# Introduction to Geographical Information Systems

Pages: 27 (4188 words) Published: February 7, 2015
GGH 3703
INTRODUCTION TO GEOGRAPHICAL INFORMATION
SYSTEMS
ASSIGNMENT 6
LETTY POSH MABUNDZA
44006144

1

Assignment cover

page 1

Question 1

page 3-4

Question 2

page 4-6

Question 3

page 6-9

Question 4

page 10-14

Question 5

page 14-15

Question 6

page 15-16

Sources consulted

page 17-18

2

QUESTION 1:
Given data:
 Mean annual temperature
 Average annual air pressure
 Boundaries of provinces
 Climate data
 Location of meteorogical stations
Spatial data:
 Boundaries of provinces
 Location of meteorogical stations
Attribute data:
 Mean annual temperature
 Average annual air pressure
 Climate data
 The raster data model uses a grid to cover the space and the value of each cell (pixel) in the grid to correspond to the characteristic of the geographic feature at the cell location. The cell is the smallest unit in the grid. A grid is a matrix of cells. Raster data is best used when your primary concern is with the locational relationships of the phenomena represented by geographic features and not the features themselves. A vector data model is a representation of the world using points, lines, and polygons. Vector models are useful for storing data that has discrete boundaries, such as country borders, land parcels, and streets  For mean annual temperature I will use a raster data module because the temperature of places have different values it is a continuous data because values can change at any time.

 For average annual air pressure I will use a raster data module because it is also a continuous data and the air pressure can change over a period of time and I will use lines to represent air pressure.

 For the boundaries of the provinces I will use a vector data model, as it is a discrete boundary and I will use points to classify the layers.
 For climate data I will use a raster data model, as values change from time to time, and values can be calculated.
 For the location of meteorogical stations I will use a vector data model, and I will points to classify the layers.
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 Types of scales:
 Mean annual temperature is an interval scale because from the map we will be able to tell the exact value between the places in South Africa. The data is continuous.
 Average annual air pressure is an interval scale because we will be able to see the exact value between values in different places and it is consistent and we can measure it. The data here is continuous  Boundaries of provinces are a nominal scale, because we will be given the name of the province and the name will not change. The data here is discrete.

 Climate data is an interval scale because here we will get values over long periods and be able to see the difference of previous results of the different places. The data here is continuous.  Location of meteorogical stations is a nominal scale since we will have the name of the place where the stations are located. The data here is discrete.

 Attribute data is information appended in tabular format to spatial features, here the locations of meteorogical stations will be the spatial data that the attribute data will be linked to, for example, the mean annual temperature, the climate data, and the annual air pressure data. QUESTION 2:

1. If we say a map has a scale of 1 to100 000 (expressed as 1:100 000), we mean that a distance of 1 inch on the map represents 100 000 inches in the real world. With digital maps, the concept of scale in terms of distance does not apply because digital maps do not remain fixed in size. They can be displayed or plotted at any possible magnification. In digital mapping, the term scale is used to indicate the scale of the materials from which the map was made. For eg. If a digital map is said to have a scale of 1:100 000, it was made from a 1:100 000 scale paper map. Even if there is no scale in a digital world, we use scale as a concept to generalize graphical and model...