1. Data compression Why compress (or ‘zip’)? Lossy vs. lossless
For image archiving (satellite data)
For image transfer over internet
Lossy vs. lossless
.jpeg is ‘lossy’ (some info. lost)
.tiff is ‘lossless’ (no info. lost)

2. Data compression
281 kb
673 kb

3. Data compression
6.86 MB
15.2 MB

4. Data compression
6.2 MB
1.6 MB

5. Data compression
Run-length codes
Ex. # 1
Ex. # 2

6. Data compression Quadtree
A quadtree recursively subdivides a plane into 4 quadrants
If area is homogeneous, subdividing stops
If the quadrant is heterogeneous with respect to this attribute, further subdivision occurs
And so on, and so on, until…..

7. Data compression
Quadtree

8. Data compression
Quadtree
256 pixels down to to 80

9. Data compression Quadtree
2304 vs. 160 (or so); run on polygon, not line

12. Lab Four
GOAL:
Make your .jpg of campus a georeferenced map layer that you can use in GIS software.
Use your waypoints to NAIL the known coordinates to specific places on campus.
Order: map, waypoint; map, waypoint;…
INDEPENDENT WORK:
Your group uses same Excel file