Digital or Analog Altimeter
We all know there are some hot debates in our sport: RSL or no RSL, AAD dependency, and exit separation are well-known dead horses. Another topic certainly worthy of discussion is the choice between analog and digital altimeter displays. Asking that question will yield a variety of opinions (no surprise there) and will likely be inconclusive.
First, a clarification: this discussion revolves around the altimeter display, not the underlying hardware. Altimeters with mechanical internal aneroid capsules have analog displays; those with electronic pressure sensors can have either a digital or analog display. Now that we have cleared that up...
Analog dial faces of all types commonly have numerical graduations and colored segments to indicate the status of what is being measured. Alti-2’s Altimaster Galaxy, for example, is first graduated in thousand foot increments starting at the 12 o’clock position (zero). There are yellow and red caution zones placed at commonly used altitudes to provide a visual warning at a glance. Digital displays, like Alti-2’s N3, provide a numerical altitude reference. N3 provides a three-digit decimal altitude in free fall and four digits under canopy. So – which is better? It really boils down to three things: familiarity, specific application, and personal preference.
Many skydivers stick to what they learned to use as students. Later in their skydiving career they may choose to “re-train” that familiarity and transition to a digital display. I did so myself when Neptune hit the market nearly ten years ago and have been a huge digital display fan since then.
Application brings a different frame of reference entirely. Let’s take a look at two commonly used analog dials, starting with the temperature gauge in your automobile. My dear old Dad taught me to look at my gauges periodically like a pilot does cross-checks. A quick glance at the temperature gauge should show the pointer dwelling just slightly left of center, or about 40% of its travel. I have no earthly idea what specific numerical data that conveys – I glance at the gauge, my brain processes the placement of the needle based upon my training, and I know that I am good to go! Now consider the gauge on a fire extinguisher which contains a small green segment and a large red segment. A quick glance reveals the pointer dwelling in the green or the red – good or no good. In both of these cases, an analog display is preferable to the way I do business.
What about skydiving? From day one we are asked to apply specific action to specific performance altitudes. As an AFF Student, we may be taught to recognize 5,500 feet on our altimeter to trigger a critical action: wave off and pull. It can be argued that the direct conveyance of that numerical data from a digital display eliminates the need for the brain to convert the pointer’s indication on an analog dial face into numbers for an action to be triggered. If an AFF Student recognizes 5,500 feet on his digital display, it directly sends him into action.
Then there is personal preference. Electronic altimeters with a digital display often have other features like logbooks, timers, and the like that take more time to learn. Some skydivers just love the simplicity of turning a knob to zero the pointer and off they go.
Mechanical/analog altimeters are usually more economical for skydivers on a budget. Electronic devices require power from replaceable or rechargeable batteries; mechanical devices do not. There are several other advantages and disadvantages regarding the mechanism which can also drive personal preference. Factor in accuracy, calibration requirements, form factor, mounting options, ability to read altitude in low-light or darkness, waterproofing, convertibility between visual and audible, and others – the decision becomes more complicated.
So, if you are in the market for an altimeter, or are thinking about switching from analog to digital, I suggest you try them both. Put your trusty Altimaster II in your helmet bag and borrow an N3 from a friend or even your local gear store. Make a few jumps reading digitally conveyed numerical altitude and see what you think! In the meantime, I will be thinking about what advances in technology might be on the event horizon.
John Hawke (slotperfect) is General Manager of Alti-2, Inc. in DeLand, Florida, USA
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Both electronic and mechanical altimeters have their own set of failure modes. The key lies in completely understanding your device, being aware of its known failure modes, and (as you said quite well) are prepared with scenario-based actions to deal with emergencies regarding a device malfunction. I have an electronic AAD in my rig that I am not only very well-acquainted with, but I have also built it into the pre-flight routine of my rig before I put it on. I do something VERY similar with my N3.
Alti-2 experimented with a heads-up display that fit in an Oxygn helmet called "Titan" in the mid-2000s. Frankly, the skydiving market was not ready for that type of product at that time. The challenges for that product were many: viewing angle of the display, visibility in bright sunlight, and rigging (cables) were all pieces to the puzzle. The decision was made to shelf the project. For us, sometimes it becomes a matter of focused priority - we are a small company and do our best to spend our limited resources carefully. Off-the-shelf HUDs made for other sports are starting to make their way into skydiving. With technology available to us now that was not when Titan was in development, perhaps it is time to revisit the idea? After all, we are always working on something....
Well done summary!
I personally absolutely prefer digital altimeters (use an N3 and had neptunes before) but mostly because of their additional features like logbook. Nevertheless, like you described, all the electronic gadgets needs power. So sooner or later you will end up with an electronic device which simply stops working because you forgot to change batteries, or to recharge them. Taking care of this requires awareness someone probably needs more for the important stuff.
So if I use an electronic altimeter, I have to be prepared to a failure and in worst case be ready to e.g. jump without working altimeter. Realising that the good on the ground altimeter just stopped working minutes before exit puts a lot of additional stress on the user. If he is not prepared for this, then I would argue against and instead recommend the good old analoge (we know even they can fail....). This is the reason why I think every new jumper should at least by an analog alti to start with and to delay the decision to go electronic for a couple 100 jumps....
When do we get the heads up displays in our full face helmets? You know the one where the numbers change color from green to yellow to red. This kind of thing should have been around for years by now.
A well thought out personal essay of altimeters as many currently understand things work. I appreciate your efforts, However: " It really boils down to three things: familiarity, specific application, and personal preference."
This is not how our brain works. Research has clearly shown, Posner, Donovan, etc., and including Research done in the seventies that I personally participated in for the DOD, NASA, etc., has consistently shown that pictorial displays "capture your attention,... in stress inducing situations,... significantly more readily than numerical, audible, or text driven information."
The key word here is "Significantly." See Posner attention capture research for a more thorough and complete explanation.
This has nothing to do with "personal preference," or the application or your familiarity with the display! And to make this jump in logic is doing a great disservice to skydivers worldwide.
Very rarely in science do we get such strong evidence that our brains process visual pictures and that that same information can capture our attention more readily than text displays.
I also look forward to the day that your altimeters, the electronic displays, can present a colorful pictorial display, with more attention capabilities, (Think blinking bright red, at a display level above ambient ,...) and then perhaps switching to a more accurate numerical display for the landing pattern, as a possible idea.
BUT until then,... in an emergency situation, numerical displays are at a significant disadvantage as compared with pictorial information.
I think it really comes down to cost of the altimeter. When I learned I learned on an analog one and I think it would be safe to assume that places teaching new jumpers are worried that expensive digital ones will disappear so they purchase the most inexpensive ones.
I think it would be nice to have an analog and digital device in one. What I would really like to see is something like the Galaxy with a little cutout that displays altitude digitally to the left of the red. The Altitrack seems like a really nice alternative to both analog and digital but at the same time it is essentially two different altimeters
100% Agree to both of your points. I remember if doing video, after leaving the AC, I do not look at the alti at all. Neither in Freefall, nor under canopy - if jump and opening goes well (I have an audible too....)
So malfunctioning or missing wristmount Altimeter is mostly not an issue at all - if everything goes well!!
I also have a good number of jumps - does not make it better btw, but I would never want a "novice" to be in a situation where he is not able to reliable check his altitude at any time!!
You are also right that it is very easy to spot your buddys analog altimeter, but it is nearly impossible to spot your buddys digital altimeter. In consequence, this is a point to consider, even if you are very familiar with your digital one.
Altitrack is a good alternative, but it does have all the inherent problems of every electronic device.
Considering all this, I still love my N3... :-)
Analog can also be more easily viewed on someone else in freefal. Take a 4way for instance, I can check my buds analog while still looking into the formation on something like a sidebody.
I also see another trend.....Why use an alti if you have a dytter. Scares me.
@coticj: That is a very good idea. I have personally been using my own custom Excel spreadsheet for years, altbeit with manual data input. I experimented with logbook software, including Paralog, but found that the combination I mentioned works the best for me. I will look into the idea of exportable data N3>>NMU>>Open Source and put it on the list of things to include in future projects if it fits. Thanks very much for the feedback!
@ChrisD: Interesting that you would assume that I was not aware of the scientific analysis of which you speak and the conclusions that came from it. Actually, I have done a lot of homework on the subject and have read summaries of the NASA research as part of my own effort to gain a better understanding on the subject. The science shows clearly that picture-to-action provides a more rapid and effective path for triggering a response.
As a student, if I was simply taught picture-to-action, and was able to carry that technique throughout my entire skydiving career, an analog display would have served me quite well. Point of fact, from day one I was taught to associate action with altitude - a numeric value. In cases when I was able to use picture-to-action, such as beginning my pull sequence when the pointer hit the yellow on my old Altimaster II, the tool was a perfect fit for the job.
As I became involved in more complex skydives, I personally found that a numeric altitude that my N3 provides was a faster and more efficient path to the associated action. When I was an AFF Evaluator, it kept me from having to train myself to associate 5 critical actions with 5 separate pictures and eliminated the time it took to process what my eyes were seeing and convert the picture to a numeric value already associated with each action. It also provided a clear, accurate altitude for me to mentally record Candidates' actions to make an objective go/no-go decision and debrief them on the ground. My fellow Evaluators, and a large percentage of the Candidates, discovered the same.
I will keep using the analog gauges in my car to translate picture-to-action...it works very well as the science has proven. On my wrist I will stick to the digits. I will also continue to educate myself on this subject and others in the hope that I can engage in thought provoking conversations, which was my intention for this article from the start.
I prefer multiple modes of altitude awareness. Wrist mount alti of some sort, and an audible alti to suit. When I started skydiving, I would also wear a chest mounted altimeter. It was GREAT on tracking dives and under canopy. Just look down and it's right there like an airplane instrument on the dash! It is SUPER nice to be altitude aware without much effort. To get crazy about it, use both! A digital wrist mount, and analog chest mount......why not an audible too!?
Be safe, Have fun!
There is one major issue that has not been addressed here.
Went to a boogie, landing on the beach and that was where you packed and waited for the bus ride to the plane. Plane loaded at the airport which was +500 ft. If you were on the 2nd otter load and had to sit to wait for the 1st, your digital alti reset to the airport altitude. So too was your AAD. Everyone was off 500ft except for those analog dial altimeters who were set a 0ft when they landed at the beach.
Digital reset themselves, analog stayed put until you move them.
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