[worldKit-dev] plotting accuracy

[Mikel Maron]

Hi Iain

Noise is welcome

There's a few things going on here. I'll lay things out in a short story and long story. Both have happy endings.

Short story: 

You've discovered a bug in how the location of input annotations are calculated. I've put in a quick fix, but am going to hold off on releasing it. In the meantime, download worldkit.swf from http://brainoff.com/worldkit/test/accuplot/worldkit.swf. This is version 2.4 20060111-1. Do set , if you are going to display those annotations on the map.

Long story: 

Generally, the way worldKit handles zoom is by scaling and repositioning a layer containing all the annotations (and another layer containing the images). However, Flash internally has a maximum size for any layer. So at a certain magnification, the resolution of plotting becomes coarse.

The option is rather than resizing the datalayer, move those annotations every time the map is zoomed or panned. This is slightly more computationally expensive, so should only be used with necessary. This is set with the unreleased <accuplot> option. (Well, really, I should get some solid statistics on this and then decide to maybe default to this method anyway).

The reason <accuplot> hasn't been released is the problem you discovered with input annotations. The lat/long of the mouse click was determined by the position of the mouse relative to the datalayer. When the datalayer is being resized and repositioned, this works fine, until of course the maximum resolution is hit. With accuplot, the datalayer isn't resized or repositioned, hence the wildly off results.

So actually the problem is how the lat/long of a mouse click is calculated. The worldkit.swf I pointed at calculates the lat/long without relying on the datalayer.

This will go out in the next release. I'd like to release these sort of fixes immediately, but I still haven't set a communal code repository yet.

Best, Mikel

----- Original Message ----
From: Iain Mott <mott at reverberant.com>
To: worldkit-dev at lists.brainoff.com
Sent: Wednesday, January 11, 2006 1:13:34 AM
Subject: [worldKit-dev] plotting accuracy

Hello

I'll continue to be noisy on this list for a little more...

I've making a page that allows users to upload/plot files onto a WMS map
as well as annotations. Have based the plotting mechanism on the
javascript example at http://brainoff.com/worldkit/geocoder. The page is
working, however at high magnifications the plotting resolution proves
coarse and inaccurate.

I've seen an undocumented tag <accuplot> in one of mikel's config files.
Thinking this might be an answer i tried setting it to true, but
unfortunately it sends the plotting (the lat and long values generated
by the mouse click) right out of whack.

googling for accuplot i see that there may be some problems with it.

Is the problem I'm having something that's yet to be resolved in
worldkit or am I doing something wrong?

My messy config file is at:
http://www.reverberant.com/ct/annotwk/config.xml (if your browser
refuses to view it try:
http://www.reverberant.com/ct/annotwk/config.txt)

cheers,

Iain


-- 
Iain Mott
www.reverberant.com

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