How do they do that? long/lat in database then measuring distances between

[Jayne Wolps]

Hello
I wonder if anyone can help.

I would like to know how certain sites:
http://aboutbritain.com/ArundelCastle.htm, and
http://travel.knowhere.co.uk/place/+bristol-0/ manage to put approx mile
distances between their listed towns and attractions.
You will see it on the knowhere.co.uk site on the right side where they list
nearby towns and on aboutbritain.co m you will see it where they list other
nearby attractions and hotels towards the bottom of the page.
I guess they store longitude/latitude in their database so they can pinpoint
each attraction/hotel ETC, but what then. How do they calculate distances
between those hotels and attractions and other towns?

Also, the database on my site has alot of places stored but with postcodes.
Is there a way of converting postcodes into approximate long/lat positions?
Like a universally available table or something?

My programmer is back tomorrow from his holidays and I'm trying to gather as
much information about 'how it's done' so I can get a similiar system
implemented on my website. My new website will be describing thousands of
British villages and storing them in a mySQL database and I'm looking at
ways of listing the nearest attractions to them. The site uses alot of php.
If my programmer does not contact me on his return (he often obsconds for
lengthy periods) I will be looking for someone who can do this sort of work
and other work. Must be reasonable! and reliable!

If anyone can help I'd be most grateful.

Kind Regards,
Jayne Wolps

[Kevin Thorpe]

Re: How do they do that? long/lat in database then measuring distancesbetwee n

Jayne Wolps wrote:[color=blue]
> Hello
> I wonder if anyone can help.
>
> I would like to know how certain sites:
> http://aboutbritain.com/ArundelCastle.htm, and
> http://travel.knowhere.co.uk/place/+bristol-0/ manage to put approx mile
> distances between their listed towns and attractions.
> You will see it on the knowhere.co.uk site on the right side where they list
> nearby towns and on aboutbritain.co m you will see it where they list other
> nearby attractions and hotels towards the bottom of the page.
> I guess they store longitude/latitude in their database so they can pinpoint
> each attraction/hotel ETC, but what then. How do they calculate distances
> between those hotels and attractions and other towns?[/color]

Pythagoras comes to the rescue here:
distance from (ax,ay) to (bx,by)
= square root ( ((bx-ax)^2) + ((by-ay)^2) )
[color=blue]
> Also, the database on my site has alot of places stored but with postcodes.
> Is there a way of converting postcodes into approximate long/lat positions?
> Like a universally available table or something?[/color]

This site has a table of postcode locations

http://www.jibble.org/ukpostcodes/

[Chung Leong]

Re: How do they do that? long/lat in database then measuring distances between

Uzytkownik "Kevin Thorpe" <kevin@pricetra k.com> napisal w wiadomosci
news:403a34d8$0 $12601$afc38c87 @news.easynet.c o.uk...[color=blue]
> Pythagoras comes to the rescue here:
> distance from (ax,ay) to (bx,by)
> = square root ( ((bx-ax)^2) + ((by-ay)^2) )[/color]

I wonder if the sum of the difference in x and the difference in y wouldn't
better approximates the distance people actually would need to travel,
considering that city streets are usually arrange in a grid.

[Trevor Smith]

Re: How do they do that? long/lat in database then measuring distances between

On Mon, 23 Feb 2004 17:16:23 +0000, Kevin Thorpe <kevin@pricetra k.com>
wrote:
[color=blue]
>Jayne Wolps wrote:[color=green]
>> Hello
>> I wonder if anyone can help.
>>
>> I would like to know how certain sites:
>> http://aboutbritain.com/ArundelCastle.htm, and
>> http://travel.knowhere.co.uk/place/+bristol-0/ manage to put approx mile
>> distances between their listed towns and attractions.
>> You will see it on the knowhere.co.uk site on the right side where they list
>> nearby towns and on aboutbritain.co m you will see it where they list other
>> nearby attractions and hotels towards the bottom of the page.
>> I guess they store longitude/latitude in their database so they can pinpoint
>> each attraction/hotel ETC, but what then. How do they calculate distances
>> between those hotels and attractions and other towns?[/color]
>
>Pythagoras comes to the rescue here:
>distance from (ax,ay) to (bx,by)
> = square root ( ((bx-ax)^2) + ((by-ay)^2) )
>[color=green]
>> Also, the database on my site has alot of places stored but with postcodes.
>> Is there a way of converting postcodes into approximate long/lat positions?
>> Like a universally available table or something?[/color]
>
>This site has a table of postcode locations
>http://www.jibble.org/ukpostcodes/[/color]


Jayne

PostCodes won't help as they are not arranged in that way in the UK. I
think a better and much more accurate way would be to use grid
coordinates. The Ordinance Survey grid is arranged in Eastings and
Northings and is measured in metres so a straightforward search in a
database for all locations within a rectangle around your location is
fairly easy. The distance can be calculated using simple trig. Lats
and Longs could also be used but the maths get a bit tricky. You can
also pass on the grid reference so that users can find the location on
their map or provide a button to link to a mapping web site. If you
want to add a map to your web pages, try http://www.map24.co.uk

regards
Trevor

[Centurion]

Re: How do they do that? long/lat in database then measuring distances between

Kevin Thorpe wrote:
[color=blue]
> Jayne Wolps wrote:[color=green]
>> Hello
>> I wonder if anyone can help.
>>
>> I would like to know how certain sites:
>> http://aboutbritain.com/ArundelCastle.htm, and
>> http://travel.knowhere.co.uk/place/+bristol-0/ manage to put approx mile
>> distances between their listed towns and attractions.[/color]
>
> Pythagoras comes to the rescue here:
> distance from (ax,ay) to (bx,by)
> = square root ( ((bx-ax)^2) + ((by-ay)^2) )
>[color=green]
>> Also, the database on my site has alot of places stored but with
>> postcodes. Is there a way of converting postcodes into approximate
>> long/lat positions? Like a universally available table or something?[/color]
>
> This site has a table of postcode locations
> http://www.jibble.org/ukpostcodes/[/color]

Note quite. Over VERY short distances (<50km or ~30mi) pythagoras is OK,
but keep in mind LAT/LONG coordinate system is essentially a polar system
in 3 dimensions (pythagoras is planar in 2 dimensions). Google the whole
lat/long distance thing. There are plenty of sites showing the mathematics
to achieve acurate distances between 2 lat/long's - I've seen the raw
formulae and various implementations from MS-Excell to C/C++ and even PCM!

James
--
Fortune cookie says:
Oh yeah? Well, I remember when sex was dirty and the air was clean.

[R. Rajesh Jeba Anbiah]

Re: How do they do that? long/lat in database then measuring distances between

"Jayne Wolps" <jaynewolps(nos pam)@hotmail.co m> wrote in message news:<c1cv1b$92 0$1@hercules.bt internet.com>.. .[color=blue]
> Hello
> I wonder if anyone can help.
>
> I would like to know how certain sites:
> http://aboutbritain.com/ArundelCastle.htm, and
> http://travel.knowhere.co.uk/place/+bristol-0/ manage to put approx mile
> distances between their listed towns and attractions.
> You will see it on the knowhere.co.uk site on the right side where they list
> nearby towns and on aboutbritain.co m you will see it where they list other
> nearby attractions and hotels towards the bottom of the page.
> I guess they store longitude/latitude in their database so they can pinpoint
> each attraction/hotel ETC, but what then. How do they calculate distances
> between those hotels and attractions and other towns?[/color]

- http://distance-calculation.com/Dist...alculation.asp
- http://www.phparchitect.com/sample.p...show=316&mid=9

HTH

--
"Success is not what you achieve, but it is what you die for"
If you live in USA, please support John Edwards.
Email: rrjanbiah-at-Y!com

[Kevin Thorpe]

Re: How do they do that? long/lat in database then measuring distancesbetwee n

> Note quite. Over VERY short distances (<50km or ~30mi) pythagoras is OK,[color=blue]
> but keep in mind LAT/LONG coordinate system is essentially a polar system
> in 3 dimensions (pythagoras is planar in 2 dimensions). Google the whole
> lat/long distance thing. There are plenty of sites showing the mathematics
> to achieve acurate distances between 2 lat/long's - I've seen the raw
> formulae and various implementations from MS-Excell to C/C++ and even PCM![/color]

True. However, if you want the rough distance to the closest hotel etc
then the difference between pythagoras and a spherical solution only
becomes significant when you wouldn't want to go there anyway.

To calculate distances for aeroplane flights I would use a sperical
solution. For nearest hotel it isn't worth the cycles.

[Paul Brooks]

Re: How do they do that? long/lat in database then measuring distances between

On Wed, 25 Feb 2004 09:56:30 +0000, Kevin Thorpe <kevin@pricetra k.com>
wrote:
[color=blue]
>True. However, if you want the rough distance to the closest hotel etc
>then the difference between pythagoras and a spherical solution only
>becomes significant when you wouldn't want to go there anyway.[/color]

Not quite correct. The latitude and longitude scales are in the same
units, but actually use a different scale. This is almost the same at
the equator, but diverges towards the poles. For the UK using
pythagoras would give you a distance approx double the actual value.

Paul Brooks