Editing and Analysis

Notes on Editing We have covered feature editing But not table editing

Creating New FC Biggest problem is remembering that the EDIT button is where you set the spatial reference for new empty FCs.

New, empty FC table When creating a new field in a table –If you are using float or Double real numbers then you have to specify Precision and Scale. Precision = number of digits Scale is number of decimals has P=5 and S=2 As I said before, this is actually a complex subject if you want to dig into it see on-line help.

Tables can be edited… While in edit mode And While not in edit mode But the behavior is different And this can be a major pain because sometimes you have to keep switching back and forth!

Some Table Option functions FUNCTIONEdit mode NOTEDIT MODE Select by attributeXX Clear selectionX Switch selectionXX Select AllXX Add fieldX Add table to layoutXX Print tableXX Export tableXX Format tableXX Default table fields (min width)XX

Field Operations Rt click on column head and you get And a warning if you are not in Edit mode So? Summarize - table Stats – table & graphic Turn field off – where do you turn it back on?

Booby traps If you calculate fields the calculation will only be done for selected rows IF any rows are selected. There is a check box that controls this but usually you want this behavior

Analysis Starts with selection… Why? Because –Many steps in analysis are simply selection by Attribute Location –Most of the OVERLAY functions’ operations depend on what features are selected

Booby Traps Selection is full of booby traps Most due to careless implementation –Wrong files (dialog remembers) –Wrong operation in Select by Location –Building complex operations in either query Too many ANDs and Ors – logic not arithmetic Messing up AND and OR – too complex –The Intersect function in Select by location does not give the same results as Intersect in Overlay Analysis

–Building complex operations in either query Too many ANDs and ORs – logic not arithmetic Messing up AND and OR – too complex –a AND (b OR c)  (a AND b) OR c –a AND (b OR c) =(a AND b) OR (a AND c) –Beginners – carry out each operation separately and study results! –This means you build up a bunch of layers so you have to name them carefully! –And you have to pay attention to what you are selection from!

Booby Trap Select by location using Intersect does not give the same results as Overlay Intersect

Overlay Intersection BUT THE RESULT IS VERY DIFFERENT! Red outlines are the parcels selected by Select by Location Intersection Green are the result of the Intersection Overlay