Plotting map locations on a web page

**xoggoth** · 31 January 2005, 22:45

If the towns can be shown as reasonably simple shapes like circles or polygons etc. I suggest you take a look at Walter Zorn's freeware dhtml graphics package as he has done all the hard stuff for you. This is excellent.

www.walterzorn.com

If you want more complicated irregular areas that's a bit more difficult but possible using transparent gif images inside divs on a background map. Make them invisible and then change to visible when clicked on. You can also highlight areas using the jscript filters property.

If you want some code examples I could bing a few on my webtulipe if you email me.

**fiddleabout** · 1 February 2005, 10:02

Ooops - just realised you want multiple pins - my quick'n'dirty was for a single pin by using MultiMap

**WxMan** · 1 February 2005, 11:08

Thanks for the reply Frank – Really this should be easy if I can just find the right direction to be pointed in..

A sample map can be found here
www.torro.org.uk/archive/ukmap.htm

And the data set can be found here
www.torro.org.uk/archive/

So.. given the following data that I could query out of the database I.E.

Event&nbsp &nbsp &nbsp &nbsp LAT&nbsp &nbsp &nbsp &nbsp LON
WS&nbsp &nbsp &nbsp &nbsp 56.164&nbsp &nbsp &nbsp &nbsp -2.550
TN&nbsp &nbsp &nbsp &nbsp 53.092&nbsp &nbsp &nbsp &nbsp -2.303
TN&nbsp &nbsp &nbsp &nbsp 52.719&nbsp &nbsp &nbsp &nbsp -1.765
TN&nbsp &nbsp &nbsp &nbsp 54.483&nbsp &nbsp &nbsp &nbsp -7.133
TN&nbsp &nbsp &nbsp &nbsp 53.092&nbsp &nbsp &nbsp &nbsp -2.302

I would want to place a symbol for a WS at 56.164 and -2.550 etc. A different query would return another set of values and hence different locations plotted on the map. The map image would always remain the same.

I wonder if I were to some how convert the LAT LON values to pixels I could just use the old HTML MAP and put a blob on the map at the pixel location?

Again any other suggestion would be really welcome at this stage.

**ScotsPine** · 1 February 2005, 11:42

hmmm,

convert the LAT LON values to pixels - do that and then use dhtml to create a layer with your symbols (as gifs) positioned on it. should be pretty straightforward(?)

**WxMan** · 1 February 2005, 13:36

Re: hmmm,

I will certainly look at a conversion to pixels but one thought is that the 0,0 pixel is in the top right corner - sadly this does not tie in well with LOG / LAT as it would need to have it in the lower Right corner – so there would have to be some horrendous conversion going on there in order to convert it and I am not sure that I could do this … perhaps if I invert the LOG LAT values it might work…

Any way thanks to fiddle’s tip/hint I managed to add multimap to my LOG /LAT finder tool. I am not actually a ASP programmer so I am using this a learning curve… which really means don’t over criticise my basic pages

www.torro.org.uk/misc/lon...on-lat.asp

**fiddleabout** · 1 February 2005, 15:29

Re: hmmm,

Multimap is very good - I started using it on my campsite finder website (kwikbreaks) more or less when I first created it - within six months all the other buggers had copied me

**xoggoth** · 1 February 2005, 22:32

Re: hmmm,

Why on earth is conversion to pixels difficult? That's basic O level mafs that applies to any scaling prob regardless of what increases in which direction and what the origins are, viz:

ypixels = ypixelsbottom + (ylat-ylatbottom) * (ypixelstop - ypixelsbottom) / (ylattop-ylatbottom)

Or have I misunderstood the question again?

**WxMan** · 2 February 2005, 01:24

Re: hmmm,

Frank you have really helped my out here

as that formula was just the conversion that I needed. Now that I can convert LAT LON to pixels the rest should be easy - I will report back tomorrow some time with the first draft of the page

BTW here is the formulafor the LON conversion.

xpixels = Round(xpixelsleft + (xlon-xlatleft) * (xpixelsright - xpixelsleft) / (xlatright-xlatleft),0)

Are you sure this was o-level ?? I dont recall it all

**WxMan** · 2 February 2005, 01:34

Re: hmmm,

Right off now to swot up on DHTML layers - somthing else that I have not delt with before

Plotting map locations on a web page