Pressing problems in the current surveying practice in Trinidad & Tobago
Due to station destruction, points based on the Naparima 1955 datum are difficult to find and may be well away from the area of interest. Accordingly surveyors have adopted a pragmatic approach and often use old Cassini stations. This is achieved by applying a '‘transformation' to the Cassini point to obtain co-ordinates in Naparima 1955 – and vice versa. Unfortunately the transformation is always calculated on a local basis. This is undesirable as the values obtained are entirely dependent on the points used. Hence different surveyors using different points will obtain different answers. This leads to disputes regarding the correctness of the surveys.
Most cadastral surveys are not related to any datum. Although this approach deals with the short term need to register surveys it has the significant drawback that surveys cannot be related reliably to each other. Again this leads to disputes and significant additional survey effort to resolve such disputes. Philip, 1973 makes clear the defects of this approach.
Some surveyors are using the GPS (Global Positioning System). Lands & Surveys have three receivers, some are being used by private surveyors (exact numbers have not been determined) and UWI (University of the West Indies – St Augustine Campus) has two. In the absence of a National GPS Network, the use of GPS is problematical. Current practice is to use the existing geodetic control (Naparima 1955) and, in effect, compute a local transformation. This involves ‘distorting’ the GPS observations to fit the existing control. As the GPS is intrinsically more precise than the existing control this has the effect of degrading the final answer. A more serious problem is that the answer depends (again) entirely on the particular selection of points used. Hence different surveys obtain different results - giving another source of dispute. While talking to the surveyors it was apparent that some do not trust GPS to give good results.
The
most obvious weaknesses in our current practice
The current practice of using both Naparima 55 and Cassini datums, and using piecemeal transformations between the two is leading to dispute and confusion in the surveys. Even two errorless surveys, based on different realisations of the same datum, will lead to conflicting results. Surveys based on differing datums, or a poorly defined datum, are often impossible to relate to one another.
The GPS equipment available in Trinidad and Tobago (mainly Trimble 4000 series receivers) is known to give excellent results. Hence the poor results sometimes obtained may be attributed to the lack of a well defined geodetic datum. This in turn is leading to resistance to the use of GPS (however, the cost of equipment is probably a bigger factor).
Two private surveyors interviewed, Mr Winston Mohammed and Mr Sasha Ian Addo, have developed an efficient method of working with GPS. They have achieved this by adopting ‘known’ co-ordinates for some stations and using the same transformation throughout Trinidad and Tobago. This is exactly the thrust of the recommendations made in this paper, but with appropriate attention paid to national standards. However the surveyors are using different parameters and, what’s more, they differ from those given in Geodetic Services, October 1999. The various parameters are shown in the table below.
Should Trinidad & Tobago continue to use Naparima 1955?
The primary purpose of the geodetic datum is to provide a referencing system to which positions of features may be related. In the past the area over which a datum could be used was limited and so many such datums exist. Because co-ordinates for the same point have different co-ordinates in each datum it is essential that the datum used is known and well defined. Unfortunately this is not the case in Trinidad and Tobago. The situation is further complicated by the fact that no reliable connection exists in either datum between the two islands of Trinidad and Tobago. This omission is due to the difficulties in establishing such a connection using ‘conventional’ surveying equipment. It seems beyond doubt that the most used datum is Naparima 1955 consequently there exists a significant amount of work in this datum. It is recommended that this datum continues to be used for land survey in Trinidad and Tobago.
Surveys are carried out for many purposes. Maps and plans are prepared in many disciplines such as land management, cadastre, resource exploitation, nature conservation etc. If these diverse data sources are to be compatible then they must all use a common co-ordinate system. For example, a conservationist may map an area of special interest which the Authorities seek to have protected; later an engineer designs a road which passes through the same area. Unless both specialists base their measurements on the same co-ordinate system the road engineer will be unable to relate the position of the road to the position of the nature conservation area.
Another example could involve two nations who seek to define their boundary in an unambiguous way. An internationally accepted datum will allow this work to proceed and the results to be widely accepted. A well defined, and accessible, geodetic datum will allow all surveys to relate to each other. This then allows information to be exchanged and used with maximum benefit to all concerned.
The need for a coherent co-ordinate system is not new. Philip, 1973 gives an excellent account of why a national co-ordinate system is so important. Although written nearly thirty years ago the justification presented is still valid today and is well worth re-visiting.
Under subsection 2(1) of the Act, the interpretation of word “surveyor”
"includes a hydrographer, engineer surveyor, cadastral and land
management surveyor, photogrammetrist, geodesist or cartographer or as may be
prescribed by the Board"
The Act defines cadastral surveying and land management as a single category of “surveyor”, rather than as two separate categories. Since land management is not normally regarded as a category of land surveying the Consultant considers it advisable to delete the words “and land management” from the definition.
It is evident that the Land Survey Board, to which the subsection refers, has very broad powers to prescribe other categories of surveying if it chooses to do so. This by no means suggests that the Board would ever act irresponsibly or without consultation with other affected professions. But there remain certain activities, of which the creation, operation and maintenance of a Geographical Information System (GIS) is a prime example, that cannot be fairly said to belong exclusively to any single profession, for its claimants can include surveyors, engineers, geographers, computer scientists and others. Resistance from those professions could be expected if the Board were to prescribe the practitioner of GIS as a surveyor.
The Consultant prepared a set of Best Practice Guidelines for cadastral surveying. These guidelines, which deal with law, monuments and boundaries, supervision, and fees and advertising are intended to supplement the Act, Regulations, Code of Ethics and Rules.
In the Consultant’s opinion, the Land Surveyors Act, 1996, the subsidiary legislation made thereunder and the Best Practice Guidelines should provide cadastral surveyors with direction and advice that will assist them in the practice and promotion of their profession. In addition, these various rules should also help to ensure that cadastral surveys in Trinidad and Tobago are carried out to the required technical standards. It should be observed, however, that a regulatory framework by itself is not enough. There must also be adequate enforcement.
Is a cadastral survey required in order to register a parcel and obtain a certificate of title under the newly enacted (but not yet promulgated) Land Adjudication Act 2000?
The Registrar General expressed uncertainty to the Consultant as to what type of survey information will be needed for registering an adjudicated parcel under the new Act. The Consultant understands that each parcel adjudicated under the Land Adjudication Act will be demarcated on the ground and identified by a Unique Parcel Reference Number on a Parcel Identification Map which shows the correct topological relationship of all parcels on the map. This information is sufficient to register the parcel and issue a certificate of title. Any owner of a registered adjudicated parcel who requires a cadastral survey plan that shows the bearings and distances of the parcel boundaries and the parcel area could obtain it, but the survey and preparation of the plan should be at the owner’s expense.
A Certificate of Comfort is a personal, non-transferable right. It provides the holder with protection against ejectment, but it does not create an interest in land. The Act does not require the boundaries of land occupied by a squatter to be surveyed for the purpose of issuing a Certificate of Comfort. Yet the LSA needs to determine the geographical location of the site by a rapid, but reasonably accurately, method that does not involve undue expense. Among the methods considered are:
a) the use of kinematic GPS to determine the coordinates of the centroid or some other point within the site,
b) the identification of the site from recent air photography, and
c) the utilisation of census enumeration diagrams.
A Statutory Lease for a period of 30 years may be acquired by a squatter who has obtained a Certificate of Comfort, or by a tenant in occupation of land in a Designated Area or a Land Settlement Area. A Statutory Lease may not be assigned or transferred, except to the State, but it is transferable for the remainder of its term in the estate of a deceased person according to law. A survey of the boundaries of land held under an application for a Statutory Lease is required before the lease will be issued. Only a Trinidad and Tobago Land Surveyor should be permitted to make this survey. At the present time (May 2000), several Statutory Leases are in preparation but none has been issued.
Is engineering surveying practised by professional or technical surveyors?
The consultant encountered, at every meeting, an intense and passionate debate concerning the status of engineering surveyors. Such debate is a healthy sign of a vibrant profession and is something that should be harnessed in an atmosphere of inclusivity rather than feared. One of the healthiest aspects is that every surveyor, from a wide range of abilities and backgrounds, was keen to stress their own aspirations and hopes for the future. The phrase “it is good for my country” was attached to many such hopes that were expressed and, once again, this underlines a strong ethical strain running through the surveying profession. The consultant is sure that surveyors would like to earn more money, but the subject of earnings was not mentioned (unless the consultant raised it in the first place) by a single surveyor. Their number one concern was the way in which their chosen profession was heading; this is extremely refreshing.
Types
of Practicing Engineering Surveyors
The registered (licensed) surveyors who have either obtained a degree at UWI or have been “grandfathered” into the licensed / registered fold. “Grandfathered” is a term that has been used frequently during meetings and, in the interests of plain English the consultant will adopt it. These surveyors have, for the most part, been educated to a high academic and all-round level; they have knowledge of a wide spectrum of land surveying. Part of their repertoire is engineering surveying and, from what the consultant could glean during meetings, their engineering surveying is of a high order.
The ex-John Donaldson (JD) Institute surveyors who will (by virtue of the date at which JD ceased to offer such courses) be at least in their late 30’s and more likely to be in their mid-40s. These surveyors (it is estimated that there are now between 4 and 7 in private practice) appear to have, since their days at JD, attained more knowledge by attending overseas courses and by extensive site-experience. Some of them possess a good stock of modern instrumentation and are working for reputable foreign companies on development sites on both the islands of Trinidad and Tobago. These surveyors feel aggrieved that the 1996 Act excludes them from their everyday activities, which they have been doing competently for at least 15 years.
Thirdly, there are many engineering surveyors (perhaps up to 50) who should be considered as technicians. The term “technician” is not intended to be derogatory. Technicians are a vital part of every profession and many technicians go on to the very heights of those professions. However, the only way to harness (and control) the energy of those technicians is to have a technical grade of engineering surveyor within the regulations. Experience in the UK is that it is infinitely better to have a system whereby everyone feels they are part of what is “going on”, rather than leaving people outside the system. Technicians should be valued and included but should work under the supervision of professionals. This is accepted in other professions (and in the UK) and there is no reason why it should not be adopted in T&T.
The Code of Best Practice (CBP) prepared by the engineering surveying LUPAP consultant can be considered in two parts:
The first part is the description of methodology and practice. The purpose of this is largely to confirm methods that are already widely used. However, there was a general welcome for the idea of a CBP from engineering surveyors as a base reference document for day-to-day use. The CBP should not become a fossilised document that is confined to a shelf in each surveyor’s office. It is very much hoped that engineering surveyors will inform the Land Surveying Board of suggested changes to the CBP so that, at regular intervals, the Board can issue revisions to it. The CBP is intended to be a living document that evolves with the coming changes in technology.
The second part is a Standard List, “the list”. The list is intended to include every conceivable feature that may be encountered by an engineering surveyor on-site. More importantly, the list has been separated (as an Annex) from the main body of the CBP so that it can be used as an aid to everyday surveying. Engineering surveyors will be able to either copy the list in its present form, or prepare their own “short-lists” from it. The list has been designed so that it can be used by client organisations as a request-sheet, by surveyors themselves as a site-check list and as a client-confirmation list. The list should help to clarify the expectations of clients with regard to work they receive from a range of different surveyors.
Recognizing the
implications of Professional Indemnity Insurance (PII)
PII is included in the 1996 Land Surveyors Act (Section 30) and in the 1998 Land Surveyors Regulations (Section 12).
There is a general lack of knowledge of the insurance field and it is recommended that a respected insurance broker (or panel of brokers) be invited to give a presentation to all land surveyors (including engineering surveyors and technicians) on the subject of PII. This would allow the full implications of PII to be explained.
Why is it important to know which survey co-ordinate system is being used?
At present 3 such systems are commonly used in Trinidad and Tobago:
· Naparima 1955 – current mapping system
· Cassini 1903 – old mapping system
· WGS 84 – Global positioning system
The example below indicates the magnitude of errors that might occur through misunderstanding, or misapplication, of the co-ordinate system. To make the quantities understandable the example is set in Port of Spain, but applies equally throughout the whole country and its archipelagic waters.
118 Frederick Street (Lands and Surveys Division headquarters) appears on current detailed maps, and the Naparima 1955 co-ordinate values of its position may be accurately read, to within about a quarter of a metre. If those identical co-ordinate values are then plotted on an old map made on the Cassini 1903 co-ordinate system the position would appear in the Church of the Immaculate Conception at the junction of Park and Henry Streets, roughly 250 metres south east of 118 Frederick Street.
Similarly if those same identical co-ordinate values were located using a GPS set, which makes its measurements in World Geodetic System 1984, then the location would be in the south west corner of the Port of Spain General Hospital close to the junction of Charlotte and Belmont Circular Streets, roughly 350 metres north east of 118 Frederick Street. Uncertainties amounting to several hundred metres could be critical with regard to navigation hazards
All of the marine traffic using the coastal waters of Trinidad and Tobago now have GPS receivers and WGS 84 should be confirmed as the new co-ordinate system of choice for all new charting activity. The new regulations issued by the IHO stipulate significantly tighter accuracy requirements than have been used in the past for port approaches, particularly where hazardous cargoes are involved, and the requirement for these surveys is such that 100% bottom search is a necessity.
Hydrographic surveying has gone through fundamental changes in measurement technology within the last ten years. Multibeam acoustic and airborne laser systems now provide almost total seafloor coverage and measurement as compared to the earlier sampling by bathymetric profiles. The capability to position the data precisely in the horizontal plane has been increased enormously by the availability of satellite positioning systems, particularly when augmented by differential techniques. In the offshore industry, undersea positioning using hydro-acoustic methods allow great precision to be achieved.
Depth measurement technology has kept pace with increases in horizontal positioning accuracy, and whilst many hydrographic surveys will continue to be conducted with single beam echo sounders which only sample discrete profiles of the seafloor, it is likely that 100% bottom search techniques utilising a combination of multibeam echo sounders and side-scan sonar technology will be employed for critical areas.
Users of hydrographic data make up a much more diverse group than has previously been recognised. Hydrographic surveying and data acquisition is not just carried out for the compilation of nautical charts. Hydrographic data is also important for coastal zone management, environmental monitoring, resource development (including hydrocarbon and mineral exploitation), legal and jurisdictional issues, ocean and meteorological modelling, engineering and construction planning and many other uses. To increase its usefulness, users require data that is more up to date, detailed, reliable, and in digital form.
Are
there reliable charts of the offshore waters of Trinidad and Tobago?
The current charts issued by the Hydrographic Unit of the Lands and Surveys Division date from the late 1980’s. As detailed above the past ten years has seen a dramatic change in technology and acquisition methods concerning classical hydrographic surveying for this purpose. The methodologies of both acquisition and production as well as the levels of accuracy and completeness have all changed.
During this period the number and size of cargoes passing through Trinidad and Tobago territorial and coastal waters have increased dramatically. The nature of their cargoes has also changed, with a significant increase in the number of environmentally sensitive if not hazardous cargoes. There has also been a significant increase in the number of dredging operations as well as coastal developments concerned with development of the Chaguaramas area as well as others in Port of Spain and the Gulf of Paria generally. Off the west coast there have been significant infrastructure developments in support of the Oil and Gas production industry with a number of pipelines now in place. Development of gas fields to the North of Trinidad will soon result in a major gas line being laid through the Gulf of Paria down to Port Fortin.
Accurate modelling of the dispersion of oil spills and creation of ocean current and circulation models in and around Trinidad and Tobago is presently hampered by poor knowledge of the bathymetry.
Trinidad and Tobago is a member of the International Hydrographic Organisation (IHO), and hence have an obligation to ensure that hydrographic surveys and charting within their waters are performed to International standards and are made available to the various international charting agencies for inclusion on their chart series.
The Hydrographic Unit of Lands and Surveys Division is currently moribund. Through a sequence of Ministry moves, compounded by promotion and/or departure of senior officers and lack of maintenance of equipment and vessel, it no longer has an active charting capability. However the requirements and commitment to perform the necessary surveys still exists.
To re-equip and re-staff to the level
necessary to fulfil its commitments would be uneconomic.
The logistics and cost of
maintaining a full suite of hydrographic equipment is such nowadays that it can
only be afforded by the major government (USA, UK, France) hydrographic services
and by multi-national survey companies. Most
developing countries with significant coastlines are now only able to meet their
obligations and commitments by commercial contract.
The Hydrographic Unit can still have a significant role to play through project management and QC of data acquisition and chart production and in undertaking the move of existing data from Naparima 1955 into WGS 84 for the issue of a new chart series based on WGS 84.
Maintenance and sale of national maps.
A modern high accuracy Zeiss photogrammetric scanner was installed as part of the initial establishment of the digital map production facility (DMPF). Although this equipment is currently not utilised it will be essential to future revision operations. It is therefore recommended that this scanner be regularly maintained so that it does not fall into disrepair and used occasionally to maintain staff knowledge.
To facilitate the expansion of DMPF, stereoplotter operators are currently in transition from analogue to digital methodology. This has resulted in three stereoplotter operators being subsumed within DMPF, and analogue equipment being left unused within the old building in Richmond Street. It is highly unlikely that the old analogue plotting instruments (Wild A-8 and A-10) will be required in the future by Lands & Surveys Division and therefore it is recommended that this equipment either be sold or scrapped to release the accommodation for other purposes.
Stereoplotter operators are currently gaining experience in digital data processing by being involved in data validation of the new topographic dataset. This training and experience is essential if they are to go on to using digital photogrammetric workstations.
The Intergraph software is fully installed and being utilised to quality control the new topographic data which is currently being received. It is important to maintain and increase staff knowledge of the software capabilities.
The data has been extracted from air photography captured in 1994 and revision (or up-dating) will be necessary following receipt of the topographic data. Options for revision all involving air photography include, stereographic data capture, mono-plotting, and/or graphic survey techniques. The latter two techniques would require some staff training to be fully efficient.
Large levels of development are taking place throughout Trinidad, especially around Port of Spain, the East-West corridor and inland from San Fernando. There is also considerable development both planned and under construction in Tobago (Hilton Hotel complex etc).
Planning for the revision process should start immediately to ensure that the topographic mapping remains useful and that further time lags do not occur. The Lands & Surveys Division will then be well placed to implement revision on receipt of the new topographic data.
At present it seems unlikely that any ground completion will be carried out, this reinforces the need to capture new photography and implement a Revision Policy for maintenance of the new mapping. It is recommended that Lands and Surveys Division develops proposals to implement revision processes; and it is also recommended that planning is started immediately for the supply of new photography in priority areas of known change.
Investing in expensive digital Photogrammetric equipment
It is recommended that the purchase of a Digital Photogrammetric Workstation (DPW) is commenced immediately assuming Lands & Surveys wish to carry out map revision using photogrammetry. Due to the terrain and significant levels of development throughout the Islands since the 1994 photography was captured photogrammetric surveying is the only realistic method of capturing this new detail.
These conclusions are drawn because:
Ø although some surveys could be done using ground methods, especially in areas where there is good control and the terrain is relatively flat, it is unlikely that sufficient survey staff could be made available for this work;
Ø land surveyors do not currently possess the Graphic Survey skills which speed up topographic survey revision and would need to be trained in this skill;
Ø significant housing and other development has taken place in areas with large height differences and dense vegetation;
Ø the Division already has available stereo-plotter who are keen to carry out the work.
The archive of contact prints and film is of high national value and should not be allowed to become fragmented and damaged. This archive will be of immense value in future years in being able to act as a reference to the state of the Nation’s land at the time of exposure. Geographic Information Systems (GIS) and land analysis are becoming increasingly important and the Lands & Surveys Division has a duty to maintain this archive. It is therefore recommended that the prints and film be co-located, indexed and stored in good conditions.
It is apparent from meetings with surveyors in both Trinidad and Tobago that there is a need to standardise the way engineering surveyors carry out the technical aspect of their work and present it to their clients. The Standard List and the Code of Best Practice have been designed as base-documents which can be built upon and revised and re-issued from time to time.
Liaison with other Professions
There is a need for the professions connected with land, design and construction to liase with each other much more than they do at present. It is recommended that meetings are held, as part of CPD (see below), to ensure that the professions are aware of each others capabilities and problems. It was, for example, very interesting during the meeting in Tobago to hear the views, that were expressed by civil engineers, about the surveying profession. Sometimes it is instructive and enlightening for professionals to hear, at first-hand, how other professionals perceive them.
Continuous Professional Development
Continuous Professional Development (CPD) is recognised as being a vital part of every modern profession and is specifically referred to in the Land Surveyors Regulations 1998, Para 15. The description of CPD in the Regulations is comprehensive and adequate. However, surveyors should be pro-active in liasing with other professions, with surveying instrument representatives, and other professionals in arranging lectures which comprise “activity” for the purposes of CPD. The consultant has considerable experience of lecturing for CPD purposes in the UK and has found that most professions become (a year or two after the inception of CPD) short of subjects for meetings and lectures. Inter-profession CPD provides a greater variety of subjects and more valuable contact between professionals.
Engineering surveying is not a highly regarded profession in T&T. This is probably because engineering surveyors are perceived as people who hammer pegs into the ground on muddy construction sites. Whilst there is an element of truth in this, it is also the case that many engineering surveyors control the positioning of high-tech installations (machinery, for example, is often positioned to accuracies of 1mm) and also solve problems where design-faults need to be addressed during the construction process. Ordinary CPD meetings may help to raise the profile of engineering surveyors. Another suggestion is for engineering surveyors to invite other surveyors and members of other professions to visit high-prestige sites as a CPD session. For example, a “guided tour”, by an engineering surveyor, of a large project such as the new airport terminal may illuminate the way in which engineering surveyors have a high input into such projects.
Implementing Value-Added Services to Engineering Surveying
There is a need to be aware of the value-added items which engineering surveyors can offer to their clients. The national digital data coverage will soon be available and engineering surveyors should experiment with “slotting” their detailed (perhaps 1:200 and 1:500) surveys into the digital data. The prospect of providing clients with a detailed survey with a collar of digital data around it may be very attractive to those clients.
Engineering surveyors should be constantly searching for ways in which the client can be provided with as many peripheral items as possible, as well as the engineering survey itself. Thus, over the months and years, clients will become used to relying upon the engineering surveyor for all kinds of map-related and site-related services over and above the traditional product. At every meeting with surveyors it was found that, although the concept was new, it was generally agreed that such flexibility will be necessary to survive in the new millennium.