Lecture 7 Digitizing. Dr. Zhang Spring, 2017

Transcription

1 Lecture 7 Digitizing Dr. Zhang Spring, 2017

2 Model of the course Using and making maps Navigating GIS maps Map design Working with spatial data Geoprocessing Spatial data infrastructure Digitizing File geodatabases Geocoding Interactive maps Map Animations Map layouts Spatial analysis 3D GIS Proximity analysis Raster analysis Analyzing Spatial data Network analysis Data mining Spatial regression

3 Outline Digitizing overview GIS features Digitizing features in ArcMap Advanced digitizing tools Transforms and spatial adjustments 3

4 Lecture 7 DIGITIZING OVERVIEW 4

5 Why digitize? New maps Map features are wrong Missing features Other? 5

6 Heads down digitizing Digitizing tablets Used to digitize hard copy maps into GIS Transform wire intersections into coordinates of the tablet s coordinate system

7 Steps for heads down digitizing Tape map to the digitizing tablet Register control points on the map Control points Puck Estimate two conversion equations (one for vertical and one for horizontal coordinates) Tape Digitize vectors (points, lines, or polygons) Map 7

8 Heads up digitizing Mouse on a screen Digitizes paper maps, aerial photos, or other images 8

9 Lecture 7 GIS FEATURES 9

10 Points Single features Nodes Line endpoints Vertex points Controls shapes of lines and polygons 10

11 Creating points Heads up digitizing Single point features Sketch tool and snapping features Points added as XY event files (chapter 4) Points added using geocoding functions (chapter 8) 11

12 Lines Starting and ending points with shape vertex points as needed Vertex points 12

13 Line attributes Shape From and To attributes Node Address (street centerlines) Lat/long Length 13

14 Polygons Three or more lines joined to form a closed area Single polygons or multipart features Hawaiian islands can be multiple polygons as one feature 14

15 Polygon attributes Shape Area Perimeter Length 15

16 Constructions tools Points Lines Polygons 16

17 Lecture 7 DIGITIZING FEATURES IN ARCMAP 17

18 Create new feature class In Catalog Navigate to desired location Create new feature class or shapefile Add spatial reference information Add new fields (optional) 18

19 Digitize new features In ArcMap Create base map Add feature class Start editing Digitize feature Stop editing and save 19

20 Create base map Vector features or raster images Add features 20

21 Start editing Start editing 21

22 Begin digitizing pick points 22

23 Stop editing Editor toolbar, Stop editing Save edits 23

24 Edit attribute data Start editing, populate fields in table (create fields if necessary) 24

25 Lecture 7 ADVANCED DIGITIZING TOOLS 25

26 Specify angle and length Lines and polygons Straight segment tool Type length and angle 26

27 Snapping tools Snapping toolbar 27

28 Trace tool Good for complicated shapes Editor toolbar,trace tool 28

29 Generalize tool Creates features for use at small scales with less detail while preserving basic shapes US Census cartographic boundary files Census TIGER water features Generalized/Small scale Modified rivers Smoothed/Large scale 29

30 Smooth tool Smoothes sharp angles in polygon outlines to improve aesthetic or cartographic quality Smooth before Smooth after 30

31 Cut polygons Creates two polygons from one original Cut polygon tool Polygon before Polygon after 31

32 Move and rotate Adjusts features Polygon before Polygon after 32

33 Lecture 7 TRANSFORMS AND SPATIAL ADJUSTMENTS 33

34 Transforms Converts data From one coordinate system to another. From digitizer or scanner units to real world coordinates. Shifts data Within a coordinate system, (for example, feet to meters). 34

35 Rubbersheeting Geometric distortions commonly occur in source maps May be introduced by imperfect registration in map compilation Lack of geodetic control in source data Variety of other causes Corrects flaws through the geometric adjustment of coordinates 35

36 Edgematching Aligns features along the edge of one layer to features of an adjoining layer Layer with the less accurate features is adjusted, while the adjoining layer is used as the control. Attribute transfer is typically used to copy attributes from a less accurate layer to a more accurate one. 36

37 Spatial adjustment example CAD drawings (buildings) Generally do not have geographic coordinates Hamburg Hall CAD drawing Hamburg Hall Ortho photo 37

38 Spatial adjustment example Spatially match drawing to map using displacement links 38

39 Summary Digitizing overview GIS features Digitizing features in ArcMap Advanced digitizing tools Transforms and spatial adjustments 39

40 Lab Tutorial 7-1 (p256) Tutorial 7-5 (p279) 40