1. UNIVERSITY OF GHANA
DEPARTMENT OF GEOGRAPHY & RESOURCE
DEVELOPMENT
NAME : SELASE KWAMI
I.D.NUMBER : 10452218
COURSE : GEOG 344 GEOGRAPHIC INFORMATIONS SYSTEMS
LECTURERS : DR GERALD YIRAN AND BARIMA OWUSU
PHONE NUMBER : 0264562312
2. LAB REPORT IV
Questions?
1. Choose one school or any of the data you are using ‘Extract part’ of your work and save it as a
different shape file. Explain in your own words the meaning and functions of your choice?
2. Choose one ‘Overlay’itemandperformusingyour data. Explaininyour own words,the meaning
and functions of your choice.
3. Bufferaroundapoint,aline orapolygonat adistance of 1000m anddisplayyourresults.Compare
this buffer and the buffer distance chosen in activity 2 i.e. ‘Selection by Location’. What is the
difference ?
4. Choose one ‘Statistics’ item and perform with your data. Explain your results.
3. Answers
1. Stepson how to performclip
Open ArcMap
Connect to folder and load your files
Open Arc tool box and expand Analysis tools.
Expand the extract option and click on Clip
NB : Before selecting your input feature,you may need to do a projection if the original
projection of your point or line feature does not match that of your polygon.
Choose input feature of your choice. For example AMA roads project.
Choose output feature of your choice For example Accra metro.
Click OK and wait for Clip to take place.
Essence of the Clip function : This function clips a raster using a rectangular shape according to the
extents defined or will clip a raster to the shape of an input polygon feature class. The shape defining the
clip can clip the extent of the raster or clip out an area within the raster.
The inputs for this function are the following:
Input Raster
Type—either Outside or Inside
Clip Extents
The Clip Extents can be defined by a dataset. By default, it uses the envelope of the dataset; however, if
there is a polygon feature within the dataset it will clip to the shape of the polygon. Alternatively, you can
specify the x and y minimum and maximum coordinates. If you choose the Outside clip type, then the
imagery outside the extents will be removed. If you choose the Inside clip type, then the imagery within
the extents will be removed.
4. Image of clip function
2. Steps on how to perform spatial join
Open ArcMap
Connect to folder and load your files
Open Arc tool box and expand Analysis tools.
Expand the Overlay option and click on Spatial Join.
Select target features, join features and join operation.
Click ok and wait for spatial join to take place.
Essence of Spatial join : This function joins attributes from one feature to another are
based on the spatial relationship between target and join features. The target features and
the joined attributes from the join features are written to the output feature class. A spatial
join involves matching rows from the Join Features to the Target Features based on their
relative spatial locations.
5. Image of Spatial Join function
3. Steps on how to perform Buffer/proximity analysis
Open ArcMap
Connect to folder and load your files.
Open Arc tool box and expand Analysis tools.
Perform a clip.
Expand Proximity Options
Click Buffer
Input feature must be the same input feature you used in performing your
clip.
Enter linear unit (change to metres) and select distance of your choice.
Select the (ALL) option as your dissolve type.
7. 4. Summary Statistics
Open ArcMap
Connect to folder and load your files
Open Arc tool box and expand Analysis tools.
Expand Statistics option
Click Summary Statistics
Select input table i.e. Ghana_Districts
NB: Input table must have an attribute with integer value fields.
Select statistics field and statistic type and click OK.
Summary Statistics image
Afterperformingsummarystatistics,atable containingfieldnamesObject_ID,Frequencyand
SUM_Shape_Lengthwascreated.I obtainedmyresultsbyselectingShape_length asmyStatisticsfield
and Mean as my Statistics type. Iobtainedasingle value because meanisthe average of the shape
lengthortotal sumof lengthsdividedbythe numberof individual lengths.
