HELP merge

[Scott Tweddale]

I have used GRASS to merge a 20m multispectral scene of Spearfish,SD with
a 10m panchromatic scene.  An overview of this process is included in the
Fall 1989 issue of Grassclippings.  Basically, I used a 4 step process.

1. Georeference your lower resolution bands to your higher resolution bands
using i.points and i.rectify

2. Set your resolution (g.region) to be equal to the resolution of your 
highest resolution bands.  Add and subtract different combinations of the
georeferenced multispectral and panchromatic bands.  In my example, I added
and subtracted the 10m panchromatic band to each of the three 20m MS bands,
resulting in a total of 6 new bands.

3. Preview different combinations of your newly created bands using i.colors.
Once an optimal band and color combination is determined, use i.composite to
create a color composite image containing complimentary spatial information
from your higher resolution data and spectral information from your 
multispectral data.

I guess that was a 3 step process, not 4.  Also, a good reference article:

Digital Merging of LandsatTM and Digitized NHAP Data for 1:24,000 Scale Image
Mapping
Photogrammetric Engineering and Remote Sensing, Vol. 52, Oct. 1986,
pp. 1637-1646

Pat S. Chavez, Jr.- USGS

This article includes a good discussion of other digital merging techniques,
including band ratios and the use of pricipal components analysis.


Scott Tweddale
U. of Illinois GIS Lab/USA-CERL