Wednesday, February 28, 2007

No Doughnuts

Tonight Pete revealed something to us. Something disturbing. There can be no doughnuts. Fortunately, it is not as bad as it sounds. He was referring to polygons in the older ARC coverage files. A doughnut in this sense of the word is when you have a polygon object, but there is an area inside that polygon that has different attributes. For example, a city may have an area within it's larger boundaries that is not incorporated by the city. That is the hole in the doughnut. The coverage files apparently had a lot of trouble with these. The later shapefiles and geodatabases are totally cool with doughnuts though.

Over there on the right is an example of some of our exercising tonight. It was about association tables to each other and to spatial data. Pete had a good example of a desire to make a campus map showing which buildings were served by which security guards. In this example, there was some map data of the campus, and the chief of security guards also had a spreadsheet with a list of his officers and which buildings they covered. So then we related those 2 datafiles and were able to automatically generate the map showing the buildings and the names of the security guards for each and even color coded them by security officer.

Wednesday, February 14, 2007

Romance is in the Air

There's the map of counties in the United States which lost population in the period from 1990 to 2000, and who also had more male than female residents. We studied queries in this chapter and it was really getting into the analysis power of GIS. It was interesting, and I was impressed at all the possibilities for analyzing spatial data with SQL statements. Mary didn't find it so interesting, but maybe if she were working on a more real life scenario, she would like it better. I also determined that Mary did not contribute to the lost population trend seen in the map to the right. All the talk about queries reminded me of a fellow student in a previous database class who pronounced that word more like "quiries" with a long "I" sound in the first part of the word.

Since it was valentines day, it was a special day at GIS class. There was an air of electricity and anticipation as we all worked on our projects. The boys and girls exchanged long looks and sideways glances. Some couldn't help themselves and burst into singing romantic songs.

It was also a special day because it was on this day in 1989 that the first GIS satellite was launched. That doesn't seem that long ago when I think about the fact that I have a GPS in my car and almost take it for granted as a navigation aid. I also remember the time of the launch and thinking that GPS sounded so exotic that regular people like me would probably never get to use it.

Saturday, February 10, 2007

Lost in Translation

for clicking the image if you better and larger to see it. your hands will be free moving.

Wednesday, February 7, 2007

It's Time for Tables

We had our first test tonight. I thought it was a very fair assessment of the material we had covered. I know I got some things wrong, I hope not too many.

Tonight we worked with tables. It was a lot of fun. Well, not really. It took me back to database classes I had in the past, and was a good refresher on db concepts and how ArcGIS uses tables. The exercises got intense with linking and relating tables, and talk of cardinality. I remember those relationships in MS Access and how they could get pretty messed up. Good thing relationships in real life don't get messed up like that. But then, in computer databases you can usually click yourself around and straighten things out. I made this map, which didn't export very nicely, about how many federal elected officials each state has. Later we did some more advanced data manipulation in the tables that was impressive, but yielded no spatial data output vectors to sho on here.

Sunday, February 4, 2007

Air Conditioner: The Final Chapter

It is out of the bedroom!
It has gone to the basement
to be with friends.
Other air conditioners
in my collection.