06.23.09
Posted in Development, complexity at 10:17 am by Twm
I’m doing some work with location based services at the moment. A colleague told me of some of the problems they had had with the software. One was related to the SkyHook system. This is the system that Apple used and helps to improve the speed of acquiring a fix by mapping the location of Wifi hotspots and cell towers.
the app would for the most part correctly report the position but during field testing- say when heading down the M25 – it would occasionally report the location as being back in central London. This erratic behaviour was a bit of a puzzle to the the engineers until they discovered that National Express have been installing Wifi access points on their buses.
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05.06.08
Posted in Development, Graphics, complexity at 11:00 am by Twm
My head hurts. For some reason the mobile industry loves to confuse something really simple like a screen sizes.
There are three aspects to screen size.
- Pixel dimensions – on an LCD display, this is simply the physical number of columns and rows of pixels which make up the display.
- Resolution - Pixels per inch/cm. Two values for x,y tell you how far apart the rows and columns of the display are from each other, the density.
- Display size – A ruler measure the physical width and height of the screen.
It’s possible to have a 1024×720 display the size of a postage stamp if the resolution is very fine.
This can get confusing, but explicitly using “Pixel dimensions”, usually clears up any misunderstanding. The problem is that pixel dimensions are often specified in esoteric video terms such as 1/4VGA. Here are some of the “resolution” labels which I’ve encountered at work in the last week.
|
Pixel Dimensions
|
Width
|
Height
|
Number of pixels
|
| QCIF |
144
|
176
|
25344
|
| QVGA |
320
|
240
|
76800
|
| CIF |
352
|
288
|
101376
|
| 1/4HD 720p |
640
|
360
|
230400
|
| VGA |
640
|
480
|
307200
|
| D1 |
720
|
480
|
345600
|
| HD 720p |
1280
|
720
|
921600
|
The names are a mish mash of video standards and display standards and the disjointed nomenclature also makes it hard to compare dimensions. I forget if a QVGA is larger than CIF, or a VGA larger than 1/4HD.
I wonder if we could save a lot of hassle and just use the actual numbers. “320×240″ is not that much more to write than QVGA and has the advantage that landscape orientation can be indicated by switching the numbers to “240×320″.
Crazy diagram: - Wikipedia::DisplayResolution
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12.09.07
Posted in Development, Treemap, c++, complexity at 4:46 am by Twm
In a previous posting, I desribed a method for extracting LOC (lines of code) statistics from a large code base.
I’ve been playing around with Universtity of Maryland’s treemap visualisation tools. For those who don’t know what a Treemap is, the site has some good video tutorials or just google. There is a little bit of a learning curve to understanding and using them
Tremaps were invented by Ben Shneiderman (yep, same guy who created the Nasty-spiderman diagrams as we used to call them in school). Shneiderman wanted a tool to quickly visualise the large clusters of files on hard disk to find out where his space was really being wasted.
The use of Treemaps have extended to other domains with varying degrees of success, and my interest in treemaps was recently rekindled on seeing Tim O’Reilly use Treemap to visualise trends in the book market segments on his blog.
If we group LOC counts for each file by their directory hierarchy then it’s possible to visualise the components of a System in terms of their LOC contribution to the overall code base.
It’s a fascinating exercise. The picture below shows the Treemap for a multimillion line code base. (Note that I’ve anonymised the data by taking an MD5 of the strings, so it looks a bit less friendly than the real view).
Read the rest of this entry »
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