GEOG 05344

Geog 05344

Introduction to Geographic Information Systems

Instructor: Dr. P.C. Lai

Email: pclai@hkucc.hku.hk

1. Objective

2. Tentative Outlines of Practical Sessions

3. Course Project

4. Reference

5. Lecture Notes

6. Case Study

Objective

In this course, students would go through a problem-based project in phases to learn about techniques and procedures required to establish a functional GIS. The project comprises 5 consecutive phases. Phases 1 to 3 will require students to collect and input geospatial data for their case studies. Students need also to apply spatial query and analytical techniques in Phase 4 to attain specified goals of the project. Presentation of findings in the form of thematic maps, charts, and others conclude the project in Phase 5.

A Tentative Outline of Practical Sessions

Phase	Weeks	Content	Description
1	1-2	Data Automation - Part 1: Digitisation	preprocessing: geographic data encoding spatial data capture with the ADS semi-automatic digitisation function in PC ARC/INFO
2	3-4	Data Automation - Part 2: Editing Data Error	fixing geometrical and topological errors of spatial objects in PC ARCEDIT
3	5-6	Attribute Data Input	attaching meanings to spatial objects
4	7-9	Cartographic Modelling	conducting simple queries on spatial objects performing spatial analytical functions to seek relationships
5	10-12	Presentation of Findings	data presentation: compose thematic map

Course Project

Each student will attempt a case study as the course project. The course project involves the Problem-Based Learning approach (http://edweb.sdsu.edu/clrit/learningtree/PBL/WhatisPBL.html) whereby a student will design and undertake a path of learning based on individual initiatives and choices. Throughout the course, students would acquiant themselves with fundamental concepts and techniques essential to establishing a workable GIS.

The course project has five identifiable phases outlined earlier:

Phase 1	Data Automation - Part 1: Digitisation
Phase 2	Data Automation - Part 2: Editing Data Error
Phase 3	Attribute Data Input
Phase 4	Cartographic Modelling
Phase 5	Presentation of Findings

Phase 1 Data Automation - Part 1: Digitisation

Task:

To prepare a digital map file on the 1996 TPU boundary for Shatin (see Map 1). The digital map file must contain the necessary attribute tables.

Objective:

To acquiant students with the procedure and technique of digitisation, in particular, the ADS program of pcARC/INFO.

Source:

The 1996 Hong Kong Population By-Census - TPU boundary of the New Territories

It is required that you read this note and all reference materials before attending the practical sessions. You would be assigned a case study in the first practical session.

I. Digitisation

1. Study the pcARC/INFO ADS program and familiarise yourself with the digitising procedure prior to the practical session (Reference 1 is available from the GIS Lab).

2. Preprocessing: geographic data encoding

a. Examine the map manuscript and decide if encoding is necessary.

[Hint: Encoding is essential to facilitate attribute data input and ensure data integrity]

2. Digitisation

a.Mount the map manuscript on the digitising tablet

[Note: make sure that Shatin is within the active area of the digitising tablet]

b.Invoke pcARC/INFO by typing ARC and begin digitising the TPU boundary with ADS.

i/ Initiate ADS by typing ads and name the digital map or coverage TPUST.

[Hint: You can view the arguements of each command by typing usage {command} and obtain a more detailed usage of a command by typing help {command}]

ii/ Establish at least four tic points, as marked on the map manuscript.

iii/ Trace the boundaries of TPU 7.5.3 to TPU 7.5.9 using the Arc-Node digitising method.

[Hint: Use 2 to indicate terminal or end points and 1 for intermediate points along a line]

iv/ Affix a label point to every TPU region.

[Hint: Each label point should be a unique identifier, i.e. a numeric user-id should not be repeated. Uniqueness is necessary to ensure an exact identification at a later stage.]

v/ Quit ADS upon completion of the digitisation process.

3. Use the CLEAN command to construct polygon topology and name the 'cleaned' file or coverage TPUSTC.

4. Use the DESCRIBE command to list the summary statistics of the content of your coverage.

5. Type list tpustc.pat to display the data content of the cleaned TPU coverage named TPUSTC.

II. Assignment

A. Answer the following questions:

1. What is a tic and what is its function?

2. Contrast between the Arc-Node and the Spaghetti digitising methods.

3. What is the significance of label points in a (a) polygon and (b) point coverage?

4. What is topology?

5. Is there another command other than the CLEAN command to construct topology?

B. Submit a copy of the data contents of TPUSTC.PAT and account for the content of TPUSTC. [Hint: press the print screen key once while listing the contents of the polygon attribute table.]

Phase 2 Data Automation - Part 2: Edit data error

Task:

To rectify geometrical errors in the digital map file of 1996 TPU boundary for Shatin.

Objective:

To make TPUSTC usable and ensure data integrity.

Read this note and Reference 2 before attending the practical sessions.

I. Error Edit

1. Identify geometrical errors in TPISTC (see Appendix I). Generate a plot of the tics, lines and errors of TPUSTC using the EDITPLOT command.

2. Type draw tpustc.plt to view the plot created using EDITPLOT.

[Hint: help editplot shows the usage of the command]

3. Having identified all the node and label errors, invoke ARCEDIT to edit the errors interactively.

4. Initiate ARCEDIT by typing arcedit.

a. Set the edit environment

i/ display 4 (set the display to screen)

ii/ mapex TPUSTC (set TPUSTC to fit on screen)

iii/ edit TPUSTC (read TPUSTC)

iv/ editfeature {line / node / label} (specify the type of feature to edit)

v/ Save as TPUSTE when done with editing.

[Note: use a new file name wherever possible to retain the original file]

5. Reconstruct the topology of the edited map to verify that all errors were edited.

[Hint: you may reconstruct the coverage topology using either the CLEAN or BUILD command.]

6. Examine if node and label errors were corrected.

a. nodeerrors tpuste (list nodes with geometrical errors)

b. labelerrors tpuste (list polygons with no label or more than one labels)

c. Return to Step 1 if errors remain.

[Note: Repeat all steps as many times as necessary until the edited file contains no error. Remember to specify appropriate file names]

II. Assignment

Answer the following questions:

1. Give an account of the geometrical errors identified in TPUSTC? What are the possible causes for these errors?

2. Why is it necessary to reconstruct the topology of TPUSTE?

3. Which command did you use to reconstruct topology in Step 3? Explain you choice.

4. We may specify fuzzy and dangle tolerance in CLEAN. Explain their usage.

5. ARC/INFO has built some automatic routines e.g. CLEAN to correct geometrical errors inside a coverage, then why is it necessary to edit the errors interactively.

Phase 3 Attribute Data Input and Look-up Table

Task:

To add attributes (i.e. assign meanings) to the digital map file of 1996 TPU boundary for Shatin.

Objective:

To acquaint students with data manipulation in the TABLES environment (a Relational Data Base Management System) of ARC/INFO.

Read this note and Reference 3 before attending the practical sessions.

I. Adding bi-census data to TPUSTE

1. Add population data to TPUSTE to facilitate data analysis. The procedure requires you to input the data by keyboard entry.

a. Initiate TABLES by typing tables at the ARC prompt.

i/ sel tpuste.pat (specify the attribute table to edit)

b. Examine the contents of TPUSTE.PAT:

i/ items (list the fields or column labels of TPUSTE.PAT)

ii/ list (list the records or row values of TPUSTE.PAT)

c. Adding new attributes, step 1.

i/ additem (create a new field or column for storing records)

[add an integer field or item named POP with an item width of 8 spaces]

d. Adding new attributes, step 2.

i/ update (add records or rows to the new field)

[Refer to Tables 3.1 for population data by TPUs]

e. Add employment data to TPUSTE. The employment data by TPUs are stored in an INFO file named CENSUS.DAT under the directory F:\DATA\05344.

f. Quit TABLES and return to the ARC environment. Copy the INFO file into your own directory.

copyinfo f:\data\05344\census.dat census.dat

g. Add employment data to TPUSTE using the field named EMPLOY.

h. Repeat steps 1a - 1d above to create a new field or column for storing records.

[Hint: Refer to the item named EMPLOY in CENSUS.DAT for the item definition]

i. Add records or rows to the new field by relating items between two attribute tables.

i/ join census.dat (relate INFO files using a common item)

ii/ list

iii/ calculate employ = $employ (copy employment data into TPUSTE)

iv/ cancel file relate by typing join off and list to ensure the data have been copied.

II. Usage of a Look-up Table

1. You may classify the TPUs of Shatin according to their population level with the use of a look-up table. (Read Reference 3 for other uses of a look-up table)

a. Get into TABLES to create a look-up table for TPUSTE

i/ define tpuste.lut

b.add two items to the look-up table

POP (width 8, type i for integer)

SYMBOL (width 2, type i)

c. add records to POP and SYMBOL (refer to Table 3.2) using the add command.

d. Quit TABLES.

2. Use the look-up table in mapping.

a. arcplot (initiate the ARCPLOT map display environment)

b. mapex tpuste (fit TPUSTE to screen)

c. polygonshades tpuste pop tpuste.lut (shade TPUs according to values in the look-up table)

III. Transformation

1. Transform the digital map from digitizing unit to real world reference unit, in the case of Hong Kong, 80 Grid.

a. Create an empty file containing only tics

i/ create TPUT TPUSTE

b. Update the x,y coordinates of tics points in TABLES

c. Transform the coverage using the TRANSFORM command. (type usage transform to view the usage of the command)

III. Assignment

Answer the following questions:

1. Differentiate between the ARC, ARCEDIT and TABLES environment.

2. What is an INFO file? What is a PAT?

3. Describe the usage of JOIN. What is the join item used to relate TPUSTE.PAT and CENSUS.DAT?

4. Discuss the usage of a look-up table. Explain the purpose of the items in TPUSTE.LUT.

Phase 4 Cartographic Modelling

Task:

To render procedures for cartographic modelling that produces maps as outputs.

Objective:

To examine the spatial analytical capabilities of ARC/INFO.

Read this note and reference 4 before attending the practical sessions.

Remember to copy the datasets specified in your task sheet into your own directory.

I. Visual examination of the datasets

1. Type arcplot at the ARC prompt to invoke ARCPLOT.

2. Set the graphics device to display on screen. Specify TPUSTE for viewing.

[Hint: Review II.3. of Phase 3]

3. Draw spatial features of TPUSTE using different symbols.

a. arcs tpuste (draw line features)

b. polygonshades tpuste tpuste# (shade polygons accoding to values of TPUSTE#)

c. polygontext tpuste tpuste-id (label polygons with TPUSTE-ID)

[Repeat steps 2 and 3 to view spatial features of other datasets. Appendix 2 contains additional commands for drawing spatial features.]

II. Data manipulation

1. Compute population density

a. Initiate TABLES and sel tpuste.pat to edit.

b. Add a new item named DENSITY (a Numeric item with a width of 4 and 2 decimal places, allowing 9999.99 as the largest value) to TPUSTE.PAT to store population density data.

c. Compute population density by dividing population numbers (POP) with AREAs of the corresponding TPU polygons.

calc density = pop / area

d. Divide the TPUs into two classes according to their density levels and map them.

[Hint: Reviewe II of Phase 3 for instructions]

III. Cartographic Modelling - Buffer and Spatial Overlay

1. Buffer

a. Explore the usage of the BUFFER command.

i/ buffer test lbuf # # 200 line round full (Create 200 metre buffer zones with round corners for line features in TEST and store the buffers in a new file named LBUF)

ii/ buffer test ptbuf # # 300 point flat (Create 300 metre buffer zones with ?? for point features in TEST and store the buffers in a new file named PTBUF)

iii/ buffer testpoly pybuf # # 50 poly round right (Create 50 metre buffer zones on the right side of the polygon outlines in TESTPOLY and store the buffers in a new file named PYBUF)

[Note: Use the arcs command in ARCPLOT to view or draw the various buffers.]

b. Customise the BUFFER command to address the conditions specified in your case study.

2. Spatial Overlay

a.Three commands are available in ARC/INFO for spatial overlay: IDENTITY, INTERSECT, and UNION.

i/ identity lbuf cov idcov (Overlay LBUF with COV to create IDCOV)

ii/ intersect lbuf cov incov (Overlay LBUF with COV to create INCOV)

iii/ union lbuf cov uncov (Overlay LBUF with COV to create UNCOV)

[Note: Use the arcs command in ARCPLOT to examine the effects of the above commands.]

b. Choose the spatial overlay commands appropriate for your case study.

IV. Assignment

Answer the following questions:

1. Provide a brief description of the principal functions of the ARCPLOT module.

2. Suggest two possible conditions that require the BUFFER command.

3. Compare and contrast the three spatial overlay techniques in III.2.a above.

4. With reference to III.2.a.i above, what would happen if the order of LBUF and COV was swapped.

5. Explain your choices in III.1.b and III.2.b above.

Phase 5 Data Display and Presentation

Task:

To prepare relevant maps as supplement to the Project Report.

Objective:

To acquaint students with interactive map making procedures.

Read this note, Reference 5 and attend the scheduled demonstration before starting the practical.

I. Map Composition

1. Prepare draft manuscripts for your required maps.

2. Set up the ARCPLOT environment for map composition.

a. pagesize 8 11 (set the output size to portrait A4)

b. maplimit page (fit drawings to page)

c. map {composition_name} (Specify a directory name to store your map composition; Supply a new name for each map.)

d. Draw map features using ARCPLOT commands.

[Note: The specification of a {composition_name} in I.2.c. above enables features drawn in ARCPLOT to be stored as graphic elements in the specified directory. These graphic elements can be re-sequenced, scaled, or moved.]

3. Add a map legend.

a. Prepare a key file for the legend (sample below: An example of a keyfile for Population Distribution).

4. Insert the legend in your map:

a. keyposition * (pinpoint the position for the upper left corner of your legend)

b. keybox .15 .1 (set the dimensions of the boxes for shading symbols to be 0.15" in width and 0.1" in height)

c. textsize .1 (set the size of the text character to be 0.1" in height)

d. keyshade {keyfile} (draw the legend with shading symbols and descriptions specified in the keyfile created in I.4.a above)

5. Include a map title:

a. move * (pinpoint the position for the lower left corner of the text string)

b. textsize .2 (use a larger text size of 0.2" to write the map title)

c. text 'text_string' (quote the text_string within the apostrophes)

5. Improve your map by including relevant descriptors:

[Note: Appendix 2 has additional commands for drawing lines, arrows, boxes, North indicator and commands for selecting colours and symbol patterns.