Raster
data and coordinate systems
Like vector data, raster
datasets are not very useful unless they are registered (aligned) to one
another through a common coordinate system. Before you can perform even basic
operations like merging or overlaying, you need to tie the raster dataset to
the landscape. ArcGIS offers two methods for changing
various parameters of your data's coordinate system, including the map
projection.
On-the-fly coordinate
system change
ArcGIS Spatial Analyst can combine multiple rasters in different projections (coordinate systems) and
output the result in yet another projection by performing a “fast”
projection-on-the-fly. You may specify the projection that should be used to
create the output raster as one of the analysis properties set in the Options
dialog. Projection-on-the-fly won’t work for rasters
that have no projection information stored with them.
Permanent coordinate
system change
ArcToolbox provides tools for permanently changing
the map projection and other coordinate system parameters for a source dataset.
For example, if you receive a dataset that doesn't match the map projection of
your database, you can use the ArcToolbox Project
Wizard to change the new dataset's map projection to match your database.