Where am I?
For reasons I won't go into, I've taken an interest in global positioning systems. My first encounter was in a Toyota where the device is built in, or provided as a one thousand pound extra. I find that both wasteful (when you change the car) and unhelpful for instance, when I go out on my bike, or walking. So I started nosying round as I'm wont to do, looking at what is available. I'd seen people with hand held devices, which look both convenient and portable (if battery dependent). The more I read the more conflicting reports I encountered. Omitting geodesic surveying quality devices, the choice seems to lie between either a handheld (basically Garmin or Magellan with other minor contenders) device or an antenna (various forms) connected to a PDA. The former have both map and positional information in highly proprietary formats, the latter are of little use once it starts raining, or you are out for more than a few hours - battery life. In terms of a car based system, I opted for an aerial (SiRF Star III of course - the jargon is yet another lesson in speciality fields) and some software for my laptop. That meant a cigar lighter adaptor for the laptop, always useful I guess. Finally something on which to sit the laptop in the passenger seat, a knock-up in wood did the trick. The maps for the software are line drawings, which are usable with the labels, but nothing like as rich as the Ordance Survey maps I was used to. The classic one inch maps, sorry 1:50,000 scale are available (with a GPS device input) in soft form from memory-map, though rather expensive and lacking a good upgrade path. It appears you need to re-buy the software each time OS upgrades the maps, since they are licenced to use the maps by OS.
The handheld devices? I am basically disappointed. I imagined with a PDA screen quality it would be possible to present an OS class of map with the positional information. It appears the software designers are either greedy or have had too little competition for too long. No ergonomic design, weak functionality and plain paranoid about helping users make use of the data. Put rather too simplistically, the devices seem to present me with a position, are able to save to memory a series of points (tracking a path) and upload (some devices) pre-plotted paths that you want to follow. Great, if you are going to replace a triangulated position with one presented by a processor and satellites. I'd hoped for more in 2005. I'm hoping they will get a shock when some serious competition comes along.
Eventually, having used the car based system, I opted to buy a handheld. These are some of the complaints.
Bottom line, whilst being pleased to know where I am, I remain unconvinced that the current crop of devices are anywhere near the technological potential
The British have a habit of knocking state provided services, be they good or bad. I want to praise one. The Ordance Survey provide a tiny insight into the fascinating (I found) generation and use of mapping data, positioning etc. The have set up a site gps.gov.uk which I found really really helpful! It puts the taxmans site to shame. I have spent hours simply reading the 'tutorials' (I guess that's what they are). It appears to be a class of information I've found sourced by eminantly knowledable people who are also enthusiastic about their subject? Have you met some? No matter what the subject, they seem able to pass on their enthusiasm to others. As I said earlier, the jargon adds another dimension to it, why does entry into all these differing fields require the acquisition of a new vocabulary?
I've been reading about coordinate systems.... here. It is really fascinating. I can't pretend to understand some of it, but it is well (and clearly) written, presents some astounding facts. E.g.
The overall size of the TRF still used for British mapping came to be derived from the measurement of a single distance between two stations on Hounslow Heath in 1784 - using eighteen-foot glass rods! The error thus incurred in OSGB36 is surprisingly low - only about 20 metres in the length of the country.
The network of reference points with known coordinates is called the coordinate Terrestrial Reference Frame (TRF), and its purpose is to realise the coordinate system by providing accessible points of known coordinates. The inference there (apart from the politics of committees throughout the last 300 years) is, to me, the astounding concern for accuracy 300 years ago!
These guys are talking about accuracies of a few centimetres in national posisitioning. I find that amazing. The mathematics of it keeps bring a certain gentleman to mind. Particularly when I start to look at mixing mapping and SVG
Equally, I'm sure this is boring to most, so I shan't continue.
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