Irricad

Hi John,

Converting lats/longs to planar coords can be a tricky business and can depend on the projection type you want/have to use, and where the reference point is for your area of the world. However, if you are using Google Earth I'd suggest using the Universal Transverse Mercator (UTM) system - because that is built in!

In Google Earth look under Tools|Options... Show Lat/Long - you can select UTM there, and the lats and longs will be 'planarised' to the correct UTM zone.

For instance, our office is at 43°38'43.89" S 172°28'03.43" E or UTM Zone 59 618364.64m E 5166481.03m S. If you use these coords you can swap between Irricad and the 'real world' with ease. If you do use them though, I'd suggest making use of Irricad's grid user origin capability (Settings|Grid/Origin) to make the numbers more managable.

You can find out more about UTM here:
http://en.wikipedia.org/wiki/Universal_ ... ate_system

Hope this helps,

Dan

Hi Jimmy,

Google Earth does have elevations, but they are difficult to extract directly from there. There are based on SRTM data and probably won't be accurate enough for your purposes.

You can also get elevation data from USGS, which is more accurate than the STRM dataset. This still may not be good enough depending on the relative accuracy (more important than absolute accuracy) at the location you are interested in. For instance, you can get USGS derived elevations for Washington State here:

http://gis.ess.washington.edu/data/rast ... index.html

Failing the above, you would have to rely on local surveys - which would more than likely end up in AutoCAD format, or buy data from a company such as Intermap. The Intermap dataset is very new and very accurate, but obviously, it comes at a cost.

Hope this helps,

Dan