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LSGI4321

Geo-information For Urban

And Regional Studies

Individual Paper

By

Leung Cheuk Hin, 09241047D

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Situation

You are a GIT consultant. You are employed by the Development Bureau to prepare a

feasibility study for setting up a GIT portal for the new Tree Management Office for

monitoring urban tree. Discuss and suggest the system architecture, data standards

and other relevant issues in setting up this Portal.

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Part I. Feasibility Study

A. Existing situations

The awareness of the tree management has been significantly increased since the fatal

accidents caused by the falling of unhealthy trees in 2008 and 2010. There has been

much voice among the public for setting up an efficient procedure and standard to

manage trees properly so as to prevent any similar accidents happening again.

For this reason, the government officials have set up the Tree Management Office and

its website in 2010 to continuously monitor the trees’ conditions and allow public

participation in the process. Much information has been disclosed from its department

website (http://www.trees.gov.hk/tc/index.htm), including the management guidelines as

well as the assessment guidelines of the trees in the urban areas.

B. Constraints and solutions

The major hindrance of tree management is that there are too many trees even in urban

area. Apart from allocating enough manpower and resources for the inspection on site,

the processes of inspecting every tree on site and digitizing them on maps are very

time-consuming as well.

To solve this problem, one of the possible solutions is to classify the urban trees into

different categories with a consideration of the importance of the tree in the

environment.

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C. Details and the criteria of the tree classification

1. Potentially Dangerous Trees (PDTs)

Among different types of trees, those present danger to us should belong to the class of

Potentially Dangerous Trees (PDTs). Trees inside this class can be subdivided into

different groups with different urgency or importance.

Among different class of trees, higher class of importance may contain trees that pose

as an immediately danger to the neighborhood and should be handled as soon as

possible. While some other classes have less immediate threat to us, those trees

should still be managed from time to time to avoid any accidents. Trees might be

classified as the least importance if they are far from any urban facilities and unlikely to

give severe damage to the environment in case they fall off. In such cases the period

between on-site inspections may become longer so as to better allocate the manpower

resources and reserve them for the trees in the upper class.

2. Old and Valuable Trees (OVTs)

Apart from the conditions above, urban trees of special values and importance should

also be maintained as well. Thus there will be a group of Old and Valuable Trees

(OVTs) for classification. Trees belonging to this section may or may not have any

potential hazardous to the public but they should also be managed with care to better

conserve the environment.

According to the GovHK website by our government (2011), urban trees can be

classified old and valuable only by satisfying any of the following conditions:

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2.1 Trees of large size

A particularly large tree, either in the diameter and the circumference of the tree, its

height or the canopy spread, could be very important on the local habitat. The normal

average size of the tree's species may also be considered for reference. In government

the trees listed in this class must have its diameter more than or equal to 1m, canopy

spread more than 25m or must be at least 25m high.

2.2 Trees of precious or rare species

Rare items may indicate that the species might be difficult to survive in such a mild

climate in Hong Kong. Thus special care must be taken to prevent the extinction of the

species.

2.3 Trees of particularly old age (e.g. aged 100 or above)

Trees which are aged might have higher risk and pose as a more prominent threat to

the local environment so they must be especially cared. Since accurate age estimation

of the tree is almost impossible without cutting the tree, an alternative solution is to

compare the tree with those of other species to judge its age.

2.4 Trees of cultural, historical or memorable significance or of outstanding form

As these trees are related to citizens’ daily living, they should be monitored so as to

prevent controversial argument in case it falls off. Trees which are locally representative

or famous may also be another considering factor (e.g. the wishing tree in Lam Tsuen,

Tai Po).

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Part II. System architecture

A. Design

The core section of this tree management portal includes an internal web-based

database. It stores all the tree profiles which store all the information about the urban

trees. It also supports query searching such as SQL queries.

Another main component of this system is the portal interface for the external view. This

will be the place where the portal users perform tree management and analysis by

accessing, gathering or updating the tree information in the database.

Since the whole portal is web-based internet connection is a necessity to support the

system. Servers must be needed as a medium between the two components. Its role is

to monitor the usage and connection of the system. This will efficiently boost up the

system performance, especially when there are many concurrent users and they are

continuously updating the database.

For security issues and quality standards, the portal, database and the server have to

be maintained from time to time.

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B. Interface

(The above diagram is a template of GeoInfo Map, source: www.map.gov.hk)

As it is better to display the tree concerned in a digitized map in the Tree Management

Portal and to have a toolbar to perform various kinds of functions, it is quite similar to

the GeoInfo Map which helps to find different features’ locations. Thus we can base our

system on the Geo-Information Hub (GIH) provided by the Lands Department and we

can further develop it to enable search queries, GIS analysis and database operations

for tree management purposes.

Display of tree profiles will be on a tab on top of the map currently displayed. The profile

will show a profile picture, the basic and the location attributes to the local user while the

secondary class and the data modification button will only be available for Tree

Management Office or other related staff (See Part IV for data standards).

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C. Tree representation

Similar to many websites with map searches, this portal will also provide a background

interchange from 2D map, terrain map and to satellite images. However, digitization of

trees would be done by auto-tagging with coordinates on a geo-referenced map.

To create multiple views of the features, several layers will be used. They might include

different classes of trees to see their distribution and pattern, the distance the trees and

the living environment to see the how the trees affect their neighborhood. Creation of

different layers also makes analysis easier to handle.

D. Technologies involved

According to a similar system in Taiwan (Sun, 2009), the most important technologies

involved in this system architecture include RFID, GIS and GPS.

Among the listed technologies, RFID is used for tagging managed trees on-site, while

GIS is applied to enable spatial analysis and search queries from the portal user and

GPS is used for providing accurate coordinates of the managed trees.

Some other technologies might also be applied to maximum the usage of the system:

Laptops and smartphones with WIFI communication access can enable tree

management completion on-site, while query and analysis results can be transmitted to

other users by WIFI or Bluetooth communication. Last but not least, RSS may also be

applied onto the system so that subscribed users can learn about the newest update

almost immediately and continuously.

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E: Functions in the portal

First of all, a photo uploading function is essential for the profiles of the trees and for

easy reference. This function should limit the size of the uploaded photo such as 5MB at

most.

A data modification function for the officials will also be needed to maintain the urban

tree database. Officials can choose for a selective display of map information for tree

management analysis (e.g. positions, species or hazardous rating of the trees to be

presented). It is noted that the modification process will update the database first and

the name the official in charge for this update will be stored as a reference. Information

shown in the interface will then be corrected accordingly after the database update is

completed. To reduce the workload of the servers, the connection between the interface

and the database for update might vary, depending on the class of trees concerned.

Queries for the database can be provided for the users to search for particular

information while GIS analysis functions play an important role in this system as results.

Thus decisive results can be derived. For example a search for the distribution of the

banyan trees throughout the Kowloon Peninsula to see how banyan trees grow in Hong

Kong; a search for Melaleuca quinquenervia trees with a buffer distance 5m from the

edges of the road can be used to find out if there are any of these trees posing as a

threat to the road users; a search for old trees in urban recreational areas will give a list

of trees that if they fall off, the chance of getting injuries and facilities damage will

normally be higher. With the integration of these functions, tree management officials

can have a better judgment of what preventive measures will be taken and any bad

influences will then be minimized.

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Part III. Data standards

A. Basic attributes

Attributes in this part will give the most fundamental information about the tree.

For easy reference in the database system and for distinguishing the trees easily, each

tree recorded in the database will be assigned a tree identification number (Tree ID). An

ID mark should also be indicated on the tree for easy reference and inspection on site.

The dimensions of the tree will also be recorded, in terms of the Tree circumference, the

Tree diameter and the Tree Height. Area covered by the tree should also be recorded.

Apart from the dimensions, some other information that will be stored includes Tree

species, Tree age, Tree health conditions, Tree class and Facilities under the tree. For

more detailed studies, some other information such as Urban Cover and Soil Type

could also be stored.

For the risk management aspect, the risk degree will be stored according to the tree’s

basic condition, the environment. This data item should also be a means of

classification to separate trees which deserve more concern. Then two more data items

are needed to describe if the tree concerned has any Problems observed such as the

tree is harmed by the insects or decayed, and whether there are any Preventive

measures undertaken to protect us and the tree itself, such as stabilizing it with a rope.

After considering a similar case in Singapore (Shields, 2009), a data item for trimming

history of the tree is also included.

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B. Location attributes

Attributes in this part should provide geographical information of the tree, of which GIT

could be applied to digitize the tree onto the map.

In order to digitize the tree on the digital map, Coordinates of the tree must be provided

in HK1980 format and another item of the location in text format should also be required

as a reference.

Another item on this aspect is a Description of the neighborhood. To be concise, this

item may consist of a few short sentences, providing a means to easily relate the tree to

the surroundings. Moreover, for the convenience of the on-site identification some

dimension figures could be given, such as “13.08m apart from the nearest road” or “3m

from the nearest house corner of 66 Clear Water Bay Road”.

The last item which needed to be stored is the Existence and relative location of tree

groups. This reflects whether the tree is standing alone, being surrounded by other

trees or stands at the edge of a tree group, and is a key factor to check if such a relative

location has affected the growth of the tree.

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C. Secondary attributes

Data items in this part are not directly related to the tree but are also important for tree

management and analysis.

One of these items will be the Existence of constructions sites or slopes. This item is

needed to check whether the nearby environment causes some negative effects on the

tree. Slope registration ID might be provided if the tree concerned is located on a slope.

Some other data items in this category include any Authorization or permit required to

access the tree. The Date of the last update of the database and the Inspector

responsible for the last update are also recorded for administration purposes.

D. Visual factor – taking photos

Each tree stored in the system should be presented with at least one photo showing the

tree itself and the nearby environment. One tree may also have several photos.

Photos used in the tree profiles must be selected from the Tree Management Office and

must fulfill some requirements. For example, the size of the photos must be small so as

to reduce the demand on user’s computing software requirement.

Although it is very convenient to geo-tag the tree photos onto the digital map, that may

not be a good option. Geo-tagging allows capturing and uploading photos at the same

time so the photos have no time for suitability checking before publishing. The quality of

the photos is another arguable issue because the resolutions of the camera among the

smartphones are different, and they may not be as high as that of a digital camera.13

Part IV: Reference

Geoinfo Map (2009). GeoInfo Map | Map of Hong Kong provided by HKSARG.

Retrieved October 8, 2011 from Government of the Hong Kong Special Administrative

Region, Lands Deparrtment Web site: http://www.map.gov.hk

Govhk (2011). Register of Old & Valuable Trees. Retrieved October 21, 2011 from The

Government of the Hong Kong Special Administrative Region, Web site:

http://www.gov.hk/en/residents/environment/conservation/regoldvaluetree.htm

Shields, B. (2009). Singapore Uses GIS to Manage Large Urban Forest. In Forestry GIS

Journal. Retrieved October 4, 2011 from

http://www.esri.com/library/newsletters/forestry-gis-journal/forestrygj_summer_09/1.html

Sun, K. S. (2009). Development of Culture Assets Protection, Management, Display,

and Navigation System by Integrated by RFID, GPS、GIS, and Communication

Technology – Example by “Valuable Aged-Tree Management System.

Geographic Information System, 3 (4), 24-27.

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