I think it’s great for pilots to visit towers and ATC sites, and for controllers to fly along with pilots. During my primary flight training, my instructor, Raeleen Ranger, made a point of getting me up into the tower at CYPK, Pitt Meadows Airport.  It was interesting to see their gear, and invaluable to put a human face on the voices who tolerated my bumbling in, and on, the air. I admire the patience and supportiveness of the controllers at training airports, like Pitt Meadows and Boundary Bay, who give novice pilots a safe place to learn and make mistakes. I was particularly touched when, after I flew my first solo, a CYPK controller was one of the people who came down to congratulate me. (more…)

I’m a big fan of flying, in just about every form. I’m a licensed private pilot. I’ve done skydiving in the past.   I go nuts over airplanes and airshows. I have dreams where I’m able to simply leap in the air and swim (wait, so does everyone else). I enjoy scuba diving and swimming in part because they let me move in three dimensions. My beloved spouse, however, isn’t really excited by any of these pastimes. We have gone scuba diving together. But she finds my powered small aircraft to be noisy, cold, and boring. Flying has mostly been a “me” activity, without her participation. She in turn has her “me” activities that don’t involve me. (more…)

If you haven’t come across It Gets Better, then run don’t walk to the It Gets Better project site. Watch some of the over 10,000 videos contributed by people, from all walks of life, with a common theme: encouraging youth who are being bullied, and perhaps contemplating ending their lives, to believe that life gets better after high school — and that they too should stick around to see it happen. (more…)

Ads Factory, by Romanian developers The Factory,  is a commercial component for Joomla 1.5 which lets you add classified ads to your Joomla site. (My client had me working with version 1.x on Joomla 1.5, but I see there is also a version 2.1 of Ads Factory which is Joomla 1.6 native.) There are quite a few places where Ads Factory includes geographic information: each user record can record a latitude and longitude for that user; each ad can record a latitude and longitude for the advertised merchandise; and there is way to make a “radius search”, i.e. find all ads within a given distance of a user-specified location.

These latitude and longitude values are stored in database fields with name suffixes “X” and “Y”. The user’s latitude and longitude are stored in fields “GoogleX” and “GoogleY” of the Ads Factory user table. Similarly, but not completely consistently, the ad’s latitude and longitude are stored in fields “MapX” and “MapY” of the Ads Factory ads table. The confusion comes in understanding which field stores the latitude, and which stores the longitude.

Latitude is, of course, the signed number of degrees north of the equator of a point on the earth’s surface. It ranges from +90.0 (the North Pole) to 0.0 (the Equator) to -90.0 (the South Pole). Thus, it’s a vertical coordinate. Longitude is the signed number of degrees east of the 0° meridian (roughly Greenwich, England). It ranges from +180.0 to -180.0. My part of North America is 122-123° west of Greenwich, so we have longitudes of -123.0 to -122.0 or so. It’s a horizontal coordinate. This is a well-established convention in many mapping standards.

Tidy Cartesian mathematicians like me use the convention of (X,Y) coordinates, where X is the horizontal coordinate and Y is the vertical coordinate. This is a well-established convention in geometry and graphics (though there are some exceptions).

My first interpretation of Ads Factory field names like  “GoogleX” and “GoogleY” was to interpret them according to the Cartesian convention: X is horizontal, and so stores longitude, while Y is vertical, and so stores latitude. Thus (MapX, MapY) would be (longitude, latitude), the opposite of what one expects from mapping. Odd. I was surprised to find some parts of the code storing latitude in X (the horizontal coordinate!) and longitude in Y (the vertical!), which was surely a bug. I was horrified when it appeared that every part of this code had the same bug!

Then I understood the convention. Ads Factory’s developer appear to have used the (X, Y) convention to indicate just the order of the coordinates, but not their Cartesian meaning.  (MapX, MapY) means (latitude, longitude), as is conventional in mapping.  X is the vertical coordinate, Y is the horizontal coordinate, in the Ads Factory context. If you remember that X means “first”, not horizontal, and Y means “second”, not vertical, the Ads Factory field names are self-consistent, and the code uses them correctly.

I haven’t seen any Ads Factory documentation which explains this, so I hope this note will help some of you Ads Factory enhancers who are using these fields.

Postscript: what did my client ask me to do with Ads Factory for their site?  Modify the radius search to search around the user’s latitude and longitude, instead of a location the user enters. Also, to sort the keyword and category search results by distance from the user. Quite straightforward to do, though it requires customisations to the Ads Factory code that have to be re-done everytime one upgrades the Ads Factory component.

I first came across Derek when researching what people were learning about digital legacies: what happens to one’s online persona and works when one dies.  Derek apparently coined the term “digital executor”, the person who has the responsibility to take over all one’s blogs and accounts and presence on the net on one’s death. I think it is a brilliant term. (more…)

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Eclipse Web tools editors (2.0.1) requires plug-in "system.bundle"
Eclipse Data Tools (1.5.1) requires plug-in "system.bundle"

When I would start up EasyEclipse (version 1.3.1 for Mac OS X, with Python, C++, Java, PHP and more support added), it would tell me that I had some outdated components, and offer to update them for me.  But when I opened the menu item Help… Software Updates… Manage configuration, I would get the ominous error alert:

“The current configuration contains errors and this operation can have unpredictable results. Do you want to continue? [Cancel] [OK]”.

I wasn’t able to  find documentation about this problem specifically. (My purpose in writing this is to help others benefit from what I learned.)

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Nearly two years ago I came up with a handy quick reference to current Canada Post and USPS postage rates for basic letters between the USA and Canada. Last spring it was polished enough that I posted it on my web site. I just now updated it to reflect the Canada Post rate increase which took effect on 17. January. You can find it at http://jdlh.com/en/pr/postage_card.html.

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I recently looked for quantitative data about space efficiency of UTF-8 and UTF-16, and couldn’t find very much. Engineering discussions about storage efficiency are better informed by quantitative data than by opinion and supposition. I want to give one morsel of quantitative data more visibility, and clarify this issue. (more…)

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