Hello
I'm rather new to Sketchup (been learning for projects at home since Sept 07 and had sketchup pro 6 at work for about a month), more enthusiasm that knowledge sadly, so I'll apologise now if these issues are a bit obvious!
I'm trying to combine the accuracy and precise content of GIS with the accessibility of images in sketchup to create visualisations to be used in a flood alleviation scheme. It's important that the terrain models are as accurate as possible just in case the decisions subsequently made are examined at a later date.
With that in mind I've requested height/elevation data for the whole geographic area that we are looking at and tried to convert it in GIS so that I can use it through the sketchup plugin.
The only data I could get hold of was lidar ascii files. I went through quite a long winded procedure creating a polygon grid as a shapefile (pinpointing xy positions) and extracting z coordinates from the lidar data, joining the two files together which resulted in a shapefile which I could transform into a 'feature class'. I did the same for the buildings using an OS polygon shapefile from which I created point data at the centre of each building and then extracting the z coordinates as before and ultimately created a building feature class.
At this point I should admit that at all points I've been feeling my way forward, my knowledge of GIS had previously been limited to the management and creation of geodatabases which I could use to create reports on features within geographical ares (specifically for me the illustration/reporting of ecological features and the recording of the quality/condition of a site with photos and notes). I haven't had formal training just learnt as I've gone along so there are huge gaps in my knowledge.
When I processed the information through the sketchup plugin I extruded the building feature class - this worked really well 
However, when I asked it to 'elevate' the terrain feature class - this resulted in lots of individually grouped tiles (elevated to the correct height!) - now this looks very interesting, but isn't the 'one-piece' terrain which I had hoped for.
Can anyone help please, I'm feeling around in the dark! Am I using the correct data? Am I treating it in the right way? What's a 'tin'? Where could I get the right data from? What questions should I be asking?
Thank you so much
Clemantine