilot the perfect spot.
how this would work is that it will take wind direction from the time the plane takes off untill it gets to jump run. with this program jump run could be at any altitude bc it will constantly be resetting jumprun as the data poors in. so if people are doing a hop n pop it will give a perfect spot for them based on the winds and altitude at that point. at the same time as you climb to normal altitude it will stil be figuring jumprun for you untill you get to altitude at which point the pilot jst has turn down the line on the screen(jumprun) turn red light on when he crosses the red dot and turn the greenlight on when he crosses the green dot.
Oh and this is very doable but very expensive.

sorry for rambling and Im sure some dude that mojored in english is having a fit right now

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They already have that computer in DoD planes.
Matt

An Instructors first concern is student safety.
So, start being safe, first!!!

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I bet mine is better jk

Did I mention that we have 6 planes running it but for a totally different purpose

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I am not sure how many planes DoD has but I think thay have a version of the computer on all most all of 'em.

What 6 planes and what purpose?

Matt

An Instructors first concern is student safety.
So, start being safe, first!!!

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Quote

What you described already exists, the military has been using it for ages via the stubby pencil method but we also have an excel sheet that does the same thing. However, there are a few things that make this a bit more difficult than you think.

Before I list a few points to consider, I suggest you do a search on "do bad spots really exist". Before there was a file size limitation back then, I posted a few power point presentations that will show you how to do this and also explain things like doglegs and incompatible winds that make using an excel sheet, when either of these two things is present, un-doable.

Also, if you own a Garmin eTrex GPS, there was a jumpmaster feature on it that basically does this, but it is time consuming to use and it uses the military way of determining a spot which is not always desirable or feasible with skydiving operations.

1. As I eluded to above, using this method, be it stubby pencil or excel sheet, you are going to find that the resulting spot (depending on the winds) is a good deal away from the DZ. Most skydiving DZs have a general "pattern" that they fly dependent on the winds that is usually over or close to the DZ. Using distance and direction calculations for determining the spot is always going to put your spot outside of what most consider a "normal" jump run. When I say this, I mean that in some cases if I opened the door and told civilian skydivers to get out on the calculated spot , they would think I was insane and that they would never make it back. This is the biggest reason why this method will not work for civilian skydiving operations, not to mention that it requires updating as the day goes on and is far less forgiving than the way skydiving operations currently operate.

2. Doglegs and incompatible winds. I won't try to explain it here as it would take to long,besides the PPT show explains it in detail and how to compensate for it via the stubby pencil method. With an excel sheet, this is an issue as it will spit out an incorrect set of numbers (trash in, trash out). Also, if using wind directions from 315 degrees to 045 degrees to calculate average wind direction, erroneous averages may result on an excel sheet. To compensate, you must add 360 degrees to directions of 001 to 045 degrees before you plug those numbers into the excel sheet. You also will need to figure for magnetic to true for wind direction and drift as you have to transfer this info to a map to plot it. You also have to figure in for forward throw.

3. This method is not easy to implement and most people can't or won't(or don't have the skills/resources) do it as it takes a good deal of effort beyond what is done in civilian operations, even with the excel sheet.

4. Part of the formula requires that you know the "K" factor for the canopies being used. In skydiving operations canopies vary drastically in some instances. This "K" factor can be adjusted for but it further complicates and increases the likely hood of some people landing off a lot more than what we see now in civilian operations. Again, none of this is taking into consideration the other factors such as exit separation and exit order, which would further make this unfeasible since most people can't even exit the aircraft when the green light comes on without waiting for a few seconds or longer.

I could keep going on but I think that those who are interested will look at the PPT presentation and then see why this really isn't a good idea for civilian skydiving operations.

EDIT to add: This method also requires that the jumpmaster know how to really spot. Not a typical skydiver spot, but actually have the A/C door/ramp open and visually look for a geographical reference point on the ground, identify it correctly and then release the jumpers when over it, not before, not after. Real spotting using this method is an art and requires more than what is called "spotting" in skydiving circles.

The spot is the spot. Whether one chooses to heed the calculations of such an application is their business. And all the extra stuff like "K" factor and canopies is unimportant in the context of this thread. All I want to know is where the spot would be if I want to fall in a column of air from a specific altitude, open at a specific altitude, and drift a round, non-steerable canopy to the target. That's all.

Everything else - like best jump run direction with cross-winds aloft, etc., are not part of this. But thanks for the input.
Chuck Akers
D-10855
Houston, TX

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This would be bad. No more dummy loads.
No more landing with the cows and taken back to the DZ by the farmer's cute daughter.

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Then you would use D=KAV, in two parts.

For Freefall D=3 (the constant or "K")xAltitude (thousands of feet falling reduced- 9K=9)x Velacity (averages of the winds for each thousand foot increment).

or
D=3x9x12 D=324 m This is freefall drift.

For the round Canopy flight

D=25x3 (openning at 3K) x Velocity (average again)

or

D=25x3x10

D=750

Or the spot will be 1074 m from the center of the peas. (based on the tube scenario, not swagging any thing like forward throw or climb out etc. and using a perfect one direction wind chart)

Matt
An Instructors first concern is student safety.
So, start being safe, first!!!

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http://www.digiacom.com/prod_harp/HARP_Home.htm

This is what we use at our dz and it works good.

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Quote

http://www.digiacom.com/prod_harp/HARP_Home.htm

This is what we use at our dz and it works good.

Thats pretty much a copy of what the military excel sheet does minus the map overlay. The military version has space for more altitudes as well.
"It's just skydiving..additional drama is not required"
Some people dream about flying, I live my dream
SKYMONKEY PUBLISHING

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