Objectives. Cartographic Data Capture. Concepts, and Hardware, Review Review of data needed to make a map. Overview. Information needed to make a map

Transcription

1 Objectives Cartographic Data Capture Concepts, and Hardware, Provide Provide an overview of the basic tasks of data capture: conversion of graphic information that appears as points, lines, and areas on maps... into into digital form to be stored and manipulated within the computer. 1 Overview Review Review of data needed to make a map Steps Steps in data collection process Two Two fundamental approaches: raster & vector Vector Vector mode data capture Raster Raster mode data capture Information needed to make a map Base map for extracting cartographic data: Projection information Location Location of control points Location Location of all cartographic features to capture [points, lines, areas] Attribute data values for: PointsPoints LinesLines AreasAreas LabelsLabels

2 Steps in procedure for automated capture of base map Acquisition of stable, geo-referenced base map materials drawn at a scale appropriate to the mapping project Initial data capture: : a device is needed that enables conversion of the graphic image on the map into digital form [hardware dependent and intensive] Editing of captured data for generalization, simplification, and error correction Manipulation and transformation of the captured, corrected data Two fundamental approaches automated map compilation Vector: basic element from which all cartographic elements are formed is the X,Y coordinate pair. Raster: basic element from which all cartographic structures are formed is the picture element or pixel. Digitizer Vector Mode Approaches 7

3 Hardware for Vector Mode RulerRuler Semi-automatic digitizing tablet & tablet technology: Rail Rail and beam Tablet Tablet underlain with fine mesh of wires. SonicSonic Automatic line following 10 Modes of Digitizer Operation PointPoint Continuous interval StreamStream Switched Switched stream Continuous incremental StreamStream Switched Switched stream Vector Mode Capture Advantages Devices Devices inexpensive Need Need store only small part of image area High High resolution Disadvantage Not Not good for highly complex images-photos.

4 Raster Mode Hardware Raster Mode Capture ScannersScanners DrumDrum Flat Flat bed Flat-bed scanner 13 Raster Mode Capture Drum Scanner Advantages Highly Highly automated FastFast Disadvantages Costly Costly devices Large Large data storage requirements, but can convert to vector mode Next release of Arc Info will include Arc Scan at no extra cost.

5 Linear Photo Sensor Array Error Detection in Digitizing 18 Overview Review Review of typical error types. Error Error detection techniques. Common error types Error Error in line shape. Pseudo Pseudo polygons. Mislabeled polygons. Gaps Gaps and slivers.

6 Error in line shape Pseudo Polygons Correct Source Map Incorrect Digitized Map Correct Source Map Pseudo Polygon in Digitized Map Errors Error Label Errors Gaps and Slivers Correct Source Map Errors Label Errors Switched labels Correct Source Map Map with Gaps & Slivers Nonexistent Label Errors

7 Error Detection Techniques Error Detection Techniques Plot Plot map using fine line and compare to source. Display Display labels and plot to check for pseudo polygons. Display Display labels and plot to check for incorrect labels. In In short plot the map with a thin line weight and with labels displayed. Digitizing features: Button 1: capture points Simulation of process

8 Digitize first polygon: left button to capture; double click to end Attach map to digitizer Digitize second polygon: left button to capture; double click to end 31 Digitize third polygon: left to capture; double click to close32

9 Heads Up Digitizing Digitize fourth polygon: button 1 to capture; 2 to copy common; 4 to 33close 34 Overview Create Create new layers in Arc Catalog Run Run Arc Map and open the Editor Toolbar Load Load new layers Set Set Snapping Start Start editing DigitizeDigitize Correct Correct SaveSave Add Add attributes Setting snapping: environment & tolerances.

10 Digitize a Polygon Digitize a Common Border Polygon Polygon 1 Tool, Task, Target Avoiding Gaps and Slivers Avoided Gaps and Slivers Start here Polygon 2 Finish here Polygons with common border and no gaps or slivers

11 Delete a Vertex Polygon 1 is the existing feature. Polygon 2 is a new feature that shares a common border with polygon 1. To avoid gaps and slivers, select the autocomplete task and begin digitizing either within polygon 1 or at the location of a common vertex. Finish digitizing by double clicking within polygon 1. The program automatically stores the common verticies in polygon 2 so as to avoid gaps and slivers. Click Edit and then select Undo Add Vertex Modify a Feature Modify a Feature: Delete Tool, Task, Target Delete a Vertex

12 Modify a Feature: Insert Vertex Modify a Feature: Move Vertex Insert a Vertex Move a Vertex Modify a Feature: Finish Sketch Stop and Save To stop editing, click the Editor button to open the drop down menu and then click Stop Editing. To save edits, click the Editor button to open the drop down menu and then click Save Edits. Finish the Sketch

13 Overview of Rectification Map Rectification Add known & unknown layers Zoom to known Load georeferencing tool Fit unknown to display window Select control points [i.e., points in common] Check your work Rectify Add County [Known] Add Unknown & Set Display 2. Click Symbology Tab 3. Click Unique Values 1. Double click open Layer Properties Gloucester County New Jersey In NJ State Plane Coordinates 51 52

14 Erdas GIS Layer [Unknown] Zoom to Known Layer Zoom to Layer Zoomed to Known Layer Open Georeferencing Tools Open Georeferencing Toolbar 55 56

15 Fit to Display Two Layers Fit in Same Window Select Fit to Display Two Layers in same data view Tying Unknown to Known Points Select Control Points Links Dialog Magnifier click Window in Main Menu and select Magnifier Layers during Georeferencing 59 60

16 Tying Unknown to Known Points Unknown & Known Snapped Click here Second Click here first Tying Unknown to Known Points Unknown & Known Snapped Click here first Click here Second 63 64

17 Tying Unknown to Known Points Unknown & Known Snapped Click here first Click here Second Click here first Click here Second Check to See Fit Quality Keep Your Work Click here to make changes permanent 67 68

18 Specify Resampling Method & Save 69 70