ROLE OF HYDROGRAPHY IN COASTAL GIS
A. Muralidhar,
National Hydrographic Office, Dehradun (IN)
Introduction
The convergence of technologies used in collecting and sharing hydrographic
data has resulted in significant increases in the responsibility of a Hydrographer
in collating the data into a GIS. Additional data can be collected in addition
to the core bathymetry data which can be used more widely in fields such a
marine resource management, environmental protection, flora and fauna along
the coastal belt. Collection of various data in digital media in a suitable
a format for subsequent integration into an open GIS for archival at any time
later. This paper focuses on a Hydrographers role in achieving this objective.
Data definition
The type of Hydrographic data to be collected along the coast is governed
by the end objective of the survey. Therefore, from a Hydrographer's perspective,
the end objective data collection can be broadly classified as generic data
and mission specific data type.
Some of the Hydrographic data of generic nature
are as follows:
(i) Coastline - High Tide Line - Low Tide Line
(ii) Type of foreshore - Sandy, muddy
(iii) Type of Hinterland - Barren, Rock Town ship Village, Industry
(iv) Vegetation in the coast- Cultured land Jungle
(v) Fishing/Traffic density near the coast - Dense fishing load vessel traffic
(vi) Type of Coast. - Cliffy, Rcky, Coral
(vii) General depth along the coast - Shallow, steep gradient
The mission specific data contains information that is relevant to that specific mission. Two samples of mission specific data are as follows :
| (a) Mission |  |
Amphibious Operation Survey : |
- Type of seabed along the approaches.
- Tidal Range
- High Density Bathymetric Data.
- Type of Sand.
- Accessibility to highway, village railway station
- General weather in the area
- Approach transit marks
- Gradient of the beach
- Seabed texture of the approach area
- Currents in the area
- Colour of water
(b) Coastal Zone Management Survey :
- Type and dimension of the beam, beach front.
- Type of Sand.
- Tourism near shore
- Fishy/Shipping Traffic Density
- Marking, distance and area of HTL, LTL from fixed shore points
- Availability of pollutants
- Flaura and Fauna along the coast
- Habitation along the coast
Coastal Objects of Interest
The Hydrographers have the rare privilege of visiting uncharted area both
in land oceans, hence it is pertinent to collect all possible data in addition
to data required hydrographic requirement alone.
A standard library of coastal objects of interest needs to be built for case
of access on a GIS platform. A suitable template can be made and the formation
can be filled in the field with a database software loaded on the palmtop/note
pad. Some of the coastal objects of interest are as follows:
(a) Type of sand.
(b) Tidal range
(c) Type of current, wave data
(d) Colour of water.
(e) High tide and low tide line
(f) Type of Sea bed
(g) Vegetation
(h) Habitat
(i) General weather in the area
(j) Lay of the beach
(k) Fishing activity
(l) Traffic Density - shipping
(m) Population
(n) Culture and livelihood of coastal population.
(p) Gradient of coast.
Classification of Objects
Classification of Objects into line/point/polygon with attributes is based
on the type of objects. For example, the High Tide Line/Low Tide Line would
fall under line the area between high water/low water line would fall under
polygon and the depths/light house will fall under point feature. These are
classified keeping in mind the cartographers requirement/depiction in nautical
charts.
Data Capture
Data capture till the recent past has been totally manual method of physical
observation by the surveyors and a record in the notebooks based on the individuals
knowledge on Hydrography and Cartography. Some of the disadvantages of the
manual methods are:
(a) Dilution of exact facts in the process of transforming
data
(b) Estimation of parameters and distance for which instruments were unavailable
(c) Loss of data during retrieval of manual data.
Digital Data
The influx of digital devices paved way for data collection in digital form
that overcame most of the drawbacks of the manual mode of data collection.
With the advent of these technological devices the data became more accurate,
retention of ground facts till the depiction on chart. Some of the devices
include GPS, Automatic Tide Gauge, Anemometer, Palm Top, Net Pad, Digital
Camera, Multibeam/Single Echo sounder, Remote Sensing, Satellite Imagery,
softwares for data enhancement, calculation, etc.
The semi-digital mode of data captures involving equal distribution of data
collection between digital and manual. The digital mode of data collected
is assimilated on a common platform and analysed manually as per the end objective
and incorporate in the flow of nautical chart production on a specific task
requirement.
The fully digital mode of data capture involve no manual intervention in the
mode of data collection in the field or assimilation and analysis off the
field. These are possible by integration of all the digital device data on
a common format for interoperability in the analysis stage in the software.
Though the only manual interference is guiding the data as per the needs of
the end objective at various stages of data analysis. But the field data collection
is all on digital media. The subsequent paragraphs would enumerate the methodology
of the coastal data capture into the GIS stage. The international standard
S-57 has the potential to be used in the base map for most GIS operations
on data collected in coastal zone. This would be common link for development
of a nation wide GIS enabled data base for the oceanic and coastal domain.
Methodology
The prime objective is to collect all possible/relevant data in digital form.
The format has already been standardized for interoperability like in the
nautical charting S-57 format.
| Sl. | TOOL | Data |
| 01. | GPS associated software | Coastlining - HTL - LTL |
| 02. | Tide | ATG |
| 03. | Digital Camera Lay of Beach | Type of foreshore |
| 04. | Multibeam Echosounder | Depth sea bed classification |
| 05. | Remote Sensing, Satellite Imagery | Sediment flow, lay of beach, spectral information, water colour |
| 06. | Anemometer | Wind direction |
| 07. | Net pad/Laptop | Attributes/information data that cannot be capture by digital mode |
| 08. | Digital level and theodolite | Vertical heights and merging of with horizontal datums |
| 09. | Moored current meter data | Underwater and surface currents |
Data Management
Since the data is being collected from various type of equipment with its
own data format there is a need for accepting all these data into a common
platform on software. This GIS software would be further used for analysis,
finding trends and pattern.
Survey equipment format should have flexibility of inter operability
on the GIS software. The basis of data collection should be strictly governed
by the following.
(a) End objective of the data is kept in mind at all stages.
(b) All the possible parameters needs to be recorded in the field ina standard
defined format something akin to the S-57 format in international charting.
(c) Integration with other data at suitable stage. The data collected by each
device should be assigned a layer for demanding the information and comparison
when required by the software or feasibility of upgradation when required.
(d) The data collection in the field needs to be checked for quality by a
database verification software on its completion of attributes and generate
a report on lack of attributes in certain fields if found amiss.
(e) The data collected in the filed is to be annotated by typical description
in the attribute so that the facts are intelligent. The type of attributes
to be filled is the sole responsibility of the man in the filed, this where
the professionalism of the Hydrographer comes into play.
Product
The proof of the quality and type of data collected in the field is evident
from the lay end digital map when being put up to use. The shortcomings of
the improper data collection are glaring on a chart/toposheet . The factors
that have direct relevant to the chart and the type, quality and quantity
of data to be collected in the field are :
(a) Scale.
(b) Projection
(c) Symbols
(d) Datum commonality (vertical and horizontal)
(e) Format
(f) Eventual integration with GIS.
Analysis
From the GIS package of intelligent information the trends and pattern can
be predicted based on the customized algorithm by a mathematical or visual
mode. In case of classified information on the analysis needs to be classified
then the same needs to be secured and only the information of generic nature
to be in open domain.
Today's telecommunication technology has augmented the means of sharing of
data by website, digital media network. The releasing of data in these media
needs to be filtered based on the possible accessibility by the general public
user domains requirement on the need to know basis.
Applications
The information available on a open domain should be of public utility like
disaster management development plan, tourism, flaura fanna, Industry, Fishery,
navigation, reducing the harsh sea condition on coastal belt, accurate and
secure precise information for amphibious warfare.
Law
Incorporation of law factors into the coastal GIS based on the classification
of zone in the charts into CRZ I, II, III area and creating hyperlinks of
the legal aspect of these zone to an associated website. Violation of any
laws as per the CRZ regulations based on the updated data on ground should
send a message to the law governing authority by a URL link. The CRZ demarcating
agency should be an isolated kind based agency like defence sector. The law
making bodies should use these GIS tools to assist in decision making on aspects
like coastal habitat, ecology, population, environment, archaeologist development,
tourism, port authority, etc., by proper visualization like 3D images, mathematical
analysis, trends and pattern which are based on logical and mathematical methods.
Know how of the rights of use, ownership and stewardship in coastal areas,
that is who has the right to make and enforce decisions on the matter enumerated
below:
(a) Limits of private and public ownership on upland property
(ordinary, high water mark)
(b) Limits of private rights below high water (e.g. water log, aquaculture
site leases, oil and gas licenses, fishing licenses)
(c) Municipal, County, Provincial and Territorial limits of jurisdiction and
administration
(d) Government Departmental limits
(e) Pipelines and cable rights of way
(f) Environmental protection areas (wet land, marine protected areas, coastal
zone management)
(h) Military limits (e.g. disposal and weapon firing ranges)
Summary
The coastal GIS data of a very generic nature once evolved should be available
on public domain. However, the specific, detailed information should be available
only on demand/payment basis and certain information of national security
nature should be completely isolated from public domain data. The amalgamation
of coastal GIS data will assist the mankind in multiple fields of development
and prevention or reduction of disaster along the coastal belt.