1	Spatial Data Development Using ArcGIS Geog378 CCSU - Geography
2	Career Ladder Technician Accomplished defined tasks Data input and mapped output Data management Analyst Define tasks for technicians Analysis Manager Projects Proposals Budgets workflow People Technicians and analysts
3	P.R.O.D. Prepare Get maps ready for digitizing Register Tie to real-world coordinate system Options Snapping and other options Digitize Heads up Heads down
4	Prepare Heads down digitizing Locating control points (4 plus) Keeping flat Heads up digitizing Scanning Locating control points Color or black and white? Resolution Keeping flat
5	Register Affine transformation Real World Coordinates x/y = f(digitizer/scanner x/y) Uses Ordinary Least Squares Accounts for Rotation Scale change Plane to plane transformation
6	Register, cont. Root Mean Square Error (RMSE) Distance from predicted (equations) to actual squared Summed over all control points Square root of the sum is taken A measure of how close you have come – should be within the error of the data
7	Options Snapping Snap to other layers Vertex, end or edge End only with lines Points don’t usually snap Snap to edit sketch Options Whole bunches of them Most important – snapping tolerance and sticky move tolerance These can be changed during digitizing
8	Digitize Custom toolbars Customize the drop down menu Comfort Music Good mouse Good chair Pace Only real pros can do more than 2 hours in a stretch
9	Heads Down vs. Heads Up Heads Up – scanned maps registered to real world coordinate system Done on the screen Most common form today Scanner services widely available Heads Down – paper maps mounted on digitizing tablet Not used much now Possibly for maps too fragile to put through a scanner
10	Acronym Review Prepare Register Options Digitize
11	New Stuff that Doesn’t Fit the Acronym Geodatabase Topology Spatial data validation Rules based No gaps between polygons Polygons from this layer shall not overlap polygons from that layer Points from this layer must be inside polygons from this layer Allows you to locate and fix errors Or mark as exception
12	Digitizing Issues Slivers – small, narrow polygons (usually errors) Dangles – vertices that hang out there Gores – gaps between polygons Undershoots – lines that do not quite touch other lines Overshoots – lines that extend beyond other lines