Re: [LEAPSECS] What I do. What do you do?

From: Ed Davies <ls_at_EDAVIES.NILDRAM.CO.UK>
Date: Wed, 29 Jan 2003 15:12:41 +0000

Rob Seaman wrote:

> Perhaps it would help our discussions to simply describe our professional
> (or otherwise) connections to UTC and other precision timing issues.

Excellent idea.

I'm a freelance programmer based in High Wycombe, England. Over the last
few years I've worked on a quite a lot of geographical related software
(data preparation for the Ordnance Survey Interactive Atlas of Great Britain
CD and AutoCAD based software to help with designing aircraft instrument
approach procedures) and also, more relevant to this discussion, data
logger devices used for scoring various sports. The first were loggers
used to record the output of GPSs for gliding (I fly gliders and
aeroplanes in my spare time) which were then adapted for use in motor
racing and sailing. Most recently we've done some loggers which read
RFID tags attached to motor cyclists for scoring off-road events.

More generally, I have a lot of interest in the design of programming
languages and standards. A lot of what Ken Pizzini wrote in the first
two paragraphs of his posting on this subject also applies to me. I
thought of quoting those paragraphs directly but I'll just use one

> I have a
> strong appreciation of the value of a good standard, and likewise a
> strong disdain for any standard which I can recognize as poorly put
> together.

For good practical reasons but also as an exercise in standard writing
I've been having a go at defining a format for geographical positions
in contexts such as XML documents. Have a look at:

While I'm not very serious about it I have a more-than-average interest
in amateur astronomy. Two of my friends have reasonable size telescopes
(8" and 11") which I go and peer through from time to time. I've
been following with interest their experiments with motorizing these
and with use of webcams with extended exposure times. I do some
satellite watching - it was a mention of the campaign to drop leap
seconds in the SeeSat-L list that brought me to this list.

Here's the first paragraph of a message I posted to SeeSat-L in July
last year:

> My first thought was that the idea of dropping leap seconds was
> potty but having read a bit about it and reflected on the requirements
> and knowledge of different users I'm coming round to the view that
> it might not be such a bad idea.

My general concern is that currently most software neglects leap seconds
but that in the future, as systems become more tightly networked, this
will not be possible.

For example, the aviation industry is moving (slowly, as is understandable)
towards a new generation of communication, navigation and surveillance
systems which will be much more dependent on GPS and the like. In
particular, GPS time will be used for many functions such as allocation
of time slots for transmissions on VHF and UHF frequencies. Software
will, in many cases, run on standard PCs. (There a radar-like system
running on Microsoft Windows systems on trial in Sweden and the FAA
has somebody looking into the use of Pocket PCs for in-cockpit displays
in light aircraft).

GPS is widely used in cars, boats, light aircraft and so on. It's
use will become more tightly integrated with other systems.

The overall result is that there will not be a simple distinction
between "precision" timing applications (which need to know about
leapseconds and so on) and "non-precision"/"civil" applications
which can ignore them. The two will co-exist on the same machines
in many application areas - and often in the hands of users who
don't want to have to care about the difference.

(I'm using "precision" pretty loosely here - meaning anything that
cares about time to an accuracy of better than about one second,
never mind the nano second level).

If we are to continue with the application of leap seconds to civil
time then there is a need for a huge education program (particularly
of programmers) and some careful thinking to make sure that
"precision" applications can get the information they need while
existing naive software doesn't get messed up. My worry is that
the long term cost of this effort will be neglected because it is
widely distributed and not accounted directly.

Ed Davies.
Received on Wed Jan 29 2003 - 07:14:52 PST

This archive was generated by hypermail 2.3.0 : Sat Sep 04 2010 - 09:44:54 PDT