Website geniuses... can anyone help?

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Posted: Sat Oct 24, 2009 6:03 am

I have another hobby...geocaching. I want to make a puzzle where one goes to a website, puts in a set of latitude/longitude coordinates, then clicks a button. The page then tell the distance in feet to the unknown target coordinates.

This way someone could enter three different coordinates and triangulate to the correct ones, then use trial and error to narrow it to an exact position.

How hard would this be to accomplish, and what type of webspace would be needed to host this (I'm assuming) small program?

I'm clueless about setting this up.

Posted: Sat Oct 24, 2009 11:22 am

I don't know where you're located, but I'm in the Netherlands and have my websites hosted at http://www.antagonist.nl they host my websites (including domain) for €28,something per site per year. That gives me some 2,5 or 3 gig of webspace and 60 gig of datatraffic a month. That's more than any normal website needs (sites like eater obviously need a lot more than that). This should give you a nice indication of what it would cost to host it.

I know a bit (a small bit) about gps-coordinates and you just want the site to tell you the distance from the entered coordinates to the target coordinates? That would be a simple as calculating the difference between both latitudes and both longitudes, apply pythagoras and output the distance? In that case the script would be really simple and the cheapest hosting possible (as long as it offers php-support (or ASP-support, if you can find someone to code in ASP. ASP hosting is less common and AFIK usually a bit more expensive) would suffice.

Anyway, the script is really easy to make, as long as it doesn't require any fancy lay-out it shouldn't take too much time.

EDIT: I suspect that this program only needs to work for one set of target coordinates? If that's the case, and I don't need to add any layout, I'll write you that script as a present for your upcoming eaterversary Wink

Posted: Sat Oct 24, 2009 5:05 pm

Certainly no fancy layout required, but I'm afraid the math is a little more involved than that.

Look at this: http://www.movable-type.co.uk/scripts/latlong-vincenty.html

Of course, I don't need the output to show azimuth or bearing, just distance... and one of the points would be fixed. However, I suspect the math would be the same.

I'll freely admit that this is over my head.

Posted: Sat Oct 24, 2009 5:27 pm

Whether one point is fixed or not doesn't really matter for the math, it does for the scripting a bit.

I believe I've found some premade php-functions that can be used to calculate the distance between two geographical points. If I use those then making this script will only be a matter of making a form and running the input of that form through the found function and outputting that function's result...

The (best looking) code I found was probably using Haversine's formula. From the article you linked to:

Quote:

Vincenty’s formula is accurate to within 0.5mm, or 0.000015″ (!), on the ellipsoid being used. Calculations based on a spherical model, such as the (much simpler) Haversine, are accurate to around 0.3% (which is still good enough for most purposes, of course).

The formula, in php-code, can be found here. Even without any php-knowledge, you might be able to see the math it uses. This function can also output in kilometers, miles and nautical miles.

http://www.zipcodeworld.com/samples/distance.php.html

I don't think we need 0.5 mm precision for geocaching, do we?

EDIT: The page for the Vincenty-formula has a javascript script at the bottom... If that works, I can use that. I know enough javascript to get that working.

Posted: Sat Oct 24, 2009 6:30 pm

I am an out of work land surveyor, so I get what is happening there. I understand the math, but I can't do it.. I have a computer for that Very Happy

This little webpage would need to be up for at least a couple of years. However, it wouldn't see more than 5 visits a week once the initial rush to solve the puzzle passes. At any rate, I don't see more than 50 visits a week for the first month.

Seems to me that that would be a very small amount of traffic, considering that the page would be very simple and the information entered very little. Am I correct in my thinking?

Posted: Sat Oct 24, 2009 11:13 pm

Yes, the amount of data traffic that would generate isn't even worth mentioning.

Posted: Sun Oct 25, 2009 1:44 am

This would not be hard to do at all. Google has an API for their map stuff. It's really easy to use (assuming that you have some programming knowledge).

http://code.google.com/apis/maps/documentation/examples/

Posted: Sun Oct 25, 2009 8:13 am

With that little traffic, there's really no need to pay for hosting as well. There are heaps of free hosts that would be fine for your needs.

ulmb.com comes to mind immediately but there are heaps of others.

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