Two Dimensional Arrays and Nested For Loops

APSC 177

Lab 5

1

Introduction

Digital Terrain Models (DTM), also called

Digital Elevation Models (DEM), are used in

many civil engineering applications.

DTMs are

created by measuring terrain elevation at

discrete points on a grid. One way to measure

elevation is with satellite radar.

Then

interpolation between grid points is

conducted to increase the resolution of the

model. A number of interpolation algorithms,

ranging from simple to very sophisticated,

have been developed.

In this lab, you will write a C++ program,

making use of for

loops, to interpolate a

matrix (grid) of numbers that represent

elevations.

Pre

-

lab

Pseudocode

Before

you

r

lab class,

write pseudocode

for your proposed program

(see program

specification below)

.

Only write pseudocode for

the code that you write. Do NOT write

pseudocode for the starter code that you are given. Remember that pseudocode is

similar to code but is written in English and is programming language independent.

There are many ways/styles that pseudocode may be writ

ten. The most important

factor that determines whether your pseudocode is good or not is how clearly it

describes what needs to be coded. If your lab marker can easily understand your

pseudocode suc

h that he/she could implement it in

code, then your pseudocode is

good.

You may produce your

pseudocode

on a computer and print it, or, you may

NEATLY your

write your pseudocode

by hand on a piece of paper. Your

pseudocode

is

due at the START

of your lab class and is worth 2

0% of this labs

grade (see the APSC 177

Lab Guide).

Program Specification

We will implement a very simple interpolation algorithm in this lab.

Each interpolated

value

will simply be the arithmetic mean of the closest values around it. Consider a

4

by

4

square

matrix of

numbers as represented by the diagram below.

APSC 177

Lab 5

2

We wish to interpolate between each pair of numbers (both horizontally and vertically)

such that the result is the 7 by 7 matrix below.

We will do the interpolation in steps.

1.

Calculate each interpolated

value represented by a

by calculating the

average of the 4 numbers around it represented by

.

APSC 177

Lab 5

3

2.

Calculate each interpolated value represented by

a

by calculating the

average of the four numbers around it as follows

3.

Calculate each interpolated value represented by a

by calculating the

average of the three numbers around it as follows

Note that the above interpolation algorithm assumes a

starting data

matrix with

minimum

dimensions of

3

by

3

.

In

the Vocareum Lab 5

assignment

you will find starter code that does everything

required EXCEPT calculate the interpolate

d values.

DO NOT change or delete any of the

starter code.

Study the starter code so that you understand it.

Your task is to add code (where indicated by the comments in the starter code) to

calculate the interpolated values.

Your code must be able to ha

ndle a starting square

matrix of

any

size larger than 2 by 2.

Remember to add comments to your code.

Use

one set of

nested

for

loops to calculate

the interpolated values in step

1

. Use two

sets of nested

for

loops to calculate

the interpolated values in step 2 (note the two

two scenarios in step 2).

Use individual

for

loop

s

to calculate the interpolated values

in

each of the

top row

, most lefthand column, most righthand column, and bottom row

(four scenarios in step 3

)

.