CS 128/ES Lecture 9a1 Geocoding and Routing Ya can’t get thereah from hereah!

CS 128/ES Lecture 9a2 The Traveling Salesman Problem (TSP) A Salesman must visit each of N cities and return to his home base, driving as few miles as possible Insert Joke Here

CS 128/ES Lecture 9a3 Difficulty of TSP Of interest to theoretical computer scientists because The Problem Is HARD So hard that if you could compute an exact solution efficiently, you could also disrupt the world’s financial markets

CS 128/ES Lecture 9a4 Applications of TSP Inspection routes Traveling Salespersons Delivery professionals

CS 128/ES Lecture 9a5 Knowing Where You Are GEOCODING “is the process of converting an address into a point location.” McDonnell and Kemp, International GIS Dictionary, 2 nd Ed., 1998 “Hey, hey, hey. Don't be mean. We don't have to be mean because, remember, no matter where you go, there you are.” Buckaroo Banzai (from The Adventures of Buckaroo Banzai Across the Eighth Dimension)

CS 128/ES Lecture 9a6 TIGER Maps – The Key to Routing TIGER maps are the primary data set used for geocoding. … and geocoding is the basis for all routing.

CS 128/ES Lecture 9a7 TIGER Map of the Area Dr. Levine’s House

CS 128/ES Lecture 9a8 TIGER Attribute Data

CS 128/ES Lecture 9a9 Some Useful Fields FIDField ID Number LENGTHLength of full extent FNODEIntersection of “start” of street TNODEIntersection of “end” of street FENAMEStreet name (root) FRADDR# of first house on RIGHT side TOADDL# of last house on LEFT side ZIPRZip code of RIGHT side

CS 128/ES Lecture 9a10 How to Find an Address 1.Find the records for the appropriate street. (There may be more than one.) 2.Find the particular record whose address range includes your house number. 3.Decide “left” or “right” based on parity. 4.Interpolate. 23

CS 128/ES Lecture 9a11 But Apply Georgian’s First Law Don’t process the data yourself; get someone else to do it (of data processing)

CS 128/ES Lecture 9a12 Limitations of Geocoding Mapquest says Dr. Georgian lives here Dr. Georgian says he lives here Whom do you believe?

CS 128/ES Lecture 9a13 Why Is It Wrong? FRADDR3179 TOADDR3297 FRADDL0 TOADDL0 Where is Dr. Levine’s House? (#3299)

CS 128/ES Lecture 9a14 A Common TIGER Error  TIGER Files commonly miscode the F… and T… fields.  This results in various “mirroring” errors.  Newer versions of the data make this error less frequently.  Both Dr. Georgian and Dr. Levine are “victims” of this kind of error.

CS 128/ES Lecture 9a15 Other TIGER Errors This road does not exist! Data Lag causes errors as new roads are (or are not) built

CS 128/ES Lecture 9a16 How Do We “Really” Do It? By following instructions in tomorrow’s lab!

CS 128/ES Lecture 9a17 Going “Big” Time One can easily geocode many addresses at once. Place them all in a table and then ask the system to do so. This gives you all of your “hot” locations.

CS 128/ES Lecture 9a18 Now, How Do You Visit Them All?

CS 128/ES Lecture 9a19 How many ways are there? For 20 stops, there are 20x19x18x…x3x2x1 = 2,432,902,008,176,640,000 Possible routes! (that’s 2 quintillion) Once again, we cannot be exact Once again, we need a GIS

CS 128/ES Lecture 9a20 A Simple (non-)Solution Choose the route yourself It turns out that humans, particularly experienced humans, are good at this Then check only your 3 (or 40) best guesses!

CS 128/ES Lecture 9a21 Working with Simpler Routes So it can be done And we can’t do it

CS 128/ES Lecture 9a22 A Poor Man’s Solution 1.Select the lines that comprise your route. 2.Create a layer out of the selection. 3.Create a query that sums the lengths of the roads.

CS 128/ES Lecture 9a23 Conclusions Finding, Creating, and Measuring routes is a key task of many GIS’s. With ArcMap, we can do this for Points (geocoding), but not for extended routes. There are some “workarounds” we can use. ?