Any question answered...

Using https://community.esri.com/groups/coordinate-reference-systems/blog/2017/10/05/haversine-formula I get:-

haversine( [ 51.4579567525874, -3.1788177379969 ], [ 51.46874938786769, -3.1642846489419014 ] )

Distance: 2011.784 m
Distance: 2.012 km

Thanks a lot! Did you work that out? This calculator gave me 1.566km.
Coordinates were straight out of Google Earth Studio.

For the distance it's probably overkill, and I could assume it was on a flat plane.

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It was just a random google, I'd try a few more to confirm things first!

(But I knew the term "haversine formula" from messing with GPX files.)

Haversine should give you great circle distance, it won't be a direct straight line between the two points.

Ah, the script I had expected Lon/Lat and I was giving it Lat/Lon:-

haversine( [ -3.1788177379969, 51.4579567525874 ], [ -3.1642846489419014, 51.46874938786769 ] )

Distance: 1566.475 m
Distance: 1.566 km

OK, cheers. for the purpose of such a short distance I'm going to assume they're the same,

"
The haversine formula is a very accurate way of computing distances between two points on the surface of a sphere using the latitude and longitude of the two points. The haversine formula is a re-formulation of the spherical law of cosines, but the formulation in terms of haversines is more useful for small angles and distances.
"

Sticking 90,0 and -90,0 in there I get:-

haversine( [ 90, 0 ], [ -90 , 0 ] )

Distance: 20015086.796 m
Distance: 20015.087 km

Which is half the circumference of the Earth. (If it was using straight line distance it would give me the diameter of the Earth).

Is there a forum approved 23c tyre for riding during the zombie apocalypse? Gators or marathons, or anything else I should be aware of?

Panaracer ribmo or Maxxis refuse

If I wanted to find someone to come to mine, pack everything up (40 moving boxes) and move those plus the sofa and two bikes to a self-storage unit 100 yards away without stealing/breaking everything... where would I look?

I've got a 26" mtb frame and forks, thinking of moving 27.5 tyres onto it and buying a 2nd hand sus fork. Am I best off getting a 26" fork or 27.5? Or am I doing it all wrong

am I doing it all wrong

You're very unlikely to fit a 27.5" tyre into the back of a 26" frame. If you solve that problem then a 27.5" fork will deal with the front and you'll just be left with a bike with about half an inch too little BB drop

Want to plug newer laptop into my older TV.

Laptop has HDMI output and TV has SCART, VGA, Component, Composite, S-Vd inputs.

What's the best adapter to use? I was just going to get a HDMI-VGA one but is there any advantage disadvantage to sending laptop to component video or s-video?

is there any advantage disadvantage to sending laptop to component video or s-video?

VGA and component are basically the same but with different connectors, you shouldn't see any difference. S-Video is worse as it converts the three components into two, so you lose bandwidth in the chrominance, also if your source is RGB there will be quality loss in the conversion to YUV. Composite is worst of all as it has to create an analogue multiplex of all the signals to send down one wire.

VGA it is then as those are cheaper adapters and what it's currently using via the old craptop. Ta

Short version: I need a recommendation for an e-card provider that can work by sending a link for contributions out (rather than sending everyone's email to the card provider).

I need to send a card to a colleague in a different office because they're off on parental leave. The usual procedure is to ask someone in their office to get an actual card and then ask someone from each office to collect, scan and send messages to that person who collates and prints them for inclusion in the card. Obviously that can't happen due to everyone working from home. I want to give everyone a chance to put a message in the card, but I will not send everyone's work email address to an e-card company. Does anyone know of a company that produces e-cards but does so by sending a unique link out to multiple contributors, rather than asking for everyone's email?

You may be over-solutionising this. Why can't you just get everyone to email their messages to one person with a home printer, who prints them and sticks them in a physical card?

I've got a Surface Book that only has USB and USBC ports. I'm trying to connect it to an Acer monitor using the following chain of cables:

Surface
USBC to Mini Displayport
Mini Displayport to HDMI
Monitor

The Surface doesn't detect the monitor. I've tested the MiniD to HDMI with a different laptop and that works fine. Is there a way that I can establish whether the issue is the USBC to MiniD cable or a config problem on the tablet/monitor? My other USBC device is a Google Nexus 5X.

Obviously getting a replacement cable will be tricky at the moment, so I'd like to explore all config-related issues first.

AFAIK You can't chain these kinds of adapters like that. They work by telling the computer to generate an HDMI/DP/whatever signal and the adapter just provides the right physical socket. I don't think the "I want HDMI" message makes it across the MiniDP step back to the computer.

So you need to persuade the Surface to output an HDMI signal, which I think it'll only do if you plug a direct USBC-HDMI adapter into it.

You need a USBC to HDMI cable or HDMI cable with a separate USBC adapter.

https://www.amazon.co.uk/gp/product/B07MCP3SP8/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1

Thanks @grams @Sumo, that makes sense. I figured since the USBC to MiniD was male-female (like the one in the picture) it was effectively a USBC adapter even though it had some length to it. I'll just get the one cable.

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• s-l225.webp

What volume of air at normal atmospheric pressure is needed to fill an inner tube - a 29er MTB one for example?

Volume of the tube is something like 4.8 litres.

Atmospheric pressure is about 15 psi. If you inflated the tyre to "30 psi" on the gauge the internal pressure would actually be 45 psi absolute. By the ideal gas law you have 45/15 = 3 times as much air.

Therefore a tyre contains 4.8 * 3 = 14.4 litres of air.

(plug in your own numbers as necessary)

For a diameter D and a cross section diameter d, the volume is π²d²D/4

In the case of an inner tube, D is approximately the bead seat diameter plus the cross section diameter, so a 50-622 tube would be

π²×50²×(622+50)/4 = 4145233mm³= 4.1 litres

So I could make a one shot bike pump with a chamber size of somewhere between 4 and 14 litres.