Integrating Multiple Data Sources

• one of the biggest problems in building a 3D world from data sources is alignment - different data sources have different degrees of accuracy, projection conventions, etc. which makes them not line up
• it can be very difficult and time consuming to compare each of your data sources against each other, to judge which source is responsible for the discrepancy, and which is closer to the real world
• ideally, you would use a single application to quickly check any sort of spatial data against another, but that application doesn't exist
• satellite/aerial imagery can be the most difficult to align properly, though it's a little easier if it comes in GeoTIFF format
• various solutions for comparing data, presuming that one doesn't have any expensive software:

vs.	DEM	LULC	GeoTIFF imagery
DLG	use Global Mapper or VTBuilder	use VTBuilder or Maptitude	use Global Mapper
DEM	X	use VTBuilder	no solution
LULC		X	use Maptitude

• since it's difficult to compare imagery directly to DEM, it might help to take two steps:
  • first, compare the DEM to the DLG using Global Mapper, make sure they're lined up well
  • second, compare the DLG lines to the imagery - there's no standard program to do this; i had to write my own, ask me if you need help

• comparing elevation to vector data
  • try to load patches along a coastline
  • it's very difficult to tell if the data lines up unless you have a shoreline or other obvious geographic feature that can be visually compared

• high-end packages
  • ENVI
    • may work well for comparing DEM, DLG, and GeoTIFF
    • no LULC support
    • too expensive (> $4000)