LSGI3242 Digital Terrain Modelling and

Visualization Group Project

1. A brief description about the overall procedures in this project,

First, the mapping parameters are set, such as height and scale. After a

contour map is found, the process would move to tracing the contour lines and

inputting the contour values for making a digital terrain in a new project of

Genesis via Landscape Height field Editor, the interpolation of heights via trend

analysis which would interpolate the height of the terrain landscape with an

estimation of trend investigation, decide the area of flood with water. In this

project, a lake is created with this function.

To add the 3D features and other layers such as vegetation and urban layers

into the terrain, “Advanced” function would be used. Taking vegetation layer as

an example, using the Terrain Layers Editor, create the layer on the terrain model,

then create a vegetation layer by defining the size, type of vegetation and

color. Afterwards, using the Terrain Placement Editor provides the position for

the layer. Display the image and the viewing options are offered in Camera /

Target Editor.

08265400D Chan Ho Sing Ernest

08127165D Tai Pun Lung

2. Characteristics of chosen map:

The chosen contour map is composed of continuous

contour lines. It is easy for us to digitize the map. However,

there is a purple line in the middle of map and it is not a

contour. During the digitization, we need to avoid digitizing

it and it becomes a barrier of our project.

As we can see there is a Stream in the middle of map

surrounded with hills, the stream is not digitized as in the

terrrain model, it is rather difficult to trace one stream line

as river and display it. Therfore, a lake is created instead of a stream. A valley

is shown in the 1:2400 map, with the high density of the conotus, steep slope is

expected over the terrain at the bottom right corner. The height of slope is

descending from the skirts of the map to the middle.

The contours in this map is ideal for contour tracing as the contours are well

connected and are shown clearly. The clearness of the contours assists the

digistization not to confuse with one another during interpolation. Besides, the

number of contours is suitable for digitizing as the number of the contour line

differs from 0 to 850, in total, 17 contour line types. With the optimistic number

of contours, the digitization can be done effectively and avoid misleading contours

generated because of too many contours on the image, or else the terrain would

be too dense with contour information and later on the smoothing process can be

done in a clear manner.

A lake is produced at the

middle of the terrain

model

3. Description on interpolation method

The interpolation method is a grid based Bicubic spline interpolation method.

That is a smooth DTM surface over a patch consisting of four grid nodes is

constructed under a mathematical function (Li, Zhilin et al, 1960):

The interpolation used in this project is taking an approach of area based –

(patchwise) as the areal size definition. The best fitting approach of defining

the exactness of the size of the terrain area is also adopted with the Trend

analysis so that the deviation from the general trend in the area is taken into

account.

The Genesis software also provides the On-line quality control by conducting the

Trend Surface Analysis. As generally the terrain would have certain natural

trends of continuing spatial change behaviors. The trend analysis is done via

Least-square trend surface.

The Terrain model shown in

Genesis.

How about the nearest neighbour? Why didn’t you mention it?

4. Description on Camera, Target and View angle

The Camera, Target and the view angle of the

terrain model are set in the Camera and Target

Position Editor. Different placement of the above 4

mentioned items would lead to different views of the

terrain.

The Camera refers to the position of the viewer and

also from the height to observe the target.

The 2 images below show the difference of the placement of the camera and the

target without changing the height would lead to the difference of views of the

terrain model.

View 1 View 2

In this project, 2 approaches have been taken to view the terrain mainly beside

taking different angles, which are Fly-Through and Walk-Through (Li, Zhilin et al,

1960)

Fly-Through View Walk-Through View

Fly –Through provides a bird’s eye view continuously on viewing the terrain

landscape, in other words, viewing the model far above the surface.

Walk-Through refers to the human walking view, rather horizontal view.

5. Diagram(s),

The general image produced from the Genesis

The image indicates the function of the water

editor of the reflection in the water.

The image on the left presents the

function of the “atmosphere” by changing

the color of the atmospheric condition in

the image.

By changing the camera height and target

values, different images from different

angles and height can be obtained

The general image produced

with the vegetation cover added on to the

model.

Terrain model with Vegetation

cover and Urban feature added.

Terrain model with Urban layer

only

The image shown with the

vegetaion layer and the 3D

objects ( Wind Generators) on

the terrain

You gave a very detail description and explanation on each function in Genesis II.

6.Difficulties encountered in this project:

Searching a contour map form website is time consuming. It is because there

are lots of contour maps on internet and most of them are not suitable for this

project. Unclear contour or low contrast between contourlines and background

color can lead us hard to digitize. We spent a half and hour to find the map.

Since it is the first time for us to handle Genesis, we spent a lot of time on

digitizing. When there is a mistake on contour tracing, we have to do the whole

project once again or set the point to null one by one! It is frustrating during the

digitization.

Setting “Color Tolerance” and “Density” under Trance Parameters can help us

to digitize our map in different parts of the map. If the contour lines are to close to

each other, we need to turn our torlerance or it will choose a area of map to do the

digitization which is not correct. Then, mistakes again and digitized the map

again.

Furthermore, we spent a few days to edit the terrain and model. There were

lots of toothing problems when we got start. After opening a model and selecting

the plan of urban model, we placed the model on the 3D-map. There was nothing

changes after adding terrian and we had tried it a servel times. Finally, we found

that the size of model should be bigger! “20 meters” was too small for us to notice

that 3D model but we only saw the color of selected area was different form

others.

The continuity of the surface is poor, as the terrain model appears to be terrace,

though the area is preserved to be connected, but the landscape lacks the

continuity on the landform structure. Eventually, the trend analysis is done many

times to smoothen the terrain model.

7.Comments on the project:

It is a quite interesting project comparing with others assignments and sudjects.

Genesis provids us a platform to creat a 3D picture by editing atmosphere, clouds

or terrian.

Comparing 2D picture, 3D modle graph is more attractive to most of the

people during the persentaion of the terrain model. While contour map is mainly

for users with specified purposes such as getting the value of the height, a more

numerical information on the terrain area, the Genesis software aims at providing

a visualization process and an user experience related to the digitial terrain

modelling. The Genesis software allows the users make a tranformation from a

contour map to 3D graphics. The 3D images are easier for readers who do not

posses any map reading skills or techniques on understanding the chosen area

terrain and providing a more comprehensive idea to the users or stakeholders on

the landscape of the terrain model. In addition, the 3D graphics are better on

persenting the terrain model than the 2D contour map, as different views on the

terrain are offered.

The computers in the laboratory is not good enough to run Genesis. We have

to wait a long time(20 mins.) for the software to generate images. Furthermore,

saving or operation error always disturbed our progress. Luckly, department

provids Genesis II to us and it increase our working efficiency mostly.

8. Reference(s)

Li, Zhilin et al, 1960, Digital Terrain Modeling : principles and methodology

Bicubic Spline Interpolation P118-120

Fly Through and Walk Through for DTM Visualization P263- 266

Department of Surveying and Geo-Informatics

LSGI3242 Digital Terrain Modelling and Visualization

Group Project

Deliverables

Weight Weak (1-3) Average Good

A.

Organisation

and

presentation

1 The report is a copy

of the reference

materials. It is poorly

organised, contains

spelling and

grammatical errors,

has incorrect use of

technical

terminology, and

does not make

appropriate use of

citations and

references. The

appearance shows

lack of care and

attention to detail.

The report can be

understood but some

effort is required to

follow the structure. It

is obvious where

different group

members have

contributed to the

report. Some errors

in the use of

terminology,

grammar and

spelling. The

appearance could be

improved with a

small amount of

effort.

The report is coherent,

clear and concise, and

represents the work of the

group rather than a

collection of individuals.

The layout and order of

information is logical.

Correct use of grammar

and no spelling mistakes.

Correct use of references

and citations where

appropriate.

B. Brief

description

about the

overall

procedures.

Reason of

the chosen

map.

1 The overall

procedures are a

copy of the

instructions without

personal experience.

Only a brief

description is done

for the chosen map.

A personal

illustration of the

procedures through

the whole report is

given. The report

state the reason of

choosing the specific

map.

A tidy and clear description

of all the procedures

throughout the project. The

reason of choosing the

specific map is related to

the project and what you

learnt from the course.

C. A brief

description

and

explanation

about your

2 Unrelated details,

weak discussion,

poor or no analysis

or no reason.

Reasonably good

discussions, has

demonstrated the

logic flow and

relationship between

Has demonstrated deep

understanding of the topic

with sound discussions.

interpolation

method,

camera and

target

positions,

view angle,

etc.

the interpolation

methods

D.

Diagram(s)

2 Basic rendered

diagrams without

additional vegetation

cover and rendered

3D models.

Tried to play around

with different clouds,

sky and water to

render and generate

different pictures of

the terrain model.

A great effort is put to

render and generate the

terrain model with extra

vegetation cover and 3D

models.

E.

Comments

on the

project

2 It looks a description

of the procedures

instead of

commenting the

software and project.

It gives a fairly

comments on the

software and the

project. It shows the

technical problem

and how the group

solved the problem.

Critical comments are

given to improve the

software and the project.

Future recommendation is

made for future use.

Criteria Mark Weight Mark Comment

A. 7 1 7 Your report is well-organised and clear, but reference list is not correct. There is no introduction and conclusion in your project. Your report is within the page limited. You are the third group to use the same map.

B. 7 1 7 The procedures of your project are well-presented. You mentioned the characteristics of your map, but you didn’t show the reason of choosing it. You showed the origin picture of your map.

C. 10 2 20 You gave good descriptions and explanations on the factors for rendering the terrain surface.

D. 7 2 14 The rendered model looks fair, but you didn’t try to render different kind of surfaces with different kinds of 3D models. You can make use of the software to produce nicer and better terrain models.

E. 7 2 14 You mentioned about the limitations of Genesis II. You showed some difficulties about using the software, but you didn’t have any suggestions for future.

Total 8 62 Grade = (78%) B+ F < 40%, D >= 40%, D+ >+ 45%, C >= 50%, C+ >= 57%, B >= 64%, B+ >= 71%, A >= 80%, A+ >= 90%