Tracking map window history could greatly improve the ability to navigate maps. This feature should save zoom, theme, tool and position at every change of map status, and allow the user to go back to previous views.
The aim is to link different projects, possibly concerning the same area at very different scales. For example, a single project could represent a whole conuntry, and could be linked to different projects representing single regions, possibly located on different servers.
This could be accomplished deriving a new TMap object in which there is a layers() array of tiles instead of a single tiles layer. Transparency can be obtained exporting maps with a choosen background color and converting the files with appropriate filters.
Transparent map overlaying would allow the uses to freely combine map layers, without having the need to export every layer combination from the GIS system; this would thus give the user the ability to customize the map layout.
One possible implementation could be saving the imagemaps as array assignment instructions: this would allow to load each imagemap file separately, and then write the whole imagemap:
Non-matched tilesets have tiles that do not overlay exactly, due to different tile dimensions or different tileset origins. This implies the use of different TFrame objects for each layer, all with a common clipping area.
Instead of loading exact tiles as in a chessboard, the map window should load a block of tiles, center it on the required point and clip the view.
Intermediate zooming between fixed levels could be accomplished by changing the tile image height and width properties, thus relying on the browser's ability to rescale images according to gives sizes. Probably not a great improvement, if we consider how bad raster images look after rescaling.
A support for JS-GIS browser pages not using frames would need cookies to make things work. Instead of mantaining the map status in global variables in the main frameset, the status should be saved in a cookie and reloaded every time the map page is updated.
The library should be tested with all JS-enabled browsers on the major platforms. At present. it doesn't work with Netscape 4.0/4.7.
The support for handheld computers should cover the problems related with small displays, for example map scrolling.
JS-GIS © 2001, 2002 by Luca S. Percich (mailto:email@example.com)
Last updated: dec 26, 2002