Oct 10, 2015, 4:43 PM
Post #1 of 3
L/D Magic is now FREE!!!
The price for the app is now moved to the optional Flight Data Recorder in-app purchase, so that more people can try the app and see if it works for them or not. It's a very complex app I wrote to fulfill my vision, it's not a plug-and-forget, but rather a serious scientific instrument.
It can be used EITHER on a pole/vane OR in pocket, but in latter case requires an external GPS for high quality signal and high sample rate. Currently, Dual XGPS150A (Bluetooth) and Emprum UltiMate GPS are supported at 5Hz. Other external units should work, too, but most likely only at 1Hz.
As I shifted my programming attention to cross-platform development in C# (while L/D Magic was written in Objective-C), it hasn't been updated in a while, but the update is coming with iOS8+ support, compatibility with 10Hz sample rate for Dual XGPS160, bug fixes, etc.
L/D Magic now supports 10Hz sample rate with Bad Elf GPS Pro and Dual XGPS160, as well as 5Hz with Dual XGPS150A and Emprum UltiMate GPS.
The app is iPhone-only. For Android and Windows phones, I have a simplified app called L/D Vario, see this thread. Note that while L/D Magic has two modes of operation - one with the phone mounted on a vane in free stream, using accelerometer to measure L/D, and the other with the phone in pocket, using high-speed external GPS; L/D Vario works only on a vane. Here's an example with LG G Watch R:
(Also, a fast built-in pressure sensor is highly desirable to get accurate measurements of the polar curve speeds. LGGWR has one at 90Hz; the champion as of now is Nixon the Mission smartwatch with 165Hz sample rate reported by a user.)
Another difference between L/D Vario and Magic is that the former does not require exit at exact moment of "c-ya!" count like the latter; it works continuously. L/D Magic requires precise start because it needs a start point to integrate WSE and run Kalman filter; thus it's more suited for BASE as it's hard to exit at exact moment from the airplane.
Vane: you need to make one yourself for your device. It needs to be balanced neutrally on its axis and mounted on a pole at least ~2ft from the belly (helmet is not a good place for this) so that the angle of the relative wind hitting the vane is the same as the angle of your velocity relative to the air mass (i.e. the vane is in true free, undisturbed stream). Like this:
Any questions about the use, feel free to ask here or by email in my profile.
WSE are an azaming (i.e. so amazing that can't even spell right) phenomenon - they're so simple to derive that it's like kicking a rock with your foot and boom! it splits in half and a 100-karat diamond rolls out of it! And in 10 years, I derived so much useful stuff from it that it fills several Moleskins with yet unpublished gems waiting their time:
And it shows no signs of depletion. For example, recently I found a more accurate estimate of the L/D necessary to achieve maximum sustained horizontal speed: 1.3 for wingsuits capable of max L/D of ~3.0 (the previous result from 10 years ago was square root of 2; it turns out this is for infinitely high L/D) - useful for those participating in speed competitions. The recent idea of FAP (Fast, Accelerated Proximity) was also fueled by WSE.
It almost feels spiritual: it can't be so simple, so beautiful, so powerful... but it is! I don't know if there's God or we're living in a computer simulation run by another civilization, but to me WSE ring that tiny bell that it's all not random... all these big walls, diving boards as if specifically made for BASE... there must be The Old Dude in White Wingsuit Sitting on a Cloud watching for us!
Beeeeeeeeeeeeeeeeeeeeeeeeeeer and azaming flights, everyone!!!
However, for Android users it will require a bit of work: unfortunately, it's not possible to make a paid app on Play Store temporarily free; free is permanent. So, you'll need to use a promo code. I've generated 357 promo codes (out of 500 allowed for the quarter) - remember, 3.57 is a magical L/D, thus, 357 codes. The list of promo codes is attached. If one doesn't work on December 7th, it means it was taken already, try a different one.