RE: [MI-L] How mapinfo loads map data

Mon, 05 Jun 2006 03:29:06 -0700

Title: Message
Hello Tim,
 
The ability to dynamically load only the parts of a map layer that are in a current view is achieved through a spatial index. This avoids the need for any map renderer to go through all features to test if they are needed for the view. MapInfo uses a spatial indexing method known as R-Tree. Since I'm not too familiar with MITAB, I don't know if it has the ability to use this index to query features in a table based on a coordinate rectangle. It would not surprise me if it didn't since I believe MITAB was originally written for external (i.e. outside a MapInfo environment) read/write of TAB file sets, and maybe not with a home-brew renderer in mind.
 
Regards,
Warren Vick
Europa Technologies Ltd.
http://www.europa-tech.com
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Tim Smith
Sent: 05 June 2006 10:07
To: <MapInfo-L
Subject: [MI-L] How mapinfo loads map data

 
Hi,
 
I'm creating my own map renderer - much like MapX ,  using mitab.
 
The question I have is regarding how mapinfo handles displaying large datasets. I guess it dynamically loads only what it needs to display, but how is this done? How does mapinfo know which features to load based on the area that you are trying to look at?
 
More specifically, has anyone tried creating a map renderer, and have they (possibly with mitab) tried this before?
 
Any level of help with this would be appreciated.
 
Kind regards
 
Tim
 
(I'll ask specific mitab questions on its mailing list)
 
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