Sailor goes in circles

In the quirky section of the news was this story about a sailor going in circles around the Isle of Sheppey. It seems he was trying to travel from Medway to Southampton by following the coast of England and keeping the coast to his right, and with no navigational equipment. He ended up doing laps around the Isle of Sheppey in the Thames estuary until his fuel ran out and he had to be rescued.

After I had finished chuckling over the news, I wondered about the geography of the incident. How could he not have realised that he was circling an island? How did he enter the loop in the first place? If you look up Sheppey in Wikipedia and look at a map you will see that it's a 97 sq km island separated from the main island of Britain by a narrow channel on the Thames estuary side. So it would have been obvious going out that it is a channel not to be entered. Or perhaps, the channel entrance was not visible. However on the other end of the channel near Whitstable, the channel opens up broadly to sea. So it was not obvious to him that he was entering the channel.

He would have passed under A249 bridge though and it should have been obvious on the second round that he was going in circles. Or even before then, when passing Sheerness for the second time.

Incidentally I recognised the name Sheerness. It's where the ferry from the Vlissingen on the Hook of Holland deposited me the first time I visited the UK. Obviously this was in the days before the Chunnel. Wikipedia shows that there is no such service now.

Puppy Hills

The other day a friend texted me to meet at Puppy Hills. The message ended abruptly there. I thought for a moment and realised what had happened. Puppy is a textonym of Surry in T9 predictive text. My friend had tried to correct it and had hit the send key instead.


That gave me an idea for a crime thriller premise. The murder victim manages to send off a last SMS mentioning Puppy Hills. The savvy PI works out that Surry Hills was meant and this clue moves the story forwards. If any crime fiction author is reading this, you're welcome to this idea. <grin>


PS: There is another textonym for puppy which is not a word you use in polite company. If you can't figure it out, don't worry, stay innocent.

You know you are spending too much time on computers when...

You're reading a book and you want to type Ctrl-+.

How to make your own passport photos

This tip applies to Australia. You may be able to adapt these instructions for your country.


The reason I did my own passport photos was because a photo shop will charge you several dollars for a set of photos. You can get digital prints made for less than $0.20. That's a tremendous savings factor.


First of all, acquaint yourself with the requirements for Australian passport photos. Keep these guidelines in mind. Your photo will be rejected if you do not adhere to the guidelines.


Get the best digital camera available to you. A good lens is more important than lots of megapixels. Pose in front of a neutral coloured wall and have a friend take a selection of photos of you, to have a better chance of getting a good shot. It's best if the photos are taken from mid-distance, using optical zoom to centre on your face, to avoid wide-angle distortion.


A normal 15cm x 10cm print can hold 8 photos of 37.5mm x 50mm, so that is the target size. The aspect ratio is 3:4.


In the following I assume a computer with GIMP, NetPBM and JPEG tools (e.g. Linux). If you have some other operating system, you'll have to adapt the instructions for the tools available to you. Upload the photos and pick the best shot. If none of the shots are suitable, go back and redo the shoot.


When you have a good picture, open it in GIMP. Make any necessary adjustments in the contrast and brightness. Select an aspect ratio of 3:4 or 0.75 in the crop tool and select the head region so that the head height is between 0.64 and 0.72 (32mm to 36mm in the final photo). This comes from the guidelines.


Make a note of the size of the cropped region, then save it in PPM format. Say it's is called mugshot.ppm and the size is 1500 pixels by 2000 pixels. The following shell pipeline replicates it to make a 4x2 matrix, i.e. 6000 pixels by 4000 pixels, then scales it down by half so that the printing machine doesn't think the camera has 24 megapixels, in case it cannot handle such a high resolution, and finally compresses the PPM to JPEG.

pnmtile 6000 4000 mugshot.ppm | pamscale 0.5 | cjpeg > mugshot-4x2.jpg

Now take that JPEG to your photo shop in the usual way (USB flash key, CD-RW, upload) and have it printed. You can then slice the photo matrix with a rotary cutter if you have one, or with care, a pair of scissors.