Starting from Text Files. User Interface Graphic user interface –Mouse, buttons, windows, menus Commands-driven interface –Commands, parameters.

Starting from Text Files

User Interface

• Graphic user interface– Mouse, buttons, windows, menus

• Commands-driven interface– Commands, parameters

Integration

• Spatial data– Coverage– Shapefile– Import/Export– Text files

• Attribute data– INFO– DBF– Text files

Generate

GENERATE <cover>Arc: generate example2Generate: circlesTerminate input by entering ENDID,X,Y,Radius: 201, 3, 7, 2.0ID,X,Y,Radius: 202, 9, 4, 3.0ID,X,Y,Radius: endGenerate: quit

GENERATE: Examples

Here is a listing of a file named PT.FILE.1, 100, 1002, 99, 1123, 112, 1194, 121, 985, 107, 102ENDArc: generate ptcovGenerate: input pt.fileGenerate: pointsGenerating points...Generate: quitExternalling BND and TIC...

Arc: generate example7aGenerate: copytics example4Generate: 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

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: 803,10,10ID,X,Y: 804,10,0 ID,X,Y: end Generate: quit

GENERATE: More Examples

In this example, the code automatically generates the polygon label point and adds the closing vertex.Arc: generate example8bGenerate: 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}: 701X,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 example9Generate: 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

After GENERATE

• Use CLEAN and BUILD – Topology

• Precision– Whichever level in effect at the time

of using Generate

UNGENERATE

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

UNGENEATE: example

Arc: ungenerate point chcare chcare.ung

Import/Export

Arc: Export Cover Roads Roads(generates exported file roads.e00)

Arc: Import Cover Roads Roads1(generates coverage roads1)

Arc: Export Grid DEM DEMArc: Import Grid DEM DEM1

Exported coverage: a single file

• LAB• TOL• LOG• BND• PAT• TIC• …

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.

Spatial Data Creation and Spatial Data Conversion

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

Sources of data

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

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

Tablet digitizing

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

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

Coordinate space

Topology

• Independent of coordinate space• A result of actual relative locations

of real-world geographic features

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

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?

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

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.

Digitizing tolerances

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

Constructing topology

Record spatial relationshipsMinimize data redundancy

BUILD and CLEAN

• BUILD– Creates topology for points, arcs, polygons,

and annotation– Does not move/delete features– Fails when encounters intersections

BUILD <cover> {POLY|LINE|POINT|ANNOtation}

• CLEAN– Creates topology for arcs and polygons– Moves or deletes features– Alters coordinates of features

CLEAN <in_cov> {out_cov} {dangle_distance} {fuzzy_tolerance} {POLY|LINE}

Tolerances used with CLEAN

Converting Vector Data

Digital vector data

Evaluating digital data

Accessing digital data

Before obtaining digital data, be sure you know its format and that you have a device for reading it.

Georeferencing converted data

• CAD data – no georeferencing• GIS data

– Right map projection?– Correct topology?

• Transformation– Aligns tics to matching tics in a

georeferenced coverage

Transformation

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

• TRANSFORM

RMS error

Summary

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

Converting Vector Data

Digital vector data

Evaluating digital data

Accessing digital data

Before obtaining digital data, be sure you know its format and that you have a device for reading it.

Georeferencing converted data

• CAD data – no georeferencing• GIS data

– Right map projection?– Correct topology?

• Transformation– Aligns tics to matching tics in a

georeferenced coverage

Transformation

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

• TRANSFORM

RMS error

Summary

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