Starting from Text Files

1
Starting from Text Files
2
User Interface

• Graphic user interface
• Mouse, buttons, windows, menus
• Commands-driven interface
• Commands, parameters

3
Integration

• Spatial data
• Coverage
• Shapefile
• Import/Export
• Text files
• Attribute data
• INFO
• DBF
• Text files

4
Generate

• GENERATE ltcovergt

Arc generate example2 Generate
circles Terminate input by entering
END ID,X,Y,Radius 201, 3, 7, 2.0 ID,X,Y,Radius
202, 9, 4, 3.0 ID,X,Y,Radius end Generate quit
5
GENERATE Examples
Here is a listing of a file named PT.FILE. 1,
100, 100 2, 99, 112 3, 112, 119 4, 121, 98 5,
107, 102 END Arc generate ptcov Generate input
pt.file Generate points Generating
points... Generate quit Externalling BND and
TIC...
Arc generate example10 Generate tics Enter
Tics. Terminate input by entering END at ID,X,Y
prompt. ID,X,Y 801,0,0 ID,X,Y 802,0,10
ID,X,Y 803,10,10 ID,X,Y 804,10,0 ID,X,Y end
Generate quit
Arc generate example7a Generate copytics
example4 Generate points Enter points.
Terminate input by entering END at ID,X,Y
prompt. ID,X,Y,Angle,Scale 601,3,7
ID,X,Y,Angle,Scale 602,9,7
ID,X,Y,Angle,Scale 603,5,4
ID,X,Y,Angle,Scale end Generate quit
6
GENERATE More Examples
In this example, the code automatically generates
the polygon label point and adds the closing
vertex. Arc generate example8b Generate polys
Enter polygons. Terminate polygon by entering
END at X,Y prompt. Terminate input by entering
END at ID,X,Y prompt. ID,AUTO X,Y 701 X,Y
3,9 X,Y 4,5 X,Y 8,4 X,Y 9,7 X,Y 6,9 X,Y
end (Label for ID 701 placed at
6.242,6.809) ID,AUTO X,Y end Generate quit
Arc generate example9 Generate polygons Enter
polygons. Terminate polygon by entering END at
X,Y prompt. Terminate input by entering END at
ID,X,Y prompt. ID,AUTO X,Y 701,auto X,Y
3,9 4,5 8,4 9,7 6,9 3,9 X,Y end
(Label for ID 701 placed at 6.242,6.809) ID,X,Y
end Generate quit
7
After GENERATE

• Use CLEAN and BUILD
• Topology
• Precision
• Whichever level in effect at the time of using
  Generate

8
UNGENERATE
9
GENERATE In actual use

• Two parts
• Text file (coordinates)
• DBF file (attributes)
• Use Generate with Text file to create a cover
• Use DBASEINFO to convert DBF to INFO table
• Use JOINITEM to join two parts together

10
UNGENEATE example

• Arc ungenerate point chcare chcare.ung

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Import/Export
Arc Export Cover Roads Roads (generates exported
file roads.e00) Arc Import Cover Roads
Roads1 (generates coverage roads1) Arc Export
Grid DEM DEM Arc Import Grid DEM DEM1
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Exported coverage a single file

• LAB
• TOL
• LOG
• BND
• PAT
• TIC

13
Assignment

• From ArcDoc, answer
• How to generate a coverage with annotation in
  it?
• How to generate curves?
• How to generate a fishnet?
• Using the steps demonstrated in class and data
  files downloaded, create coverages for welfare,
  company, bus, and road
• Using ArcGIS, create a map that shows all
  coverages.
• Export the map into a graphic file and then email
  to me as the submission.

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Spatial Data Creation and Spatial Data Conversion
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Spatial data considerations

• Converting an existing digital dataset into GIS
  database
• Creating from ground zero
• Georeferencing a paper map
• Tracing geographic features
• Adding attributes
• Building topology
• Validating data
• Creating metadata

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Sources of data
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Capturing data

• From hardcopy spatial data
• Scanning
• Taking a digital picture of the map
• Digitizing
• Tracing the map with a tracing device
• Heads-up digitizing
• Combination of scanning and digitizing

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Scanning

• Creates a raster image of a hard-copy map
• The raster image can be vectorized
• ArcScan, ARC GRID
• Units inches, centimeters, pixels
• Requires georeference

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Tablet digitizing

• Produces a vector coverage
• Unit digitizer unit (e.g., inches)
• Requires georeference
• Can use ADS, ArcEdit
• Can be rasterized ARC GRID

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Heads-up digitizing

• Combines scanning and manual digitizing
• Maps are first scanned, georeferenced, and then
  displayed on screen for tracing features
• Pros
• Fast,
• allowing error-correction,
• Cons
• Possible errors

21
Coordinate space
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Topology

• Independent of coordinate space
• A result of actual relative locations of
  real-world geographic features

23
Data automation

• Accuracy of spatial data and attributes affect
  the accuracy of analysis results
• Data automation process is critical in
  implementing any GIS
• No data,
• No analysis of data,
• No results

24
Automation considerations

• Which method of data capture will be used?
• How will data be referenced to the real world?
• Will BUILD or CLEAN be used to construct topology?

25
Georeferencing with a master coverage

• Master coverage
• A georeferenced coverage
• Used to georeference all other spatial data in
  database
• Coordinates in the master coverage are normally
  in real-world coordinates already
• Created by
• Type up/import coordinates into a dbase file
• Use CREATE to initiate an empty coverage
• Use TABLES/ADD to add coordinates

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Master coverage

• You can use ArcInfo to copy the tics from the
  master coverage before digitizing, or
• You can use the master tics to move coverage
  features to a different coordinate space after
  digitizing.

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Digitizing tolerances

• To reduce errors
• Weed tolerance
• Arc snap
• Node snap
• Arc intersect

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Constructing topology
Record spatial relationships Minimize data
redundancy
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BUILD and CLEAN

• BUILD
• Creates topology for points, arcs, polygons, and
  annotation
• Does not move/delete features
• Fails when encounters intersections
• BUILD ltcovergt POLYLINEPOINTANNOtation
• CLEAN
• Creates topology for arcs and polygons
• Moves or deletes features
• Alters coordinates of features
• CLEAN ltin_covgt out_cov dangle_distance
  fuzzy_tolerance POLYLINE

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Tolerances used with CLEAN
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Converting Vector Data
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Digital vector data
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Evaluating digital data
34
Accessing digital data
Before obtaining digital data, be sure you know
its format and that you have a device for reading
it.
35
Georeferencing converted data

• CAD data no georeferencing
• GIS data
• Right map projection?
• Correct topology?
• Transformation
• Aligns tics to matching tics in a georeferenced
  coverage

36
Transformation

• Converts coverage coordinates from one coordinate
  system to another through
• Translation (shift)
• Rotation
• Scaling
• TRANSFORM

37
RMS error
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Summary

• Sources of data
• Tools for data conversion
• Data automation
• BUILD and CLEAN
• Georeferencing spatial data
• TRANSFORM

39
Converting Vector Data
40
Digital vector data
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Evaluating digital data
42
Accessing digital data
Before obtaining digital data, be sure you know
its format and that you have a device for reading
it.
43
Georeferencing converted data

• CAD data no georeferencing
• GIS data
• Right map projection?
• Correct topology?
• Transformation
• Aligns tics to matching tics in a georeferenced
  coverage

44
Transformation

• Converts coverage coordinates from one coordinate
  system to another through
• Translation (shift)
• Rotation
• Scaling
• TRANSFORM

45
RMS error
46
Summary

• Sources of data
• Tools for data conversion
• Data automation
• BUILD and CLEAN
• Georeferencing spatial data
• TRANSFORM