### Makefile --- Indianola, Iowa address grid
## Author: Dan Jacobson https://www.jidanni.org/
## Copyright: https://www.gnu.org/licenses/gpl.html
## Created: 2025-01-18T07:37:16+0000
## Last-Updated: 2025-01-18T08:28:40+0000
##     Update #: 8
## https://www.openstreetmap.org/user/b-unicycling/diary/405898#comment58665

## Is Indianola's house addressing system officially described
## anywhere? We observe it is centered at Howard St. and Salem Av. but
## (100 N/S/E/W). We also observe 3rd Av. begins the 400 S. block, 4th
## Av. begins the 500 S. block... "E" St. begins the 500 W. block, "F"
## St. begins the 600 W. block... but 20th St. begins the 2000 E.
## block...

## So for our ground control
## points, we will first subtract 100, then post process later.
## We will start with just three observations, gained via
## Overpass turbo query {{geocodeArea:indianola iowa}}->.a;
## nw["addr:housenumber"~"."](area.a); out geom;
## We also check the county GIS. 
## 
GCPs = \
0 0 -93.56098 41.36022 \
200 2100 -93.55874 41.38384 ...