JBOX - distance measuring

[Charlton Purvis]

Hi, folks:

I just posted this to the maptools bugzilla in response to an open
javascript distance measuring tool that may hopefully end up in ka-map.

If you look at the bottom post on
http://bugzilla.maptools.org/show_bug.cgi?id=1145, there is a demo page that
demonstrates a simple JS distance measuring application.  I can't take
credit for the JS -- I just found it.

It works fine for me.

Charlton

> -----Original Message-----
> From: UMN MapServer Users List [mailto:MAPSERVER-USERS at LISTS.UMN.EDU] On
> Behalf Of Richard Greenwood
> Sent: Wednesday, December 28, 2005 9:50 AM
> To: MAPSERVER-USERS at LISTS.UMN.EDU
> Subject: Re: [UMN_MAPSERVER-USERS] JBOX - distance measuring
> 
> salah jubeh <s_jubeh <at> YAHOO.COM> writes:
> 
> >
> >
> > Hi Guys     I want to know how this function works - what are these
> parameters
> s, t, and specially c.     also is there is any way to do this without
> applets.
> since the client has to download java VM and many times compatibility
> problems
> occurs.     Thanks in advance.     function measure_handler(name, s, t, n,
> a)
> {// c = 1 / 72dpi / 12inches_per_foot * 1.0003state_plane_scale_factorvar
> c =
> 0.0011577546296296; // constantvar f = [scale] * c; // scale factorif
> ((s>0) ||
> (t>0)) {defaultStatus = "This segment = " + s*f + ", Total = " + t*f + ",
> Number
> of vertices = " + n ;}}
> 
> 
> jBox returns values in screen pixels.
>     function measure_handler(name, s, t, n, a)
> s is the length of the current segment (in pixels)
> t is the total length of all segments
> n is the total number of verices (pionts clicked)
> a is the area in screen pixels
> 
> You must convert the pixel values to real world values with javascript
> code.
> Basically pixel_value * conversion_factor = real_world_distance. The
> conversin_factor is the size of the screen pixel in real world units. The
> 'c' in
> the example is a constant used in that caluclation.
> 
> HTH,
> Richard Greenwood