Friday, November 07, 2014

Geo Referencing

You have at some point probably seen a movie or a television show, usually for children, that uses a gimmick where a story in a book comes to life, or morph into the action of the show. Usually the pages of a book are shown on screen, with text introducing the story, and then a picture. The picture becomes live action, or perhaps the pictures move around in the text. In a movie it's a sufficiently common device that you know if it starts that way, the movie will end back on the printed page with the ornate words The End. But imagine if you were reading a regular, real book. A familiar reference book whose fonts, diagrams, and footnote style have so long been part of your life that you know exactly what to expect of it. Now imagine that a picture or diagram in that book, the one you are holding in your hand, comes to life and starts explaining itself. That's how my introduction to approach plate Geo Referencing went.

An approach plate is a diagram showing an airport runway and the procedures, points and aids associated with navigating an airplane to a point in space from which a safe landing can be performed. If shows the plan view and the side view, with symbols showing where and how to turn, minimum altitudes for each sector and part of the approach, distances, magnetic variation, and type of lighting. It tells you the frequencies for ATC, how much to add to your minimum altitude if using a remote altimeter setting, and has an effective date. The Canada Air Pilot for each region, the physical book in which these things are published is reprinted with changes every 56 days. Most plates don't change from one revision cycle to the next, but the whole CAP is reprinted. When the new one comes you strip the coil bindings off the old one and toss the pages into the recycling. You can tell there's no change if the new plate has the same effective date, worth looking at in case you have inadvertently memorized some data that has changed.

With the Fore Flight electronic flight bag, these approach plates are replicated on the iPad. Instead of paging through the coil-bound CAP trying to guess whether a particular airport will be alphabetized under its own name, or considered a sub-plate of the larger nearby airport, you hold your finger on an airport displayed on the iPad chart until a box comes up, showing all the airports that your stubby finger could reasonably have been aiming at. Tap More next to the one you wanted, then Details then scroll down to Procedures and you can tap Approach and select the approach plate you want. I haven't done a timed test from pulling the iPad or CAP out of the map box, to looking at the desired plate, but I think the iPad is faster. The paper one is easier to read in bright light conditions, even with the iPad turned up full, but in dim light the self-illuminating iPad is great, until it is pitch black dark, at which point it becomes too bright, even if you follow the instructions and turn the brightness to minimum in settings before dimming within the app.

Either way I get the familiar approach plate, very carefully replicated. It's possible to zoom into the iPad ones to read little numbers, easier than pulling out a magnifying glass, but you have to be careful not to leave it zoomed in, when that moment comes on the approach where you glance back at the plate to confirm the minimum descent altitude, and the data isn't on the screen because you zoomed in to see if that waypoint was spelled with an F or a B. A hundred feet above MDA is not a good place to have to pinch or scroll a screen.

The first time I used the iPad for an approach, I had the conventional paper chart and the iPad both out, and it was VMC. I briefed the approach, flew direct the cleared fix and then eeep! the approach plate came to life. A symbolic airplane representing my position appeared on the screen in the position where I actually was. Even though I have used moving maps for years, the appearance of a moving you-are-here dot, Fore Flight calls it "ownship position" on the plate was freaky exciting magic. Ten years from now pilots will stare at old approach plates in puzzlement, unable to situate themselves mentally. This is a huge benefit for situational awareness. It even switches automatically to the taxi diagram and shows me where I am on the airport after landing.

I learned that this was called Geo Referencing a couple of days ago, from an error message. The app told me that Geo Referencing was not available because the plates were not current. What? These are valid until November 13th. (And the error message came up in October). I think American charts are on a 28-day cycle, so the app auto-expired Canadian stuff after that time period. I brought the iPad into the hotel to try and update them. It's just downloading the same set again, I'm sure, but this is hotel internet. It hasn't worked in all the time I've spent writing this blog entry. Why did it not update everything before I left when I selected "pack" for the flight out here? There are a number of things that Fore Flight doesn't get quite right for Canada, and I haven't found a bulletin board or user forum where these things are discussed, to determine for sure whether it is the product and not me who is missing something. I now know that the iPad has to be updated at the same time as I update the GPS database (which comes from the US, on a 28-day cycle).


Frank Ch. Eigler said...

(AIUI, geo-referencing is only the process of converting the coordinate system between the map raster imagery and the real world latitude/longitude. The ownship overlay part is a separate subsequent part.)

Mark Zacharias said...

Your getting to use a fairly new feature for us Canadians!

Sarah said...

It is just like magic, isn't it?

FWIW, I've found foreflight very responsive to questions or comments. . Check their support info the an email address.

Anonymous said...

Of course the database must be updated regularly - and best not from "Hotel WiFi." A one-week expired page is better than no page. Noting your First Use and having the current paper plate at hand (perhaps strapped to the other leg?) was a brilliant choice!

D.B. said...

The best way to get customer service from ForeFlight is via FaceBook. I asked them a question about running it on an old iPad 1 once they discontinued supporting the older iOS that the 1 runs, and got an answer within a few minutes.

Aluwings said...

You can use Foreflight with your xplane flight simulator as well for practice.

Anonymous said...

It has been a month. Are you OK?

Aviatrix said...

GC: a one-week old plate would certainly be better than no plate, especially given that the old plate was legally valid for another 28 days, but Foreflight refused to serve it to me.