LESSON NOTE ON THEODOLITE Part A

USE of THEODOLITE

Introduction

The theodolite is a versatile instrument and is commonly used for the following tasks.

a)      Measurement of horizontal angles

b)      Measurement of vertical angles

c)      Setting out horizontal angles

d)      Ranging

e)      Levelling

f)        Optical distance measurement

g)      Controlling verticality

 Measurement of horizontal angles

The reiteration method is a common method of observing horizontal angles.  The procedure is as follows:

a) Accurately center and level the theodolite over a ground mark

b)      Sight the left hand target (face left) with a small reading on the plate using the lower plate clamp and slow motion screw.  Do not touch the lower plate again
during this round of angles.  If several rounds of angles are to be observed, the initial plate setting is changed by about 90 each time.

c)      Sight on to the right hand target(s) using the upper plate clamp and slow motion screw, noting the reading each time.

d)      When the last target has been sighted, change face,  This is done by rotating the telescope vertically through 180 and the upper plate horizontally though

180 to sight back onto the last target.

e)      If face right re-observe all the targets.

f)      It is essential that the plate readings are checked for accuracy on completion of each round of angles.  Check that there is 180 difference between the
readings.  Any variation from the 180 difference is an indication of instrumental error and should be reasonably constant.  This will discover gross errors due to
misreading scales, using wrong slow motion screws, sighting wrong targets, etc. The targets can be re-sighted and the readings corrected before changing the
lower plate.

g)        Horizontal plate readings and reduced angles can be recorded in a standard field book.

Note the different initial plate settings for each round, the use of the remarks column and the summary of angles.

The operation of one second theodolites is practically the same as that outlined above.  The only difference occurs during the initial sighting of the left hand target.

Sight the target first and then set the required plate reading.

Measurement of vertical angles

Vertical angles are useful in applying slope corrections to distance measurement and for determining reduced levels of inaccessible points.

The observing procedure is practically the same for all theodolites.

a)      Sight the target with the horizontal cross wire.

b)      Level the altitude bubble, unless the instrument has automatic vertical indexing in which case there may be a release button to press

c)      After adjusting the micrometer note the plate reading.

d)      Change face and repeat

The orientation of the vertical circle varies from one instrument to another and several examples are in Figure 6.  Study your theodolite carefully as it is
necessary to reduce vertical angles.

Lesson Note On theodolite - Levelling Methods Part B

Levelling

The theodolite could be used for leveling provided a number of precautions are taken.

a) The altitude bubble should be centred and the telescope locked with a vertical angle of exactly 00-00-00,

b) Read the staff.

a) Change face and repeat the above steps

b) The mean of the two staff readings will give a reasonable result over short distances.

Levelling by theodolite must never be regarded as an acceptable alternative to the surveyor’s level where accuracy is needed.

Optical distance measurement

Horizontal distances can be measured using theodolite and leveling staff.  These distances can be accurate to 0.1 m and cannot be used where accuracy is

required.

4              Sight a vertically held leveling staff and read the staff where it is cut by the horizontal crosswire and the two stadia hairs.

5              Check the staff readings.  The difference between center and top readings should equal difference between centre and bottom readings.  Read the staff again if there is a disagreement.

6              Note the vertical angle after levelling the altitude bubble.

7              Compute the horizontal distance from

100 xsxcos2  vertical angle

where s= difference between top and bottom stadia readings

Lesson Note On Surveying with GNSS (GPS and GLONASS)

Surveying with GNSS (GPS and GLONASS)

GNSS surveys use the signals transmitted by satellites with trajectories such that any point on the Earth’s surface can be determined around the clock and independent of weather conditions. The positioning accuracy depends on the type of GNSS receiver, and on the observation and processing techniques used.

The GNSS Advantage

What is the advantage of GNSS? Compared with the use of a total station, GNSS surveying offers the advantage that the points to be measured do not have to be mutually visible. Provided that the sky is relatively unobstructed (by trees, buildings, etc.) and adequate satellite signals can be received, GNSS equipment can be applied to many survey tasks that were traditionally carried out using electronic total stations.

Many GNSS systems today enable a diverse range of survey tasks with user-guided onboard applications to be carried out with centimeter accuracy in real-time kinematic (RTK) or post-processed on a tripod, pole, ship, vehicle, or on agricultural and construction machinery.

GNSS Reference Stations

Also known as a Continuously Operating Reference Station (CORS), a GNSS reference station is typically a multi-frequency GNSS receiver located at known coordinates, supplied with permanent power, and connected to several communication devices.

A CORS typically logs GNSS data for use in post-processing tasks or supplies real-time GNSS correction data to DGPS and/or RTK applications.

In many cases, it performs both tasks, satisfying the demands of many different applications, including surveying, engineering, construction, geodetic control, GIS, monitoring, tectonic studies, and hydrography.

Lesson Note On How to Stake Out Points and Profile Boards With a Total Station

How to Stake Out Points and Profile Boards With a Total Station

To create an as-built plan, the position and height of points are determined by measuring angles and distances. To do this, set your instrument up on any prominent point to create a local coordinate system.

Enter the coordinates as (X=0, Y=0, instrument height). Select a second prominent point for the purposes of orientation. After this has been targeted, the horizontal circle should be set to zero.

If a coordinate system already exists, set up the instrument on a known point within it and set the horizontal circle to a second known point.

Staking Out Points

1. Set up the instrument at a known point and set the horizontal circle.
2. Enter the coordinates of the point to be staked out. (The program automatically calculates direction and distance to the point – the two parameters needed for staking out.)
3. Turn the total station until the horizontal circle reads zero.
4. Position the reflector at this point (point P).
5. Measure the distance. (The difference in the distance D to the point P will be displayed automatically.)

The coordinates of the points to be staked out can be transferred beforehand from your computer to the total station. Under these circumstances, you only need to select the point number. If two points are known, you can also use the resection method to set up and orient your instrument.

Staking Out Profile Boards

In the example below, profile boards are to be erected parallel to the proposed walls of a large building and at distances of A and B, respectively, from the boundaries.

1. Establish a baseline AB parallel to the left-hand boundary and at a freely selectable distance C.
2. Mark point A at the defined distance D from the upper boundary. It will be the first location for the total station.
3. Using a ranging pole, mark point B at the end of the baseline.
4. Set up the total station on point A, target point B, and set out the points A1, A2, and A3 in this alignment in accordance with the planned length of the side of the building.
5. With point B sighted, set the horizontal circle to zero, turn the total station by 90° and set out the second line AC with the points A4, A5, and A6.
6. 
7. Some total stations, such as the Leica FlexLine series, have a Reference Line application. This application allows you to complete all of the above steps more efficiently and conveniently, and is the easiest way to stake out profile boards. In most cases, only one instrument setup is required.

Lesson Note On Role of GIS

Role of GIS

Geographic Information System (GIS) is rooted in intellectual practices, populated by data and powered by mathematical analysis. A survey conducted by Schuurman (2004) suggested that currently, the main use of GIS is for spatial analysis, predictive modelling, cartography and visualisation. The SI Industry, also known as the GIS industry, is a rapidly growing industry.  GIS maps the exact location and survey coordinates of an object in space to provide answer to queries using a computer system (Ibid, 2004).  

Furthermore, Monroe County (2008) defines the GIS as a mapping tool for mapping visualisation and geographic analysis.

1.       “Geographic Information Systems are computer based tools for mapping and analysing features and events on earth.  GIS technology integrates common database operations such as query and statistical analysis with the unique visualisation and geographic analysis benefits offered by maps” (Monroe County, 2008).

Thus, the use of GIS is needed to collect data, store, manage, analyse and produce useful information.  In other words, the process of GIS is to input sets of raw data to produce useful output information.  CAS relies on the input of accurate historical records and utilises the functionality of GIS to produce predictions and response plans for this natural phenomena.

Despite the vast potential applications of GIS, the means of integrating the pervasive role and influence of the technology have not kept pace with the current developments and techniques.  Put more simply, the use of GIS has not reached its potential because users are unaware of the possibilities for an integrated GIS in situations where spatial location is involved.  

As a result, this project will use the collection of datasets and integration from different sources to produce useful information for cyclone analysis study.  For this reason, the data acquisition process needs to be of a substantial quality and cover a range of datasets in order to produce meaningful results (Schuurman, 2004).  This is because GIS are dependent on spatial data, with poor quality data producing potentially invalid results (Ibid, 2004).

“The qualities of the data that populate data models constitute the best indicator of the quality of the resulting spatial analysis.  Poor quality or inappropriate data can invalidate the results of the analysis” (Ibid, 2004).

A function of GIS is the ability to query databases using a selection of attributes or selection of locations for special criteria to find the relationships between different results, as shown in Table 2.1.  Hence, GIS draw upon analysis models in the quantitative method.  Therefore, spatial analysis for the project requires the understanding of quantitative data calculations in order to create meaningful implementation.

Initial use of GIS was for cartography and mapping.  However, the methods of computerising cartographic procedures were coincident with the realisation that mapping could be used in analysis through overlays and calculations (Schuurman, 2004).  Nowadays, the analytical technique in GIS is known as spatial analysis,

1.       “Spatial analysis is differentiated from ‘mapping’ because it generates more information or knowledge that can be gleaned from maps or data alone” (Ibid, 2004).

Spatial analysis involves the overlapping of different characteristics of datasets, known as map overlays.  Map overlay, as illustrated in Figure 2.1, made up of collections of similar geographic objects, also known as features, arranged in layers.  It is through the overlay technique, that the result of the analysis can be understood, for example Monroe County (2008).  Every feature in a GIS map is connected to a spatial table in the overlay.  The table is filled with attributes of data that could be examined as information (Ibid, 2008).

Furthermore, GIS divides the world into objects and attribute tables, both of which can be represented spatially by raster or vector datasets which are shown on the map overlay:

1.•Raster dataset that comes from grids, e.g. images, aerial photos.

2.•Vector dataset that comes from mathematical calculations and functions, e.g. points, lines, polygons.

Both types of dataset will be used to produce complete and extensive data in the Area of Study.  

GIS also has programming capabilities, however, in this thesis the programming is limited to simple queries in SQL and VB languages, for example ArcObjects.  As a result, simple map algebra and

Figure 2.1 - Data and Information comes from a set of layers (ESRI, 2008; Geoscience Australia, 2008).

calculation functions can be achieved.  Therefore, the main tool for CAS involves visualisation and analysis using GIS.  

For this reason, the CAS is associated with SI because of the diverse type of applications possible.  In addition, CRC SI (2008) defines the use of SI for the Australian community is necessary to the community, especially when maps of all kinds are produced, displayed and analysed using technology that the wider spatial information industry provides.

This is also evident when Schuurman (2004) points out that the challenges are associated not only for visualisation and analysis, rather with modelling spatial phenomena using GIS. 

1.        “Spatial analysis and modelling are increasingly used to predict outcomes, and plan for future development or natural hazard.  The capacity of GIS have been extended from managing data and map distribution to model interactions among different attributes of the spatial objects and use the information to predict future events” (Ibid, 2004).

As a result, SI holds such importance because of various forms of GIS functionality, for example enquires, integrates, manages, analyses, maps, distributes, and uses geographic, temporal and spatial information and knowledge.  Hence, it is important for the system to provide adequate planning, decision-making and operational needs of people and organisations of all types (CRC SI, 2008).

In particular, ArcGIS Desktop software from ESRI has been chosen for the course of this thesis because, 

1.       “ArcGIS is full featured geographic information system (GIS) software for visualising, managing, creating and analysing geographic data.  Using ArcView, you can understand the geographic context of your data, allowing you to see relationships and identify patterns in new ways” (ESRI, 2008)

In other words, ArcGIS is a GIS enterprise developed and maintained by ESRI.  For the course of this project, the desktop GIS platform is used to produce spatial analysis, visualisation and cartography, and spatial data management.  Additionally, the software could be used for authoring, serving, and using geographic information.  

Furthermore, ESRI (2008) details features of the ArcGIS 9.2 Suite, which is the version released since the start of the thesis, that are applicable to the CAS such as:

1. •Quality mapping for the study area base maps

2. •Spatial Analysis for socio economic and population data

3. •Data Use and Integration of Australian Bureau of Statistics datasets

4. •Data Query and Exploration of PSMA LGA datasets

5. •GIS Deployment of the evacuation system

6. •Map Viewing and Navigation for the evacuation maps

7. •Map printing for all key maps 

8. •Configurable and Customisable for future studies

Additionally, it is the most widely used software in industry, with superior features to its closest counterpart, as shown in Figure 2.2.  Perhaps due to its functionality and spatial analysis it would justify the use of ESRI software platform.

Figure 2.2 – GIS users

(Directions Magazine, 2003)

For this reason, ArcGIS 9.2 is the main component for this project, used as the platform in the framework because of its capability to create, manage, publish and disseminate the GIS knowledge for all the society (ESRI, 2008).  GIS is the main core of this project that will be used as a tool to integrate Cyclones and its spatial analysis for the visual representation of the study area.  

Since the study will be focussed on GIS, Table 2.2 shows the types of activities that will be undertaken using GIS.

LESSON NOTE ON HOW A GIS WORKS

HOW A GIS WORKS

 A GIS stores information about the world as a collection of thematic layers that can be linked together by geography. This simple but extremely powerful and versatile concept has proven invaluable for solving many real-world problems from modeling global atmospheric circulation, to predicting rural land use, and monitoring changes in rainforest ecosystems.

GEOGRAPHIC REFERENCES

Geographic information contains either an explicit geographic reference such as a latitude and longitude or national grid coordinate, or an implicit reference such as an address, postal code, census tract name, forest stand identifier, or road name. An automated process called geocoding is used to create explicit geographic references (multiple locations) from implicit references (descriptions such as addresses). These geographic references can then be used to locate features, such as a business or forest stand, and events, such as an earthquake, on the Earth's surface for analysis.

GIS TASKS

 General purpose GIS’s perform seven tasks.

• Input of data

• Map making

• Manipulation of data

• File management

• Query and analysis

• Visualization of results

Input of Data

 Before geographic data can be used in a GIS, the data must be converted into a suitable digital format. The process of converting data from paper maps or aerial photographs into computer files is called digitizing. Modern GIS technology can automate this process fully for large projects using scanning technology; smaller jobs may require some manual digitizing which requires the use of a digitizing table.

Today many types of geographic data already exist in GIS-compatible formats. These data can be loaded directly into a GIS.

Map Making

 Maps have a special place in GIS. The process of making maps with GIS is much more flexible than are traditional manual or automated cartography approaches. It begins with database creation. Existing paper maps can be digitized and computer-compatible information can be translated into the GIS. The GIS-based cartographic database can be both continuous and scale free. Map products can then be created centered on any location, at any scale, and showing selected information symbolized effectively to highlight specific characteristics.

The characteristics of atlases and map series can be encoded in computer programs and compared with the database at final production time. Digital products for use in other GIS’s can also be derived by simply copying data from the database. In a large organization, topographic databases can be used as reference frameworks by other departments.

Manipulation of Data

For small GIS projects it may be sufficient to store geographic information as simple files. There comes a point, however, when data volumes become large and the number of data users becomes more than a few, that it is best to use a database management system (DBMS) to help store, organize, and manage data. A DBMS is nothing more than computer software for managing a database--an integrated collection of data.

There are many different designs of DBMS’s, but in GIS the relational design has been the most useful. In the relational design, data are stored conceptually as a collection of tables. Common fields in different tables are used to link them together. This simple design has been widely used, primarily because of its flexibility and very wide deployment in applications both within and without GIS.

Query and Analysis Once you have a functioning GIS containing your geographic information, you can begin to ask simple questions such as

• How far is it between two places?

• How is this particular parcel of land being used?

 • What is the dominant soil type for oak forest?

• Where are all the sites suitable for relocating an endangered species?

• Where are all of the sites possessing certain characteristics?

• If I build a new highway here, how will animals in the area be affected?

GIS provides both simple point-and-click query capabilities and sophisticated analysis tools to provide timely information to managers and analysts alike. GIS technology really comes into its own when used to analyze geographic data to look for patterns and trends, and to undertake "what if" scenarios.

Modern GIS’s have many powerful analytical tools, but two are especially important. Proximity Analysis is used to examine spatial relationships by determining the proximity relationship between features.

Overlay Analysis integrates different data layers to look for patterns and relationships. At its simplest, this could be a visual operation, but analytical operations require one or more data layers to be joined physically. For example, to analyze the impact of urbanization on ecological characteristics of an area, an overlay could integrate data on soils, hydrology, slope, vegetation, and land use. Queries could be used to identify sources of pollution, to delineate potentially sensitive areas, or to plan for increased population growth in the area.

Visualization

For many types of geographic operations, the end result is best visualized as a map or graph. Maps are very efficient at storing and communicating geographic information. While cartographers have created maps for millennia, GIS provides new and exciting tools to extend the art and science of cartography. Map displays can be integrated with reports, three-dimensional views, photographic images, and with multimedia.

LESSON NOTE ON COMPONENTS OF A GEOGRAPHIC INFORMATION SYSTEM

COMPONENTS OF A GEOGRAPHIC INFORMATION SYSTEM

A working Geographic Information System seamlessly integrates five key components: hardware, software, data, people, and methods.

 H A R D W A R E

Hardware includes the computer on which a GIS operates, the monitor on which results are displayed, and a printer for making hard copies of the results. Today, GIS software runs on a wide range of hardware types, from centralized computer servers to desktop computers used in stand-alone or networked configurations. The data files used in GIS are relatively large, so the computer must have a fast processing speed and a large hard drive capable of saving many files. Because a GIS outputs visual results, a large, high-resolution monitor and a high-quality printer are recommended.

S O F T W A R E

GIS software provides the functions and tools needed to store, analyze, and display geographic information. Key software components include tools for the input and manipulation of geographic information, a database management system (DBMS), tools that support geographic query, analysis, and visualization, and a graphical user interface (GUI) for easy access to tools. The industry leader is ARC/INFO, produced by Environmental Systems Research, Inc. The same company produces a more accessible product, ArcView, that is similar to ARCINFO in many ways.

D A T A

Possibly the most important component of a GIS is the data. A GIS will integrate spatial data with other data resources and can even use a database management system, used by most organizations to organize and maintain their data, to manage spatial data. There are three ways to obtain the data to be used in a GIS. Geographic data and related tabular data can be collected in-house or produced by digitizing images from aerial photographs or published maps. Data can also be purchased from commercial data provider. Finally, data can be obtained from the federal government at no cost.

P E O P L E

GIS users range from technical specialists who design and maintain the system to those who use it to help them perform their everyday work. The basic techniques of GIS are simple enough to master that even students in elementary schools are learning to use GIS. Because the technology is used in so many ways, experienced GIS users have a tremendous advantage in today’s job market.

M E T H O D S

 A successful GIS operates according to a well-designed plan and business rules, which are the models and operating practices unique to each organization.