For Upper Flood I have been starting from a PDF with UKOS 100m grid ex Therion, converting it to a two colour White/Transparent and Magenta png and then using the free MS Mapcruncher (see my bit on the www.mapki.com on how to load Mapcruncher tiles into Google Maps). For Swildons etc, I simply scanned pages from Mendip Underground (I have asked Tony Jarratt!). Mapcruncher does a fair job at anti-aliased resizing. You can edit Mapcruncher's XML project file by hand to use known survey - WGS84 Lat/Lon correspondences.
Ideally, for raster layers, the cave would be re-rendered with a decent line width and text size at different zoom levels, hence my suggestion for including the raster rendering into Therion. Also when showing a large map area with a raster cave overlay, some way of merging cave data from multiple source surveys onto a single Google overlay tile is needed. A server based solution would be nifty. Surveyors could simply post their georefed survey (GeoTif/PDF/KML) and it would appear on a Google Maps or MS Virtual Earth website. It should not be too much trouble to generate the web page code automatically. Google Maps and MS VE use the same simple spherical Mercator projection. Google Maps can display a KML file as an overlay (2Mbyte limit I think). I guess rendering cave overlays from KML might solve some the linewidth scaling and the survey merging problem of the raster solution. Does anyone have an online example ? Landowner / access controller sensitivities must be respected on any public website. For my Mendips page, I worked with the UK CSCC. We have a 'no location without access information' rule. Bill Chadwick -----Original Message----- From: Julian Todd [mailto:[email protected]] Sent: 28 January 2007 18:45 To: therion at speleo.sk Subject: Re: [Therion] Cave Overlays on Google Maps Web Sites Martin Sluka wrote: > On 27.1.2007, at 22:09, Bill Chadwick wrote: > > >> It is quite easy to create a web page that shows a cave survey >> overlay on >> top of Google / Virtual Earth maps. >> > > Good work! > > There is only one problem - google doesn't calculate with underground > in 3D - so you may not see the vertical dependencies, the caves are > always on surface. > > Martin > It looks like simultaneous invention all round. I'm doing something on this too. I think it should work for any paper survey that you can scan and upload, not just computerized ones output from therion or tunnel. I have a server which can do tile cutting of a large bitmap of a cave survey. It's going to be important to create a mask of transparencies so you can see it overlayed without all the whitespace outside of the cave passage. Julian T.
