MAPPING OF MALDIVES USING AERIAL PHOTOGRAPHY AND DIGITAL PHOTOGRAMMETRIC TECHNIQUES

V. Raghu Venkataraman*, K. Kalyanaraman, Dr. K. Radhakrishnan, Dr. R.R Navalgund, P. Srinivas*, PVSSN Gopalakrishna, CVKVP Jagannadha Rao, K. Srinivasa Rao, G. Srinivas, P. Shashivardhan Reddy, J. Narendran, CS Narsimham, Dr. K. Venugopala Rao.

AERIAL SERVICES & DIGITAL MAPPING AREA

National Remote Sensing Agency, Department of Space, Govt. of India,

Balanagar, Hyderabad – 500037, India

Corresponding author 1 - P. Srinivas

e-mail: srinivas_p@nrsa.gov.in

National Remote Sensing Agency,

Department of Space, Govt. of India,

Aerial Services & Digital Mapping Area,

Balanagar, Hyderabad – 500 037

Andhra Pradesh, INDIA

Telephone Nos. 0091 040 23884489 (O)

Fax No. 0091 040 23884483

Corresponding author 2 - V. Raghu Venkataraman

e-mail: raghu_vv@nrsa.gov.in

Telephone Nos. 0091 040 23884470/71 (O)

Abstract

Republic of Maldives is located in the Indian Ocean about 300 miles south of

India and 450 miles south west of Sri Lanka consisting of 26 atolls with 1192

islands scattered between 1º S to 8º N latitude, 72º E to 74º E longitude with 99

% of the area being water.

The objective of this project was to prepare digital maps of the entire country in

1:25,000 scale using aerial photographs acquired in 1:40,000 scale in a single

coordinate system. Remote sensing satellite data was acquired for preliminary

reconnaissance of the terrain and selection of reference and base stations for

continuous Global Positioning System (GPS) observations to establish reference

datum in WGS 84. Thereafter, flight operations for aerial photography were

carried out with automated Computer Controlled Navigation System (CCNS).

Digital photogrammetry techniques with Kinematic GPS data and pre pointed

GPS control survey data was utilized for aero triangulation, block adjustment and

vector capture.

The large scale mapping for 16 select islands of Maldives was carried out in

1:1000 scale using 1:6000 scale aerial photographs.

Keywords: Aero triangulation, Digital photogrammetry, GPS, Reference station,

CCNS.

1. INTRODUCTION

The Republic of Maldives consists of an archipelago of 1192 islands scattered

over a distance of 870 km in the North–South direction and about 150 km in the

East-West direction between 0º42’30”S to 7º6’30” N latitude, 72º32’30” E to

73º46’15” E longitude. It is located in the Indian Ocean about 480 km South of

India and 725 km South West of Sri Lanka.

The islands are grouped in the form of atolls. An atoll is a coral island consisting

of a circular belt of corals enclosing a central lagoon. Maldives consists of 26

atolls. The atolls and islands are scattered and spread across an area of 100 000

sq. km. area, 99% of which is water and less than 1% covers land portion. Only

33 islands have a land area of more than 1 sq. km and one third of all the

inhabited islands have fewer than 500 people.

Earlier, different organizations have attempted and prepared very small scale

maps for navigation but large scale maps of atolls and islands could not be

prepared due to non availability of appropriate technology. With the advent of

Global Positioning System (GPS) and photogrammetry techniques coupled with

stereo aerial photography the potential for digital mapping in a single reference

frame work was realized through a collaborative project between the Government

of India (GoI) and the Republic of Maldives.

This paper attempts to provide a comprehensive picture of the methodology,

technology and processes involved in the execution of the project by the National

Remote Sensing Agency (NRSA), Hyderabad an organ of the Department of

Space (DOS), GoI.

2. BACKGROUND

In 1999, Honorable Mr. Ibrahim Hussein Zaki, Minister for Planning and National

Development, Government of Maldives had discussions with the High

Commissioner of India, Hon’ble Mr. Kanwar Singh Jasrotia regarding the

possibility of digitally mapping the archipelago and establishing of a remote

sensing unit in his country. Thereafter the Maldivian authorities sent a request for

this purpose. The GoI responded to this request with a project proposal which

was shared with the Maldivian authorities.

The President of Maldives H.E. Mr. Maumoon Abdul Gayoom, during the state

visit to India in August, 2000, had evinced keen interest in the work carried out by

NRSA and requested follow up action on the above mentioned project proposal.

Based on the request from the Maldivian authorities, The Ministry of External

Affairs (MEA), GoI approached DOS and asked for a detailed project proposal for

consideration by both the Governments. Accordingly the project proposal was

prepared by NRSA for further consideration and implementation.

3. PROJECT OBJECTIVES

NRSA was awarded the project “Digital Mapping of The Republic of Maldives” by

the MEA. The project consisted of:

3.1 Preparation of digital maps on 1: 25 000 scale using 1: 40 000 scale aerial

photographs for entire Maldives in a single reference frame with Universal

Transverse Mercator (UTM) coordinates.

3.2 Preparation of digital maps on 1: 1 000 scale using 1: 6 000 scale aerial

photographs for 16 selected islands.

3.3 Establishment of a Remote Sensing Centre at Male, Maldives

4. AVAILABILITY OF MAPS

It was reported that metric charts of Maldives published in 1993 covering the

whole of Maldives on a scale of 1:300 000 were available as given below:

Maldives Sheet 1 : Addu Atoll to North Huvadhoo

Maldives Sheet 2 : North Huvadhoo Atoll to Mulaku Atoll

Maldives Sheet 3 : Mulaku Atoll to South Maalhosmadulu Atoll

Maldives Sheet 4: South Maalhosmadulu Atoll to Thavndhippothu Atoll.

These charts are the updated version using aerial photos taken by Royal Air

Force (RAF) of UK in 1968 and 1969 and satellite imagery acquired between

1984 and 1988. These 1:300 000 charts were of not much of use to for detailed

development planning as the Islands of Maldives are very small, ranging from 0.5

sq. km. to 2 sq. km. In addition, 8 sheets on 1:250 000 scale based on UTM

projection were also available, but these maps also lacked much of the required

details in terms of size and land area of the islands.

In the course of execution of this project, the 4th edition of the “Atlas of the

Maldives”, (ISBN 1 876410 42 6) published in 2004 by Atoll Editions, PO Box

113, Apollo Bay, Victoria, 3233, Australia was extensively used as a reference

document.

5. METHODOLOGY

The methodology for the preparation of digital maps (Paul R. Wolf and Bon A.

Dewitt) on 1:25 000 scale and 1:1 000 scale involved the following processes as

indicated in Fig. 1 and Fig. 2 respectively.

5.1 Flight planning of aerial photography operations.

5.2Aerial Photography in 1: 40 000 scale and 1: 6 000 scale (for few selected

islands) with Kinematic GPS (KGPS) observation

5.3GPS observations on Reference stations (13 Nos.) and pre-targets (41

Nos.) of size 5m x 5m for establishment of reference frame in WGS 84

datum for entire Maldives

5.4Processing of aerial exposed film rolls & annotations of processed film rolls at

Photo processing lab at NRSA.

5.5Ground control survey for few selected islands on 1: 6 000 aerial photographs

5.6Post processing of airborne Kinematic GPS data and static GPS reference

stations and other ground control points.

5.7Scanning of aerial film rolls using precision photogrammetric scanner @ 21

microns for 1: 40 000 scale aerial photographs and @ 20 microns for 1: 6

000 scale aerial photographs.

5.8Aero triangulation (densification of ground control points) using softcopy /

Digital Photogrammetry systems.

5.9Digital Mapping on 1: 25 000 / 1: 1 000 scale using Photogrammetry systems

for plotting and subsequent use in Geographic Information System (GIS)

environment.

5.10 Field verification / data collection for few selected islands and other atolls

on 1: 1 000 scale and 1: 25 000 scale map sheets respectively.

5.11 Quality control of digital maps

6. RATIONALE FOR METHODOLOGY FOR 1:25 000 SCALE MAPS

The methodology for mapping in 1:25 000 scale was arrived at based on the

required map content and need to have a country wide coordinate system.

6.1 Requirements

The most challenging requirement was of course the need to have a single grid

coordinate system for the entire country.

As regards content, essentially the 1:25 000 scale maps had to show the extent

of the land area in terms of both shape and size clearly demarcating the land and

water boundary, atolls, built up areas, roads, and vegetation.

As regards coordinates and projection, the need was to accurately depict the

position of the islands in the country wide grid. This would automatically give the

positions of the islands relative to each other and the distances between them.

6.2 Data sources

B & W stereo aerial photography in 1:40 000 scale was selected as the primary

data source because it would provide a spatial resolution of about 100 cm which

is adequate for demarcating the required content layers. The option of utilizing

high resolution satellite data with 100 cm resolution was also thought of but

discarded since the data comprising of about 800 scenes of entire 100 000

square km area would have to be sourced as the frame sizes are normally of 10

km x 10 km size. Aerial photography provided the twin advantage of economic

and selective data acquisition covering only those areas where the proportion of

land was significant as well as providing stereo data for generation of height

information. RMK 15/23 camera was selected as it would provide metric quality

photographs with wide swath to reduce overall flying time.

For the purposes reconnaissance for aerial photography and GPS based control

survey, LISS III sensor imagery of IRS 1C-1D was selected as the imagery with a

resolution of 23 m and in color clearly show the relative positions of the islands

along with the shape and size of the islands.

Since it would be virtually impossible to get required controls using traditional

methods due to the vast expanses of water the only option was to use GPS

controls. The GPS points were pre-signalized so as to be able to be identified on

the aerial photos.

To derive full benefit of the availability of Kinematic GPS data for the aircraft

platform for initial estimation of the frame centre coordinates.

6.3 Data processing and mapping

Since the primary data was on film it was decided to convert it to digital form

using high quality photogrammetric scanner.

It was also decided to utilize digital photogrammetrc techniques for aero

triangulation and block adjustment since analytical systems were obsolete and a

certain level of automation was inherently available for point selection.

Once the primary data is oriented in such to the correct direction and block

adjustment completed, the process of vector capture in the mapping

environment, comprising of PC based low cost systems, was selected for yielding

the line maps with appropriate symbols so that multiple systems could be

deployed.

7. RATIONALE FOR METHODOLOGY FOR 1:1 000 SCALE MAPS

7.1 Requirements

The main requirement was content. 1:1 000 scale maps had to show each

individual building and built up features very clearly along with the land area

utilized and the distances between features have to be accurate within 25 cm

besides the extent of the land area in terms of both shape and size.

7.2 Data sources

B & W stereo aerial photography in 1:6 000 scale was selected as the primary

data source because it would provide a spatial resolution of better than 10 cm

which is adequate for demarcating the required content layers. Stereo data was

critical for accurately mapping buildings.

To derive full benefit of the availability of Kinematic GPS data for the aircraft

platform for initial estimation of the frame centre coordinates.

7.3 Data processing and mapping

Since the primary data was on film it was decided to convert it to digital form

using high quality photogrammetric scanner.

It was also decided to utilize digital photogrammetric techniques for aero

triangulation and block adjustment since analytical systems were obsolete and a

certain level of automation was inherently available for point selection.

8. FLIGHT PLANNING

Flight planning was an important and critical component for this project since

most of the area is covered by water. Information from various sources such as

satellite images, existing atlas maps of Maldives, old maps etc., was used to

prepare optimized flight plans so as to make flying economical and minimize

wastage of both flying time and aerial film. This was especially critical as the

window of opportunity comprising of cloud free season over the area is extremely

limited. The imagery from LISS-III sensor of Indian Remote Sensing Satellites

(IRS 1C/1D) for the entire area was used for preliminary reconnaissance and

flight planning. The above IRS imagery were also utilized for identification of

suitable locations for the GPS reference stations and Ground Control Point

(GCP) pre signalized targets in an economical manner. The World Wide Mission

Planning (WWMP) software was used for flight planning.

The entire country was divided into seven geographical blocks for planning,

managing and execution of the project as shown in Fig. 3 for aerial photography

in 1: 40 000 scale. The runs were planned for some blocks in N-S direction and

for some blocks in E-W direction depending on the shape of the block. Besides

the main runs, tie lines were also planned for each block in oblique direction.

Since the land portion was less the number of tie lines planned was much more

than in normal situations. The intersection of main lines and tie lines in the flight

plan was made in such a way as to fall in as many islands as possible.

The details of the flight plans are given below in Table 1

9. AERIAL PHOTOGRAPHY OPERATIONS

Aerial photography (Black & White) was carried out using Beech Super King Air

B-200 (Fig. 4) mounted with Zeiss RMK15/23 metric camera and integrated with

INS and Kinematic GPS. The aircraft is guided by Computer Controlled

Navigation System (CCNS) software for carrying out aerial photography very

accurately. The camera is tightly coupled with CCNS that in turn connected to

airborne GPS.

After interactive checks and corrections of the software-generated flight lines, the

data is stored on a PCMCIA card. The aircrew was also provided with this flight

planning information in hard copy form. During aerial photography this data is

transferred to the on board computer. The aircraft navigation is carried out with

the assistance of CCNS4, which is supported by GPS a satellite navigation

system. At the precise moment that an aerial photo is exposed, the position of

the aircraft can be determined by evaluating the signals from, at a minimum, four

satellites. In addition to computer controlled navigation, aircraft position at the

precise moment of shutter release can be determined by a ground station using

Kinematic GPS (KGPS). After completion of aerial photography, the recorded co-

ordinates of the camera’s projection centres are read into Bentley’s MicroStation

CAD software using a standard interface and then plotted out as flight line

indices.

The CCNS is a guidance, positioning and management system for aerial survey

flight missions. The basic system consists of the Central Computer Unit (CCU),

the 5'' TFT Command and Display Unit (CDU), and necessary cabling and

mounting. Optional equipment completes the system to fulfill specific

requirements. The system is universally usable and can operate and integrate all

Wild/Leica, Zeiss respectively. Z/I Imaging aerial camera systems. It provides a

complete and comprehensive solution for mission planning and documentation,

aircraft guidance and sensor management during missions. CCNS controls the

camera and other sensors, including crab/drift setting(s), forward overlap, V/H

computation and provides data for data annotation on film; the co-ordinates may

be WGS84 or the countries X/Y co-ordinates (optional).

The CCNS brings the advantages of a glass cockpit and a fully automated flight

control system to aerial surveying and reconnaissance. All operations are

activated via one knob and four buttons. The EFIS type display, which is

operated like an aircraft instrument, is divided into guidance and system/sensor

management information (right side of the display). The pilot just has to "follow

the needle". Outputs, with selectable sensitivity for HSI, VDI and CDI

instruments, are provided.

The camera used in this project is RMK aerial survey camera System. It features

a systematic, modular design with individual components forming logical

functional units optimized for both practical application and economical use. The

RMK features high-performance lenses with internal filters, which significantly

enhance image quality and a unique pulsed rotating-dish shutter. It is Ideal for

GPS/INS - supported navigation and aero triangulation. It also has eight point-

shaped fiducials in the corners and midway along the edges, numbered 1 to 8,

spacing 113 mm, point diameter 100 µm, cross lines with 50 µm line thickness,

exposed at midpoint of exposure.

The flight operations were carried out during the month of February, 2004 as that

was the ideal cloud free season over Maldives. Aircraft was ferried from

Hyderabad to Male via Trivandrum. Permission from the Director General of Civil

Aviation (DGCA), GoI was taken prior to departure as per the regulations for ferry

flight to Male without licensed Navigator and for YA number was YA/N

538/01/30094. Civil Aviation Department of Maldives issued clearance letter to

Maldives airports authorities for entry into Maldivian airspace vide Permit no. is

CAD-VRMM/LP-IEXT/04/32.

The aircraft was mobilized only with crew, maintenance engineers, equipment

and film. Camera system engineers, GPS survey team and coordinators were

mobilized via civil airlines.

After the flight planning was completed hard copy print outs were taken for

reference. Two PCMC cards with flight planning data were provided for loading

on to the aircraft CCNS which was loaded and checked prior to departure.

Aircraft readiness was also checked at the base. The SKA B-200 aircraft has a

mandatory 100 hour inspection to be carried out at base with hanger and stores

facility. The volume of flying effort involved in terms of flying time was carefully

estimated including main ferry, local ferry, actual operations and alignment/ turn

times. This was optimized to approximately 95 hours by avoiding water areas so

that the aircraft could mobilize to Maldives after 100 hour inspection at

Hyderabad and complete the entire task without having to interrupt for coming

base to base for inspection. To ensure snag free performance spare tyres and

A total of 25 film rolls of 240 mm format each having a capacity of exposing 275

frames was drawn from the refrigerated stores and loaded into the aircraft for

mobilization. At Male the film rolls were unloaded and kept in a safe custody in

air-conditioned environment to prevent degradation of film due to heat.

Aerial photography operations were carried out from Male international airport as

the base. Sorties were carried out in such a manner that the local ferries were

made productive for tie lines.

10. GPS SURVEYS

10.1 Reference stations

Thirteen GPS reference stations spread over the entire Republic of Maldives in

different blocks for the project were used for airborne GPS assisted aerial

photography for the establishment of reference network (Sapporo, July 2003 &

Tomas Soler, Lucy W.Hall and Catherine K. Reed., 1998) in WGS-84 and pre-

target GCPs in tandem as shown in Table 2. The reference stations were located

in such a way that at least one reference station was there in one-degree grid.

Each reference station was occupied with geodetic grade dual frequency GPS

receivers for a minimum of three days for duration of 12 hours from 6 AM to 6 PM

every day. The Male International GNSS Services (IGS) station was also

occupied as part of this GPS campaign. A permanent monument was established

at each reference station site.

10.2 Pre-target base stations

Forty two pre-target GCPs spread over the entire country were installed in place

and GPS survey of the points was carried out as shown in Table 3. The pre-

target GCP designed was 5m X 5m in dimension with plus mark in white and

remaining quadrant area in black as shown in the Fig. 5. Each pre-target GCP

was occupied continuously with a geodetic grade GPS receiver for duration of 3

hours simultaneously with the GPS reference station as shown in the Fig. 6.

The land area of Republic of Maldives is spread over 100 000 Sq. Km. The

planning of aerial photography, deployment of personnel for reference station

operations and pre target surveys involves meticulous planning, coordination

and implementation of the plan. Most of the islands in Maldives are uninhabited

and locating natural and man-made features are next to impossible, hence pre

signalization was carried out before the aerial photography. The major portion of

the country is covered with water and the numbers of airports were less, hence

deployment of personnel at different GPS locations by traveling very long

distance on open sea was an Herculean task. The following map as shown in the

Fig. 7 depicts the planning carried out in the deployment of the personnel at

different GPS sites.

10.3 GPS Data processing

The GPS data pertaining to the reference station is processed in a Bernese

scientific post processing software, which is capable of processing long baselines

and the coordinates of the reference stations are computed using the GPS data

from the nearest IGS stations namely Bangalore (India), De Garcia (Indian

Ocean), NTUS (Singapore), Bahrain etc. The coordinates of Pre-targets was

derived by processing the GPS data collected at Pre-targets with reference to the

nearest reference stations using SKIPRO software in differential mode.

11. PATH RECOVERY, SCANNING OF AERIAL PHOTOGRAPHS, AERO TRIANGULATION AND BLOCK ADJUSTMENT

The path recovery of aerial photographs was a Herculean task. It involved

retrieving the aerial photos as per the planned flight plans and recee reports

(prepared by pilots on the day of aerial photography). Since 99% of the entire

Republic of Maldives is covered with water, identifying and segregating of aerial

photographs as per the recee report and flight plans was a very difficult task. This

was very important to reduce the volume of effort in scanning of the aerial

photographs.

The scanning of aerial photographs was carried out using very high precision

Zeiss SCAI Photogrammetry scanner and aerial photographs in 1: 40 000 scale

were scanned at 21 microns. The scanning was executed very carefully by

applying enhancements since the terrain was very difficult and sun light was

varying from one part of the atoll to another. The pre-targets placed on the

ground were identified as shown in Fig. 8 and checked with the flight plan. Thus

only 2377 out of the total 4456 frames representing 53 % of the frames were

scanned. At an average daily productivity of 20 frames per day, this optimization

resulted in saving about 100 days in the time schedule. These digital images

were used for automatic aerial triangulation and block adjustment.

Triangulation is defined as the extension or densification of control within the

block. Block adjustment depends on the distribution of GCPs, quality of GCP,

type of terrain, quality of image (for generation of tie points by image matching)

and the proper analysis of the block. The sigma defines the accuracy of the block

The scanned aerial images were input to the aero triangulation along with

camera calibration report, processed DGPS data and processed KGPS data.

Triangulation was carried out using high-end Photogrammetry system consisting

of Socetset software along with Orima block adjustment software. Automatic aero

triangulation with an autonomous batch process by selecting pre-selected tie

points and appropriate matching strategy was used in this project. Aero

triangulation was performed with different strips composed of both parallel and

cross strips covering seven blocks. Utilization of Digital Photogrammetry Work

Station (DPWS) with automation in triangulation and bundle block adjustment

had reduced the processing time and expensive manpower otherwise required

for analytical aerial triangulation. The project file was set up in Socetset with all

the scanned images and calibration parameters such as calibrated focal length,

fiducial mark coordinates, Principle Point coordinates, radial distortions etc.

Automatic IO was carried out in batch mode by image correlation with the fiducial

templates available for RMKTOP camera.

The use of GPS derived antenna positions during the photo acquisition had

considerably improved the performance of the aerial triangulation process as well

as reduced the number amount of ground control points in the field (C.S.Fraser,

1994). Since the land portion is 1% of the total extent of the Maldives, enough

GCPs (pre-targets) could not be placed. The exposure coordinates of each frame

was taken as primary control and given more weight age for the block adjustment

as compared to the Pre-target GCPs. The ground control points used for the

block adjustment were the pre-targets, reference stations and processed KGPS

data.

The other inputs for this project such as camera calibration file, flight plan index,

overlaps, image scale and image sequences were used for initial approximation

of the block. GPS camera stations are used for the stabilization of the block. The

results of block adjustment are based on the average image precision

measurement of 0.5 to 1 pixel.

The triangulation of aerial photographs in 1: 40 000 scale was carried out for

individual blocks as shown in the Fig. 3. However for aerial photographs in 1:

6000 scale, the triangulation was carried out island wise and adjusted

accordingly. The GCPs were acquired by our team for selected islands in the

difficult terrain conditions. The nearest reference station was taken as the base

station and the GPS survey was carried out in the same coordinate system

reference schema. The results of aerial triangulation for all the blocks are

tabulated as shown in the Table 4.

12. REFERENCE GRID

A reference grid has been designed for covering the entire Maldives with 1:25

000 scale maps. The reference grid is in UTM projection. The grids are of 10 000

m (10 km) interval. The Latitude and Longitude values are also available in

Degrees, Minutes & Seconds for which the gridlines are drawn for 1 degree, 15

minutes and 7 ½ minutes intervals.

The numbering schema for the entire Maldives on 1: 250 000, 1: 50 000 and 1:

25 000 scale maps are shown in Fig. 9, Fig. 10 & Fig. 11 respectively. The

numbering schema derived for 1: 25 000 scale maps is as per the International

Map World (IMW) series. In Maldives most of the area is in northern hemisphere

above the equator and a small portion part of the area falls in southern

Hemisphere, below the equator. To have positive coordinate value in North

direction, the origin was shifted to the Southern Hemisphere. The zone number

43 (Southern hemisphere) was taken for processing the GPS coordinates with

UTM projection. The datum (vertical reference) for the mapping is with respect to

WGS 84.

13. LAYER LIST

The data is captured in different layers as per the feature (layer list), which aides

in importing the data into GIS environment. The list of maps in 1:25 000 which

actually cover land or atoll portion (no deep waters) is as given below as shown

in Table 5. List of islands for which 1:1 000 scale maps were prepared and are

listed below in Table 6. The layer list used for the preparation of maps in 1: 25

000 scale for entire Republic of Maldives & 1: 1 000 scale for selected islands

are listed in the Table 7.

14. GIS DATABASE

Maldives GIS database has been created at 1:1 000 scale and 1:25 000 scale

using object oriented technology with open GIS standards in ArcGIS

environment. In order to have compatibility with base maps in AutoCAD format,

the GIS data models were developed with same spatial reference system

including datum, projection and spatial extent.

To facilitate nation wise as well for island wise GIS applications such as censes,

utilities (water supply, sewerage, gas, communication, power, environmental,

agriculture, fisheries, navigation, national security, transportation) and revenue a

seam less GIS data model was developed.

Keeping GIS database volume and optimization, it is proposed to develop the

data structures as personal GIS geodatabase, which uses the Microsoft access

to store the both spatial and non-spatial database. The developed GIS database

can be scalable to enterprise GIS database using Relational Data Base

Management (RDBM) software like oracle, once the GIS applications developed

over this as mentioned above.

15. ESTABLISHMENT OF REMOTE SENSING LAB AT MALE

The establishment of Remote Sensing Centre at Male, Maldives involved the

following:

15.1 Procurement of digital image processing system, digital photogrammetry

system, GPS receivers & GIS system. All the hardware and software

modules were tested at NRSA.

15.2 Training of personnel of Maldives for the period of 4 to 6 weeks at NRSA.

This phase of training was carried out in November / December 2004 for 4

Maldivian officials

15.3 Submission of digital maps. The final maps including orientation files,

images etc has been copied in the systems at Maldives and NRSA

officials had demonstrated the usage of the maps for different

applications.

15.4 Installation of systems at the full fledged remote sensing unit with all the

hardware and the software as shown in Table 8 at Male, Republic of

Maldives during April 2006 with on site training on the systems with the

populated with digital maps.

16. CONCLUSIONS

The aerial photography along with the establishment of reference datum in WGS-

84 was carried out for the first time for entire Republic of Maldives. Mapping in 1:

25 000 scale for entire Maldives and large scale mapping in 1: 1000 scale for a

few selected islands are the landmark. The whole task including the

establishment of remote sensing centre at Male was completed within the

stipulated project time as planned and the timeline for the individual activities is

as shown in Fig. 12.

17. ACKNOWLEDGEMENTS

We acknowledge our sincere thanks to the DOS, GoI for giving us the

opportunity to take up this project. We also acknowledge our thanks to MEA for

funding and awarding the project to DOS.

We extend our sincere thanks to Dr. RR Navalgund, Director SAC who had

extended his full support in planning and executing the project in his capacity as

Director, NRSA. We also extend our warm thanks to Director, NRSA Dr. K.

Radhakrishnan for his guidance in establishing a remote sensing centre at Male,

Maldives.

We acknowledge the contribution of all the other personnel involved in the project

mainly (i) pilots Capt. AL Hannurkar and Capt SMH Mehdi, (ii) Navigator Wg.

Cdr. (retd) Dalbir Singh, (iii) Aircrew engineers, field survey personnel and

photogrammetrists Shri B. Laxman, Mrs. I Jayalakshmi, Shri P. Krishnaiah, Shri

B. Sadasiva Rao, Shri Anantha Padmanabha, Shri M. Sreedhar, Shri NMS

Reddy, Shri D. Syama Rao, Shri G. Anil Kumar, Shri Y. Srinivasa Rao, Mrs. M.

Udayalakshmi, Mrs. TE Rani, Shri P. Srinivas Reddy, Shri G. Devender Rao, Shri

K. Krishna and Shri Ashutosh Bharadwaj.

18. REFERENCES

Paul R. Wolf and Bon A. Dewitt, Elements of Photogrammetry

Sapporo, The Royal Thai Survey Department - A report on the Geodetic

work (1999 – 2002) at the XXIII General Assembly of the International

Union of Geodesy and Geophysics during 30 June – 11 July, 2003.

Tomas Soler, Lucy W.Hall and Catherine K. Reed., 1998, -

Establishment of a GPS High accuracy Reference Geodetic Network in

the Caribbean, Surveying and Land Information System, Vol. 58, No. 1,

1998, pp 13-24.

C.S.Fraser, - GPS Aerotriangulation – in sights from Angledool project.,

Aust .j.Geod. Photogram.Surv, No.61, December, 1994, pp 1 – 16.

List of Tables

Table 1: Flight Plan Details for 1:40 000 scale photography

Table 2: GPS Reference Station for Airborne GPS

Table 3: GPS Reference & Target / Rover Stations

Table 4: Results of Aerotriangulation of entire Maldives shown as blockwise

Table 5: List of maps for entire Maldives in 1: 25 000 scale

Table 6: Name of the selected islands in 1: 1 000 scale

Table 7: Layer list for the preparation of 1: 25 000 & 1: 1 000 scale mapping

Table 8: List of hardware and software established at Male, Maldives

Table 1 Flight Plan Details for 1:40 000 scale photography

Block Number

Number of Main Run lines and direction

No. of tie lines

Approx. number of frames per run

No of frames as per tie line

No. of frames actually exposed

No. of Photos

selected for scanning

1 40 E-W 31 11-41 5-24 1635 989

2 9 N-S 8 41-68 8-11 626 311

3 11 N-S 22 84 5-12 1121 313

4 15 E-W 8 21-32 7-16 473 365

5 15 E-W 8 29 8-13 516 357

6 1 0 4 4 4

7 5 E-W 2 13 8 81 38

Total 4456 2377

Table 2 GPS Reference Station for Airborne GPS

Sl. No. Reference Station Block1 Hanimaadhoo 12 Alifushi 13 Rasdhoo 24 Nilandhoo 25 Kaashidhoo 36 Male 37 Kolhufushi 38 Veymandoo 49 Kadhdhoo 410 Kaadehdhoo 511 Gemanafushi 512 Fuvamullah 613 Gan (South) 7

Table 3 GPS Reference & Target / Rover Stations

Block-1Sl .No. Reference Station Target/ Rover Station

1 Hanimaadhoo Innafinolhu2 Alifushi Kelaa3 Kanditheemu4 Makunudhoo5 Feevah6 Maafaru7 Kothafaaru8 Dharvandhoo9 Thulhaadhoo10 Goidhoo11 Kanifushi12 Maabinhuraa

Block-2S.No. Reference Station Target/ Rover Station

1 Rasdhoo Thoddoo2 Nilandhoo Feridhoo3 Dhigurah4 Hukurudhoo5 Filitheyo6 Hulhudheli7 Kandinma8 Kudahuvadhoo

Block-3S.No. Reference Station Target/ Rover Station

1 Kaashidhoo Gaafaru2 Male Reethirah3 Kolhufushi Dhiffushi4 Guraidhoo5 Kunaavashi6 Fotheyobodufushi7 Raimandhoo8 Thuvaru

Block-4S.No. Reference Station Target/ Rover Station

1 Veymandoo Buruni2 Kadhdhoo Vilufushi3 Kandoodhoo4 Ishdoo5 Maavah6 Hithadhoo

Block-5S.No. Reference Station Target/ Rover Station

1 Kaadehdhoo Kolamaafushi2 Gemanafushi Vilingili3 Fares4 Gan

Block-6S.No. Reference Station Target/ Rover Station

1 Fuvamullah Fuvamullah

Block-7S.No. Reference Station Target/ Rover Station

1 Gan (South) Hithadhoo2 Hulhumeedhoo3 Gan

Table 4 Results of Aerotriangulation of entire Maldives shown as blockwiseBlock No.

Scale of Photography

No. of images

No. of GCPs

Pixel size(µm)

σ0

(µm)Empirical accuracy (RMS) of GCPsµX (cm) µY (cm) µZ (cm)

1 1: 40,000 824 13 21 10 29.2 15.4 18.3

2 1: 40,000 262 6 21 10 21.8 12.0 14.4

3 1: 40,000 458 9 21 10 25.2 8.5 3.5

4 1: 40,000 238 7 21 10 12.8 11.4 25.9

5 1: 40,000 260 4 21 10 5.6 1.6 4.3

7 1: 40,000 32 3 21 10 2.6 2.0 1.0

Table 5 List of maps for entire Maldives in 1: 25 000 scale

Block Sl. Number Map Sheet Number Total

1 1-2 43N 01 P SE, SW1 3-6 43N 02 K NE, SW,SW,SE, 1 7-9 43N 02 M NE, NW,SE1 10-12 43N 02 N NE, SW, SE1 13-15 43N 02 O NE, NW, SE1 16 43N 02 P NE1 17-19 43N 03 M NE, SW,SE1 20-23 43N 03 N NE, NW, SW, SE1 24-27 43N 03 O NE, NW, SW, SE1 28-31 43N 03 P NE, NW, SW, SE1 32-35 43N 04 M NE, NW, SW, SE1 36 43N 09 D SW1 37-40 43N 10 A NE, NW, SW, SE1 41-42 43N 10 B NE, NW1 44-47 43N 10 C NE, NW, SW, SE1 48-51 43N 10 D NE, NW, SW, SE1 52 43N 10 G SW1 53-54 43N 10 H NW, SW1 55-58 43N 11 A NE, NW, SW, SE1 59-61 43N 11 B NE, NW, SW1 62-64 43N 11 C NW, SW. SE1 65-67 43N 11 D NE, NW, SW1 68-71 43N 11 E NE, NW, SW, SE1 72-74 43N 11 F NE,NW,SE1 75-78 43N 11 G NE, NW, SW, SE1 79 43N 11 J SW1 80 43N 11 K NE, NW, SW, SE1 84 43N 11 L NW1 85-86 43N 12 A NW,SW 862 1 43N 04 K SE2 2-3 43N 04 L NE,SE2 4-6 43N 04 O NE,SW,SE2 7-10 43N 04 P NE, NW, SW, SE2 11-12 43N 05 I NE,SE2 13-14 43N 05 J NE,SE2 15 43N 05 K NE2 16-19 43N 05 M NE,NW,SW,SE2 20-23 43N 05 N NE, NW, SW, SE2 24-27 43N 05 O NE, NW, SW, SE2 28-31 43N 05 P NE,NW, SE2 32-35 43N 06 M NE, NW, SW, SE2 36-37 43N 06 N NE,NW2 38 43N 12 C SW2 39 43N 13 C SW2 40-41 43N 13 D NW,SW2 42-43 43N 14 A NW,SW

2 44 43N 14 B NW 443 1-2 43N 12 E NE,SE3 3-5 43N 12 F NE,SW,SE3 6-9 43N 12 G NE, NW,SW,SE3 10-13 43N 12 H NE, NW,SW,SE3 14 43N 12 I SW3 15-17 43N 12 J NW, SW, SE3 18 43N 12 K NE, NW,SW,SE3 22-23 43N 12 L NW, SW3 24-27 43N 13 E NE, NW,SW,SE3 28-31 43N 13 F NE, NW,SW,SE3 32-33 43N 13 G NE, NW, SE3 35-38 43N 13 H NE, NW, SW, SE3 39 43N 13 I NW3 40 43N 13 J NW, SW, SE3 43-46 43N 13 K NE, NW,SW,SE3 47-49 43N 13 L NW, SW, SE3 50 43N 13 O NW3 51-54 43N 14 E NE, NW,SW,SE3 55 43N 14 F NE3 56-58 43N 14 I NE, NW, SW 584 1 43N 06 N SE4 2-3 43N 06 O NE,SE4 4 43N 06 P NE4 5-6 43N 14 B SW,SE4 7-10 43N 14 C NE, NW,SW,SE4 11-12 43N 14 D NE,NW4 13 43N 14 F SW4 14-15 43N 14 G NW, SW4 16-17 43N 14 H SW,SE4 18-19 43N 14 L NW,SW4 20 43N 15 A NE,SE4 22-24 43N 15 E NE, NW,SW,SE4 26-27 43N 15 I NW, SW 275 1 43N 08 N SE5 2 43N 08 O NE5 3-4 43N 16 A NE, SE5 5-8 43N 16 B NE, NW,SW,SE5 9-12 43N 16 C NE, NW,SW,SE5 13-14 43N 16 D NE, NW5 15-18 43N 16 E NE, NW,SW,SE5 19-22 43N 16 F NE, NW,SW,SE5 23-26 43N 16 G NE, NW,SW,SE5 27 43N 16 H NW5 28 43N 16 J SW5 29-30 43N 16 K NW, SW 306 1 43M 09 F NE 17 1-4 43M 09 C NE,NW,SW, SE 4

Grand Total 250

Table 6 Name of the selected islands in 1: 1 000 scale

S. No. Island Name1 NILANDHOO2 FUNADHOO3 MAAMIGILLI4 NAIFARU5 VILLIGILLI6 GURAIDHOO7 HUVARAFUSHI8 GADHDHOO9 MALE

10 K_FUNADHOO11 HULHULE12 KEDHIKULHUDHOO13 MULI14 HITHADHOO15 HANIMAADHOO16 FOAMMULAH17 GAN (SOUTH)

Table 7 Layer list for the preparation of 1: 25 000 & 1: 1 000 scale mapping

Sl. Layer list Feature Remarks1 BOUNDARY_ISLAND POLYGON2 BUILDING_DUCT POLYGON3 BUILDING_GROUP POLYGON4 BUILDING_INDUSTRIAL POLYGON5 BUILDING_SHED POLYGON6 BUILDING_SINGLE POLYGON7 BUILDING_UNDERCONSTRUCTION POLYGON8 CANOPY POLYGON TREE_COVER9 CULTIVATION POLYGON

10 FOUNTAIN_AREA POLYGON11 LAGOON POLYGON12 MARSHY_LAND POLYGON13 PALMYRA_GROUP POLYGON14 PARK POLYGON15 PLANTATION POLYGON16 PLATFORM POLYGON ELEVATED_SURFACE17 PLAYGROUND POLYGON18 POND POLYGON19 ROAD_ISLAND POLYGON20 STADIUM POLYGON21 SWIMMING_POOL POLYGON

22 TANK POLYGON WATER_TANK(MANMADE)23 TANK_CIRCULAR POLYGON

24 TANK_DRY POLYGON25 TANK_OIL POLYGON26 TANK_SQUARE POLYGON27 WATER_TANK_SINTEX POLYGON28 WELL_AREA POLYGON29 BOAT_CHANNEL LINE30 BUILDING_ELEVATION LINE CHANGE ELEVATED LINES31 BUILDING_RIDGE LINE32 DEEP_WATER_LINE LINE33 DRAIN LINE34 EMBANKMENT LINE35 FENCE LINE36 FOOTBRIDGE LINE37 HEDGE LINE38 HELEPAD LINE39 JETTY LINE40 PARKING_AREA LINE41 PIPELINE LINE42 PROTECTED_WALL LINE43 ROAD_BLACKTOP LINE44 ROAD_BLACKTOP_CENTER LINE45 ROAD_BRIDGE LINE46 ROAD_CARTTRACK LINE47 ROAD_CARTTRACK_CENTER LINE

48 ROAD_CULVERT LINE49 ROAD_DIVIDER LINE50 ROAD_FOOTPATH LINE51 ROAD_METAL LINE52 ROAD_METAL_CENTER LINE53 ROAD_UNMETAL LINE54 ROAD_UNMETAL_CENTER LINE55 ROCKAWASH LINE56 RUNWAY LINE57 RUNWAY_CENTER LINE58 SAND LINE59 STEPS LINE60 STREAM LINE61 UNSPECIFIED LINE62 WALL LINE63 BUILDING_HEIGHT POINT64 FLAGPOLE POINT65 FOUNTAIN POINT66 IDGAH POINT67 MANHOLE POINT68 MOSQUE POINT69 NAVIGATIONAL_LIGHT POINT70 OHT POINT71 PALMYRA POINT72 POWERPOLE POINT73 STATUE POINT

74 TOWER POINT75 TREE_COCONUT POINT76 TREE_OTHER POINT77 WELL POINT78 TXT_COCONUT TEXT79 TXT_CULTIVATION TEXT80 TXT_SAND TEXT81 TXT_FEATURES TEXT82 TXT_NAME TEXT

* BOUNDARY_ISLAND_AREA POLYGON* BUILDING_GROUP_ELEVATION POLYGON

Table 8 List of hardware and software established at Male, Maldives

SL. NO DESCRIPTION1 ERDAS IMAGINE PROCESSING 2 ARC INFO BASE 9.0 3 AUTO DESK MAP 2004 4 LEICA PHOTOGRAMMETRY SOFTWARE(LPS) 5 LTO 2 Tape Data Cartridge6 24 PORT 10/100/1000T GIGABIT AUTO SENSE ETHEMET SNMP MANAGEABLE

SWITCH7 STEREO VIEWING EQUIPMENT WTRELESS LIQUID CRYSTAL GLASSES, IR

EMITTER FOR EACH WORK STATION8 SERVER SYSTEM FOR REMOTE SENSING AND DIGITAL MAP DATABASE

STORAGE AND DATA SERVING9 WORKSTATION FOR REMOTE SENSING, GIS AND DIGITAL

PHOTOGRAMMETRY OPERATIONS10 LARGE FORMAT INKJET COLOUR NETWORK PLOTTER11 HANDHELD GPS RECEIVERS

List of figures

Fig. 1 Methodology for mapping at 1:25 000 scale using 1:40 000 scale aerial Photographs

Fig. 2 Methodology for mapping 16 select islands in 1:1 000 scale using 1:6 000 scale aerial photographs

Fig. 3 Seven Geographical Blocks for planning, managing and execution of the project

Fig. 4 NRSA’s SKA B-200 aircraft

Fig. 5 GPS Survey Pre Target

Fig. 6 Simultaneous observation of GPS reference / Pre-target Control point

Fig. 7 GPS Control Survey Deployment Plan

Fig. 8 Pre-target Control point imaged on aerial photograph

Fig. 9 Numbering schema for 1: 250 000 scale

Fig. 10 Numbering schema for 1: 50 000 scale

Fig. 11 Numbering schema for 1: 25 000 scale schema

Fig. 12 Aerial photography & Mapping of Maldives - timeline

Fig. 1 Methodology for mapping at 1: 25 000 scale using 1: 40 000 scale aerial Photographs

FLIGHT PLANNING

GPS SURVEY REFERENCE

STATIONS FOR AIRBORNE GPS

PHOTOPROCESSING

SCANNING OF DIAPOSITIVES

AEROTRIANGULATION

& BLOCK ADJUSTMENT

GPS DATA PROCESSING AIRBORNE

GPS

DEM

ORTHOPHOTO

GIS GEODATABASE

RECONNAISANCE FOR PLANNING AERIAL SURVEY USING IRS-1D LISS-III DATA

AERIAL PHOTOGRAPHY

2D MAPPING

HARD COPY MAPS

FIELD DATA

Fig. 2 Methodology for mapping 16 select islands in 1:1 000 scale using 1:6 000 scale aerial photographs

HARD COPY MAPS

FLIGHT PLANNING

GPS SURVEY REFERENCE STATIONS FOR AIRBORNE GPSGCPs - POST POINTED

PHOTOPROCESSING

SCANNING OF DIAPOSITIVES

AEROTRIANGULATION& BLOCK ADJUSTMENT

GPS DATA PROCESSINGAIRBORNE GPS GCPs

GIS GEODATABASE

RECONNAISANCE FOR PLANNING AERIAL SURVEY USING IRS-1D LISS-IV DATA

AERIAL PHOTOGRAPHY

3D MAPPING & CONTOURS

FIELD DATA

Fig. 3 : Seven Geographical Blocks for planning, managing and execution of the project

Fig. 4. NRSA’s SKA B-200 aircraft

Fig. 5 GPS Survey Pre Target

Fig. 6 Simultaneous observation of GPS reference / Pre-target Control point

Fig. 7 GPS Control Survey Deployment Plan

Fig. 8 Pre-target Control point imaged on aerial photograph

Fig. 9 Numbering schema for 1: 250 000 scale

8NSheet Numbering for 1:250 000 scale

7N43N01 43N09 43N17 43N25 43N33 43N41

6N43N02 43N10 43N18 43N26 43N34 43N42

5N43N03 43N11 43N19 43N27 43N35 43N43

4N43N04 43N12 43N20 43N28 43N36 43N44

3N43N05 43N13 43N21 43N29 43N37 43N45

2N43N06 43N14 43N22 43N30 43N38 43N46

1N43N07 43N15 43N23 43N31 43N39 43N47

043N08 43N16 43N24 43N32 43N40 43N48

1S43M01 43M09 43M17 43M25 43M33 43M41

2S43M02 43M10 43M18 43M26 43M34 43M42

3S43M03 43M11 43M19 43M27 43M35 43M43

4S43M04 43M12 43M20 43M28 43M36 43M44

5S43M05 43M13 43M21 43M29 43M37 43M45

6S43M06 43M14 43M22 43M30 43M38 43M46

7S43M07 43M15 43M23 43M31 43M39 43M47

8S43M08 43M16 43M24 43M32 43M40 43M48

72 73 74 75 76 77 78

Fig. 10 Numbering schema for 1: 50 000 scale

Sheet numbering for 1:50 000 scale

0 15' 30' 45' 1deg1deg

43N01A 43N01E 43N01I 43N01M

45’'

43N01B 43N01F 43N01J 43N01N

30’'

43N01C 43N01G 43N01K 43N01O

15’'

43N01D 43N01H 43N01L 43N01P

0Sheets North of Equator

0 15' 30' 45' 1deg0

43M01A 43M01E 43M01I 43M01M

15'

43M01B 43M01F 43M01J 43M01N

30'

43M01C 43M01G 43M01K 43M01O

45'

43M01D 43M01H 43M01L 43M01P

1deg Sheets South of Equator

Fig. 11 Numbering schema for 1: 25 000 scale schema

Sheet numbering for 1:25 000 scale

0' 7'30" 15’0”15'0”'

43N01A NW 43N01A NE

7'30"

43N01A SW 43N01A SE

0' Sheets North of Equator

0' 7'30" 15’0”0’'

43M01A NW 43M01A NE

7'30"

43M01A SW 43M01A SE

15'0” Sheets South of Equator

Fig. 12 Aerial photography & Mapping of Maldives - timeline