report on consulting services for the creation of a...
TRANSCRIPT
Report on consulting services for
the creation of a coastal area related geodatabase including processed historical
maps from French archives as well as recent GIS material and the estimation of
coastline regression since 1904 in the southern Mekong Delta
by Roman Sorgenfrei
Geodata Management Advisor
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Contents 1. Introduction ................................................................................................................................................... 2
2. Collection of historical maps .......................................................................................................................... 3
2.1. Processing of historical maps from the French colonial archives and map series L7014 ...................... 4
2.2. Limitations ............................................................................................................................................. 5
3. Google Earth satellite images ........................................................................................................................ 5
3.1. Recent images ....................................................................................................................................... 5
3.2. Time series – historical satellite images ................................................................................................ 6
3.3. Note about users licence for Google Earth imagery .............................................................................. 6
4. Geodata collection of already available data from GIZ offices ...................................................................... 7
5. Shoreline change analyses ............................................................................................................................. 8
5.1. Shoreline change rates (DSAS) .............................................................................................................. 8
5.2. Notes ................................................................................................................................................... 10
5.3. DSAS – Results ..................................................................................................................................... 11
5.4. Shoreline area changes ....................................................................................................................... 16
6. Conclusion and recommendations ............................................................................................................... 20
Paths of stored data and structure ....................................................................................................................... 21
References ............................................................................................................................................................ 24
Appendices ............................................................................................................................................................ 26
Appendix I – Historical maps collection - 1904 .................................................................................................. 26
Appendix II – Historical maps collection - 1924 ................................................................................................. 27
Appendix III – Historical maps collection - 1953 ................................................................................................ 28
Appendix VI – Historical maps collection - map series L7014............................................................................ 29
Appendix V – Google Earth Satellite Images - recent images (2014 & 2015) ................................................... 30
Appendix VI – Google Earth Satellite images - recent images (folders) ............................................................ 31
Appendix VII – Google Earth Satellite Images - time series (folders) ................................................................ 31
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1. Introduction
Funded by the governments of Viet Nam, Germany and Australia the Integrated Coastal Management
Programme (ICMP) is a development programme implemented by the Deutsche Gesellschaft für
Internationale Zusammenarbeit (GIZ). To support the Vietnamese authorities in preparing the coastal
area of the Mekong Delta for a changing environment as well as to lie the foundations for sustainable
growth are its objectives.
One component of ICMP is the task team Coastal Protection. Its focus lies on the stabilisation and
security of the coastline of the southern Mekong Delta. This shall be achieved with the development
of an Integrated Coastal Protection Plan for the southern Mekong Delta. Important pillars of this
programme component are the restoration of the foreshore area, coastal engineering measures to
enhance natural processes and the planning of sea-dykes based on local circumstances. The mangrove
belt along the coast plays a significant role in securing the residents and livelihoods in coastal areas.
Therefore the rehabilitation of mangroves is an essential part of coastal protection. ICMP supports
provinces and institutions in the development and application of science-based instruments with the
aim of finding the best appropriate and effective measures for coastal protection investments.
To understand the morphological development of coastlines, the original hydrology of coastal areas
as well as the former distribution of mangrove forests, a key tool of ICM is used, the analysis of
historical maps, aerial images, and satellite images (ALBERS et al. 2013, p. 98f.). Already in the past the
former GIZ-project “Management of Natural Resources in the Coastal Zone of Soc Trang Province”,
now part of ICMP, commissioned the creation of a historical shoreline geodatabase. It includes
historical maps from French colonial archives, aerial photos, recent satellite images, as well as digitised
land-use shape files (HNEE 2013a & 2013b). The database helps to understand historical land-use and
shoreline changes along the coast of the province and hence the planning progress of future activities.
Recently, ICMP gathered further historical maps from the French colonial archives covering the
remaining area of interest in the Mekong Delta. Additionally, it is planned to also obtain further
historical aerial photos for these regions. These historical datasets can be compared with recent
satellite images, land-use and irrigation maps. Thus, the natural and anthropogenic forces which
shaped the coast of today and which challenge the plans for the future can be better understood for
the whole programme area.
The aim for this consultancy was to combine the up to now separately stored coastal area related
geodata of the GIZ provincial offices into one categorised archive and to expand it with further
material like recent satellite images from Google Earth. The result is a digital coastal area related GIS
database which can be used as a source of maps and map contents for a Coastal Atlas of the southern
Mekong Delta. The coastal area related GIS data is available in a format which makes them usable for
various future applications.
Furthermore the collected maps and images were used to digitise the changing shorelines from 1904
till 2015. These were then used for shoreline change analyses to calculate regression and transgression
rates as well as area changes. The rates were calculated using the ArcGIS 10 extension DSAS - Digital
Shoreline Analysis System (U.S. GEOLOGICAL SURVEY 2015a).
In addition, recent data for the whole Mekong Delta from the Southern Institute of Water Resource
Planning (SIWRP) and Sub-FIPI (Institute for Forest Inventory and Planning) should have been included
into the database. Unfortunately it was not possible to get these data until now.
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2. Collection of historical maps
Of interest for coastal area related analyses are maps with a scale of at least 1/100 000. Is the scale
smaller, map contents like shoreline and hydrology are too inaccurate and often too aggregated to be
used for analyses, e.g. analysis of shoreline changes over time.
The historical maps from the French colonial archives provided by ICMP that fulfil the above
mentioned criteria are of varying quality and scale. They cover the time of the first half of the 20th
century and were published in different coordinate reference systems (CRS). Table 1 gives an overview
of the properties of these maps.
Tab. 1: Properties of historical maps suitable for coastal area related analysis provided by ICMP.
Year Scale Ellipsoid / Spheroid Datum Projection
1903/04 1/100 000 Clarke ellipsoid no datum given Bonne 1923/24 1/100 000 Clarke ellipsoid no datum given Bonne 1951 1/100 000 Clarke ellipsoid no datum given Bonne 1953 1/100 000 Everest spheroid no datum given UTM 48N
In addition to the maps provided by ICMP, topographic maps of Vietnam published by the U.S. Army
Map Service were found in the internet (UNIVERSITY OF TEXAS LIBRARIES 2015a). After the USA got more
involved into the war in Vietnam they conducted mapping campaigns and published a new map series
(L7014) for the whole of Vietnam (DANG & LE 2001). They updated the old French topographic maps
supported by several aerial photography missions and increased the scale to 1/50 000. These maps
are the most accurate and detailed scanned maps used for this compilation.
The majority of the maps from this series displaying the area of the Mekong Delta are from 1965, but
some are from later years (see Tab. 2 for their properties). Few were updated last in the year 1989,
for which no older versions are available online anymore. One map displaying a part of Phú Quốc
Island is from 1957, while the map displaying the border between Vietnam and Cambodia is from
1993. The latter is the only map from the U.S. National Imagery and Mapping Agency, Series L7015,
Cambodia Topographic Maps (UNIVERSITY OF TEXAS LIBRARIES 2015b).
Tab. 2: Topographic maps of Vietnam from U.S. Army Map Service, Series L7014 (UNIVERSITY OF TEXAS LIBRARIES 2015a).
Year Scale Spheroid Datum Projection EPSG code Quantity
1957 1/50 000 Everest Indian 1960 UTM 48N 3148 1 1965 1/50 000 Everest Indian 1960 UTM 48N 3148 31 1969 1/50 000 Everest Indian 1960 UTM 48N 3148 3 1970 1/50 000 Everest Indian 1960 UTM 48N 3148 1 1989 1/50 000 WGS 84 WGS 84 UTM 48N 32648 3 1993 1/50 000 WGS 84 WGS 84 UTM 48N 32648 1
To ensure that geodata from different sources, and in the current case especially different times, can
be analysed and compared, it is necessary to use a common coordinate reference system (CRS).
Internationally the CRS usually used to exchange geodata is the geographic coordinate system WGS
84 (EPSG: 4326). For most of the other CRS, which are usually applied in regional mappings,
transformation algorithms into WGS 84 exist. Therefore WGS 84 is the CRS to choose to make geodata
available for as many users as possible.
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2.1. Processing of historical maps from the French colonial archives and map series L7014
Unfortunately, the old maps provided by ICMP lack information about the datum of the ellipsoid and
spheroid, which is necessary in order to georeference the scanned maps into their original CRS and
then transform them into WGS 84.
Therefore, the map series L7014 provided in GeoPDF format was processed first, and based on them
the older maps were georeferenced directly into WGS 84. The workflow of the georeferencing for the
map series L7014 is shown in table 3.
Tab. 3: Workflow for georeferencing map series L7014.
Processing step Example resulting file name
1 Download GeoPDF from UNIVERSITY OF TEXAS LIBRARIES 2015a tra_cu-6228-2.pdf 2 Save as Tiff file format using Adobe Photoshop tra_cu-6228-2.tif 3 Georeference into Indian 1960/UTM 48N or WGS84/UTM 48N,
depending on original CRS (see Tab. 2) using ESRI ArcGIS (define CRS to the Tiff files in ArcCatalog before using them in ArcGIS; transformation type ‘Adjust’; compression type ‘LZW’)
tra_cu-6228-2_.tif
4 Transform into WGS 84 using ESRI ArcGIS tool ‘Project Raster’ (transformation technique 2)
tra_cu-6228-2_WGS84.tif
5 Clip the surrounding borders (frame and legend) of the GeoTiff files (ArcToolbox -> Data Management Tools -> Raster -> Raster Processing -> Clip)
tra_cu-6228-2_WGS84_Clip.tif
The historical maps from the French colonial archives were georeferenced using QGIS. As reference
the maps from series L7014 were used in combination with Google Maps Satellite Images (OpenLayers
plugin for QGIS). When using the satellite images from Google the projects CRS in QGIS is automatically
set to WGS 84 / Pseudo Mercator (EPSG: 3857) and the additionally loaded map series L7014 is
automatically projected into the same CRS. Therefore the georeferencing results of the historical maps
from the French colonial archives were also in WGS 84 / Pseudo Mercator and had to be transformed
into WGS 84 with ESRI ArcGIS (see Tab. 4 for the workflow).
Tab. 4: Workflow georeferencing the historical maps from the French colonial archives.
Processing step Example resulting file name
1 Open .JP2 files and save them as tiff files (Adobe Photoshop) 237_100K_1904.tif 2 Crop maps to delete parts showing open sea (Photoshop) 237_100K_1904_.tif 3 Enhance imagery in Photoshop (colour, tone and saturation) 237_100K_1904__.tif 4 Georeferencing in QGIS based on map series L7014, file name
indicates the transformation type (Thin Plate Spline) and the number of ground control points (GCPs) used
237_100K_1904_TPS19.tif TPS = Thin Plate Spline 19 = number of GCPs
5 Transform into WGS 84 using ESRI ArcGIS 237_100K_1904_TPS19_WGS84.tif
The ground control points (GCPs) created for the georeferencing were saved as .points files (e.g.
237_100K_1904_GCP19.points). Therefore, the already cropped images (result step 2 in Tab. 4) can
be further enhanced in Adobe Photoshop if needed and then georeferenced again with a few clicks in
QGIS, as long as they are not cropped any further. Between 19 and 61 GCP were used to georeference
each map with a focus of the points in the coastal areas.
All historical maps which were georeferenced are now available in WGS 84. The Appendices I to IV
give an overview of the historical maps that were georeferenced. Before publishing they should be
projected into UTM 48N (WGS 84 / UTM 48N = EPSG: 32648).
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The georeferencing results of the historical maps are stored in the path
…\Coastal_Area_GIS_database\historical_maps\
Further details about the file system of the Coastal Area GIS database can be found on page 21.
Beside of the historical maps showing Ben Tre (236_100K_1903.tif and 236_100K_1953.tif) all
available maps from the French colonial archives were processed. Additionally, there are further
georeferenced historical maps covering Soc Trang Province. They are stored in the shoreline
geodatabase of Soc Trang Province created by Eberswalde University for Sustainable Development in
2013 (HNEE 2013a & 2013b).
2.2. Limitations
It needs to be mentioned that the map series L7014 is the most accurate in all terms. In comparison
to the older maps in particular the hydrological information is more accurate. In this regard especially
the maps from 1953 need to be handled carefully, because they suggest accuracy due to their detailed
content, but the georeferencing process showed a high degree of generalisation for the hydrological
map content.
The coastal areas, especially the coastline itself, between the map borders close to the border of Kien
Giang Province and Ca Mau Province, need to be considered inaccurate for all maps from the French
colonial archives (see Appendices I, II and III, between map tiles Kien Giang and Ca Mau West). The
same is the case for the maps from 1953 between the map tiles Ca Mau West and Ca Mau South (see
Appendix III).
3. Google Earth satellite images
The Google servers store a big collection of satellite images for the Mekong Delta region ranging for
some parts from the year 2000 till 2015 and are still getting updated. These images give good, and in
latest years also in high resolution, information about the development of the coastal areas. Still they
have to be treated carefully since their georeferencing is not always accurate (offsets of around 20 m
are possible). In comparison to this, the small offsets resulting from the manual georeferencing
process of exported Google Earth images (screenshots) can be neglected.
In general, the Google Earth maps can be divided into recent satellite images, usually shown when
using the Google Earth GUI, and the historical satellite images which are provided additionally.
Because Google chooses the date of the images shown in standard view based on their date as well
as their quality (e.g. cloud cover), some of the satellite images available in the timeline view are from
a more recent date than the usually shown ones.
The images from Google Earth are coming from two suppliers which hold the copyrights. For images
until the year 2013 this is DigitalGlobe, while the images since 2014 are from CNES/Astrium.
3.1. Recent images
The recent satellite images can be downloaded directly from the Google servers using the software
‘Google Satellite Maps Downloader’. It loads all the tiles stored for a chosen rectangular extend from
the Google servers and provides an option to combine the tiles into a single BMP file, which is already
georeferenced (CRS = WGS 84, EPSG: 4326). First, the bounding boxes coordinates were extracted
from Google Earth (GE settings: Decimal Degrees). They define the size and location of the area to be
downloaded. The resolution (zoom) chosen for the download was 18 and is therefore a compromise
between file size and resolution. The Google Servers limit the number of direct server accesses per
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day which also limits the application of this technique. The download of the images was therefore
spread over several days. Appendix V shows the downloaded recent satellite images in overview maps.
They are stored in the following path:
…\Coastal_Area_GIS_database\GE_images\recent_images\
Further details about the file system of the Coastal Area GIS database can be found on page 21.
3.2. Time series – historical satellite images
Since the beginning of this year the software ‘Google Earth Pro’ is available for free. It offers the
possibility to export images of the chosen view in high resolution. To make georeferencing of these
images easier and faster, the view in Google Earth Pro needs to be oriented north, not tilted and the
terrain needs to be switched off to eliminate vertical exaggeration which alters the images. For the
image export the eye altitude of the view was set to 2,000 m. Each exported image has a resolution
of 4800 x 3372 pixels.
Additionally, it is necessary to place three ground control points (GCPs) in three corners of the chosen
view area. The smaller their icon, the more accurate the georeferencing can be done (scale chosen
was 0.2). After exporting the image including the GCPs, the same image was exported again but the
GCPs were deactivated. Additionally the remaining available time steps from the timeline for the
chosen view (without GCPs) were exported.
In QGIS, the first image of each image set, which includes the GCPs, needed to be georeferenced. The
chosen transformation type was ‘linear’. The necessary coordinates were read from Google Earth Pro
in the properties of the GCPs (GE settings: Degrees, Minutes, Seconds). Usually the offset (residual) of
the GCPs in QGIS will be <0.5 pixel (1 pixel = 0.5 meter). If the residuals are higher, the orientation and
terrain settings in Google Earth Pro need to be checked. Finally the GCPs from QGIS were saved into
.point files and the worldfile of the extracted image created.
The other images which do not include the GCPs in the picture, but were exported without changing
the view in between, were georeferenced by loading the former .point file into the Georeferencer tool
of QGIS and applying it for all images of an image set.
With this method the historical satellite image sets of focus areas along the coast of the Mekong Delta
were exported from Google Earth Pro and georeferenced. They are available offline now. Appendix
VII shows an overview map of the areas for which all the available satellite image sets were
downloaded.
The path in the database where these files are stored is
…\Coastal_Area_GIS_database\GE_images\time_series\
Further details about the file system of the Coastal Area GIS database can be found on page 21.
3.3. Note about users licence for Google Earth imagery
Another important point which needs to be mentioned is the limited users licence from Google Earth
satellite images in case of publishing:
“Google does not own the imagery they display in Google Earth, and so cannot give
anyone else a licence to use that imagery for any purpose other than screenshots - which
may be used unaltered in commercial reports or presentations: i.e. single, static,
ungeoreferenced images retaining full attribution to Google and its suppliers.”
(STACKEXCHANGE.COM 2014).
“(…) You can use Google Earth Pro images and data for marketing purposes as long as this
data is not sold to any third parties. Additionally, the images must retain their copyright
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and source information. Images and videos used in on-air media require special approval.”
(STACKEXCHANGE.COM 2014).
Before publishing maps with satellite images in the background provided by Google it is necessary to
clarify licence issues. For further information see GOOGLE EARTH HELP (2015) and GOOGLE PERMISSIONS
(2015).
4. Geodata collection of already available data from GIZ offices
The GIZ offices in the provinces of the Mekong Delta acquired already different amounts of geodata
in the past. The data considered relevant for a coastal area related GIS database were collected. They
contain different information, depending on the former projects activities like shapefiles from
coastline mappings or land-use classifications. The files were stored in respective subfolders
depending on the corresponding province in the path …\Coastal_Area_GIS_database\provinces\
For Bac Lieu Province the folder contains one subfolder with maps (Agricultural Plan 2020, Forest
Development 2012 and Irrigation) in MapInfo as well as shape files and one subfolder containing single
shape files like coastlines of several years.
For Ca Mau Province the geadata available until now is limited to a compilation made by Petra
Gabelmann during an internship in the year 2013. It can be found in the respective folder.
For Kien Giang Province several maps are available containing recent data about forest distribution as
well as hydrological information. Additionally, a big collection of data was included into the database,
but the data was not yet further selected according to relevance for coastal area related programme
work (only the video files of a shoreline monitoring campaign were deleted due to their file size).
For Soc Trang Province, beside of the above mentioned historical shoreline database by HNEE, several
maps like mangrove forest plantation sites and land-use 2006 were included as well as separate shape
files of coastline monitoring and T-fence locations.
In addition, recent data for the whole Mekong Delta from the Southern Institute of Water Resource
Planning (SIWRP) and Sub-FIPI (Institute for Forest Inventory and Planning) should have been included
into the database. These datasets would be the best recent information available to conduct analyses
about changes in the coastal areas of the Mekong Delta in comparison to the historical files now
compiled. Unfortunately, it was not possible to get these data until now.
It is important to mention that data from partner institutions are often only available in MapInfo
format. These files can be read and edited in QGIS, but for wider usability the data should be converted
into shape files using the build in Universal Translator tool of MapInfo. Its advantage is the possibility
to convert the format in batch mode for complete folders. If a MapInfo license is not available this
conversion into .shp can also be made using QGIS. Therefore load the MapInfo file into the Layer view,
right click on the layer and save as ESRI Shapefile. The files provided from the GIZ offices of Kien Giang
and Bac Lieu were already processed.
Users also have to be careful because files from partner institutions usually are provided in the
coordinate reference system VN 2000 and therefore still need to be transformed (be aware that VN
2000 is different for each province). This is also the case for data converted into .shp file format. Until
now there is no instruction for this transformation issue available.
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5. Shoreline change analyses
Beside the creation of a coastal area related geodatabase, the aim of this consultancy was to obtain
knowledge about historical coastal regression and transgression along the coast of the Mekong Delta.
With the now available georeferenced historical maps and satellite images it is possible to examine
the historical changes along the coast (see Fig. 1)
Fig. 1: Coastline regression from 1904 until 2014 in eastern Ca Mau Province based on georeferenced historical maps and recent satellite images.
Shoreline change rates along transects covering big parts of the Delta were calculated using the ArcGIS
10 extension DSAS - Digital Shoreline Analysis System (U.S. GEOLOGICAL SURVEY 2015a). Additionally, the
absolute area change in hectare was calculated using ArcGIS. The Mekong river island Cu Lao Dung
was excluded from the analysis because it was already analysed before.
5.1. Shoreline change rates (DSAS)
The application of DSAS is described in detail in the ‘Installation Instructions and User Guide’, available
on the website of the U.S. Geological Survey (U.S. GEOLOGICAL SURVEY 2015b). In addition, MADORE 2014
provides a very good step by step manual for the complete DSAS workflow. Therefore, only a view
specific details will be presented here and not the complete workflow of the DSAS application. All files
related to the analyses of shoreline change rates are stored in the ArcGIS geodatabase
‘shorelines_mekong_delta.mdb’ stored under …\Coastal_Area_GIS_database\DSAS\
A general dataset with a collection of shorelines spanning the whole available time from 1903/04 till
2014/2015 and covering the complete Mekong Delta was created first for overview analyses.
Therefore the shorelines of the georeferenced historical maps from 1903/04, 1951/53 and the map
series L7014 were digitised. The maps from 1923/24 only differ from the 1903/04 maps in their areal
information like land use and hydrology, but have exactly the same shoreline as the older maps.
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Consequently, they were not digitised and excluded from analyses. In addition, the shorelines, defined
as the seaward vegetation border, of the recent Google Earth satellite images were digitised. All
digitisations were made in clockwise direction, which simplifies the use of several tools of ArcGIS.
For in depth analysis of several focus areas the additionally available historical satellite images from
Google Earth were also digitised and further expanded with already available shorelines from
shoreline monitoring surveys done by GIZ projects in Bac Lieu and Soc Trang as well as further digitised
historical maps from the Soc Trang geodatabase (HNEE 2013a).
Tab. 1 shows a list of all collected shorelines with their date and source. In total 70 shorelines were
collected and combined into the Feature Class ‘shorelines_all’.
Tab. 5: List of all collected and digitised shorelines.
The DSAS requires that the date is always given in a 10 digit code, e.g. 23/03/2011 (U.S. GEOLOGICAL
SURVEY 2015b). Therefore the dates of shorelines representing not a specific date but a year, as it is
the case for all the digitised maps as well as the GPS shoreline surveys from Bac Lieu, were set to the
1st of July of the corresponding year (see Tab. 5).
The baselines were cast along the coast of the whole Mekong Delta, mixed on- and offshore. For the
analysis of the whole delta a distance of 100 m between each transect was chosen, while the distance
was 50 m in the focus areas. For the focus area examination the baselines were altered to better follow
the chosen shorelines.
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At least two shorelines from different time steps are necessary to calculate change rates with the
DSAS, which offers several statistical calculation methods (U.S. GEOLOGICAL SURVEY 2015b). The most
frequent cited methods are EPR (end point rate) and LRR (linear regression) (THI et al. 2014). This is
because they are the least expecting for the data input. The EPR is calculated by dividing the distance
of shoreline movement by the time elapsed between the oldest and the most recent shoreline in
a given data set. Its major advantages are the ease of computation and minimal requirement of
only two shoreline dates. The major disadvantage is that in cases where more data are available,
the additional information is ignored (U.S. GEOLOGICAL SURVEY 2015b). This method was used for the
overview shoreline change rates between the data from map series L7014 and the most recent Google
Earth satellite images from 2014/15.
The LRR is the result of estimating the average rate of change using a number of shoreline positions
over time, with the change statistic of fitting a least-squared regression line to all shoreline points for
each transect. The linear regression rate is the slope of the line (THI et al. 2014). This method uses all
available data regardless of changes in trend or accuracy and is easy to employ. But it is susceptible
for outliers and tends to underestimate the rate of change relative to other statistics, like EPR
(U.S. GEOLOGICAL SURVEY 2015b). This method was used when more than two shorelines were available,
like in change rates from 1903/04 till 2014/15 as well as in analyses of focus areas. The calculation was
also commuted for the change rates from 1965 till 2014/15 for comparison with the EPR results. In
total 24 EPR and LRR calculations were made for varying areal and temporal extends.
5.2. Notes
While it is not possible to allocate values of accuracy for the old historical maps, it would be possible
for the Google Earth satellite images as well as for the map series L7014. Because of this, and because
both used calculation methods don’t use accuracy information during calculation, the accuracies of
the single shorelines were not taken into account in the conducted analyses. For further analyses of
the more recent data, for which accuracy can be allocated, other statistical methods like weighted
linear regression (WLR), can be used (U.S. GEOLOGICAL SURVEY 2015b).
Because the digitised shorelines from 1903/04 and 1951/53 are less accurate than the more recent
ones from the map series L7014 and Google Earth satellite images, the results calculated with them
need to be handled with caution. They are less exact than the results from the later shorelines and
can therefore only show a general trend for the shoreline movement.
Further satellite images to close the gap between the historical maps from 1965 and recent satellite
images exported from Google Earth can be obtained online (U.S. GEOLOGICAL SURVEY 2015c and GFIO
2015).
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5.3. DSAS – Results
The results of the DSAS are stored as maps in JPG and PDF file format are stored under
…\Coastal_Area_GIS_database\DSAS\_map_output
The corresponding ArcGIS 10.3 ArcMap document files have the same name like the exported maps
and are stored in the folder …\Coastal_Area_GIS_database\DSAS\
The advantage of the PDF files is the possibility to use the zoom function in which the vector data can
still be seen in detail, while the JPG files have resolution limitations.
Several calculation results based on the four main shoreline sets from 1903/04, 1951/53, L7014 (1965-
1993) and 2014/15 are presented in maps showing the whole Mekong Delta and southern Ca Mau:
DSAS_1904_2015 (DSAS_1904_2015_incl_transects) [using LRR]
DSAS_1965_2015 (…_incl_transects) [using EPR]
DSAS_MuiCaMau_EPR_1904_12015 (…_incl_transects)
DSAS_MuiCaMau_EPR_1965_2015 (…_incl_transects)
DSAS_MuiCaMau_LRR_1904_2015 (…_incl_transects)
DSAS_MuiCaMau_LRR_1904_2015_accretion (…_incl_transects)
DSAS_MuiCaMau_LRR_1904_2015_accretion_old (…_incl_transects)
Example maps are shown below in Fig. 2 and Fig. 3 for the LRR and EPR results of southern Ca Mau.
Fig. 2: Map ‘DSAS_MuiCaMau_LRR_1904_2015’ showing shoreline regression rates on the east coast and shoreline
transgression rates on the west coast of southern Ca Mau from 1903/04 till 2014/15.
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Fig. 3: Map ‘DSAS_MuiCaMau_EPR_1965_2015’ showing shoreline regression rates on the east coast and shoreline
transgression rates on the west coast of southern Ca Mau from 1965 till 2014/15.
For the following focus areas change rates were calculated including all available shorelines of the
examined area except for the ones labelled as unknown source and unknown definition in Tab. 5:
Border between the provinces Bac Lieu and Soc Trang (DSAS_FOCUS_BL_ST_...)
Border between the provinces Ca Mau and Bac Lieu (DSAS_FOCUS_CM_BL_...)
Along part of the coast of Kien Giang and Ca Mau (DSAS_FOCUS_KG_CM_...)
Nam Thai A Community in Kien Giang Province (DSAS_FOCUS_KG_NamThaiA_...)
Vinh Hai Region in Soc Trang Province (DSAS_FOCUS_ST_VinhHai_...)
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Exemplarily, Fig. 4 shows the results of the focus area Vinh Hai Region in Soc Trang Province with
regression rates of up to 25 m/yr and transgression rates of up to 83 m/yr from 2006 until 2015.
Fig. 4: Map ‘DSAS_FOCUS_ST_VinhHai_2006_20015_EPR_sat’ showing shoreline transgression and regression rates from 2006 till 2015 in Vinh Hai Region, Soc Trang Province.
Like mentioned before the conducted analyses are limited due to their areal extend. Even though for
the focus areas many extra shorelines were digitised based on Google Earth satellite images, these
timelines are discontinuous for long coastal stretches. This is exemplarily the case for the focus area
along the west coast of the provinces Ca Mau and Kien Giang. The discontinuity makes it difficult to
use LRR, even for parts of the coast where many shorelines are available. Consequently, the smaller
the examined area, the better the full potential of the DSAS can be used. Therefore it is recommended
to conduct further analyses of specific sites of interest with at most 15 km of coastline using the DSAS.
This would improve the results, for example at the erosion site in Ho Be Community, Vinh Hai Region,
Soc Trang Province (visible in the centre of Fig. 4). Additionally, the results could be better presented
in exported maps, especially when using JPG file format.
On the following pages the results for the west coast are presented. While it was possible to calculate
the change rates with LRR from 1965 till 2015 (see Fig. 5), for the recent shoreline change rates
calculated solely from satellite images based shorelines, only EPR could be used (see Fig. 6).
14
Fig. 5: Map ‘DSAS_FOCUS_KG_CM_1965_2015_LRR’ showing transgression rates of up to 52 m/yr and regression rates of
up to 10 m/yr from 1965 till 2015 along the west coast of the Mekong Delta.
15
Fig. 6: Map ‘DSAS_FOCUS_KG_CM_2001_2015_EPR’ showing transgression rates of up to 70 m/yr and regression rates of
up 32 m/yr between 2001 and 2015. But not along the whole coast the time spectrum of the shorelines is complete.
16
One focus area, which was completely excluded from the
analyses presented here, is the island Cu Lao Dung in Soc
Trang Province. A separate digital analysis about
shoreline change on this island was already carried out
by the author for the GIZ project ‘Management of
Natural Resources in the Coastal Zone of Soc Trang
Province’ using the shorelines from the historical
topographic maps from 1904 and 1965 as well as IKONOS
satellite images from 2012, all prepared by HNEE. For this
analysis, the coastline was defined as being the seaward
mangrove forest edge.
The main findings of the analysis are presented in the
map in Fig. 7 and were also published in SCHMITT & ALBERS
(2014). On Cu Lao Dung Island accretion rates are ranging
from 6.2 to 68.2 m per year over a period of 108 years
5.4. Shoreline area changes
For the calculation of the areal changes the collection of shorelines was used as well. Instead of using
the complete available dataset, only the three main sources were used, 1903/04, L7014 and 2014/15.
The shorelines were divided into three areas to simplify analysis and the presentation of the data. The
three areas in which the Mekong Delta was divided are Bac Lieu / Soc Trang, Kien Giang / Ca Mau and
southern Ca Mau. The northern part of Kien Giang Province, the island Cu Lao Dung in Soc Trang
Province as well as the provinces Tra Vinh and Ben Tre were not included in the analysis.
Before interpreting the results, it is necessary to mention that the coastline of 1903/04 is not very
accurate, while trustworthy results represent the numbers for the areal changes between map series
L7014 and 2014/15. Because of this, only for southern Ca Mau the areal change between 1903/04 and
1965 was calculated.
The working process includes the transformation of the polylines into polygons using the tool ‘Feature
to Polygon’ in the ArcToolbox. In the resulting shapefile all polygons smaller than 500 m2 (0.05 ha)
were deleted and the remaining ones used to calculate the areal changes. Each polygon was classified
manually into erosion and accretion. Out of these, only the biggest polygons were labelled with their
change values in the result maps.
The results of the areal change analysis are stored as maps in JPG and PDF file format in the folder
…\Coastal_Area_GIS_database\DSAS\_map_output
The corresponding ArcGIS 10.3 ArcMap document files have the same name like the exported maps
and are stored in the folder …\Coastal_Area_GIS_database\DSAS\
The same folder also contains the ArcGIS geodatabase ‘area_changes_mekong_delta.mdb’, which
holds all relevant data.
Fig. 7: Shoreline changes on Cu Lao Dung from 1904 till 2012. Base map provided by ESRI: DigitalGlobe 2008 & 2011, GeoEye 2000 & 2009 and i-cubed 1999 (own map, also published in SCHMITT & ALBERS 2014).
17
Maps
Here comes more text about the maps
18
19
The results of the calculations in hectare are shown in Tab. 6. While along the coasts of Bac Lieu / Soc
Trang and the west coast of Kien Giang /Ca Mau the transgression exceeded the regression from 1965
until 2015, more area was eroded than accumulated in southern Ca Mau. In total, 811 ha were
accreted along the examined coast of the Mekong Delta within 49 years. This figure would be even
higher if Cu Lao Dung and the other areas excluded from the analysis were to be included (see change
rates in these areas in the overview map on the cover of this report).
Tab. 6: Transgression and regression along the coast of the Mekong Delta provinces from 1965 till 2015 in ha.
maps transgression regression Sum
Bac Lieu / Soc Trang +3,005 -1,669 +1,336 Kien Giang / Ca Mau +2,349 -763 +1,586 Southern Ca Mau +10,540 -12,651 -2,111
Sum +15,893 -15,082 +811
The second map on the cover of this report includes the areal changes from 1904 until 1965 in
southern Ca Mau. Even though the results need to be handled with caution, it can be stated that the
total area lost within the last 49 years was almost half of the lost area within the 61 years before.
20
6. Conclusion and recommendations
The now available coastal area related GIS database contains a collection of georeferenced historical
maps from the French colonial archives, online sources and recent satellite image sets of the coastal
areas of the Mekong Delta. In addition, already digitised geodata from the provincial GIZ offices is
included.
The database therefore contains the material that is necessary to compile historical maps for a Coastal
Atlas of the Mekong Delta. However, the recent material, necessary for comparisons and analyses
about various developments in the coastal areas, still needs to be extended. To mention are especially
the recent data for the whole Mekong Delta from the Southern Institute of Water Resource Planning
(SIWRP) and Sub-FIPI (Institute for Forest Inventory and Planning). They should be included into the
database, because the data is necessary for comparisons and analyses with the now available
historical data.
Additionally, it is recommended to obtain further historical material or satellite images that close the
gap between the maps from 1965 and the recent satellite images from Google Earth. That applies for
the whole Mekong Delta area, including the historical shoreline database of Soc Trang Province.
Before maps containing satellite images exported from Google Earth are published, the licence issues
need to be addressed.
Furthermore, the MapInfo files seem to be in VN 2000 and therefore need to be transformed before
they can be used together with the other data now available (see chapter 4). The cooperation between
ICMP and Can Tho University might be an option to solve this issue. Alternatively, it would be possible
to contact Mr. Trịnh Hiệp (Deputy Head, Division of Planning and Finance, Department of Agriculture
and Rural Development of Soc Trang Province). He offered his support for this issue already on
previous occasion and provided the GIZ office in Soc Trang already in the past with the necessary PRJ
file to include VN 2000 into MapInfo (older datasets have the reference system altered manually).
At last, further analyses of small, specific areas of special interest can be examined for more accurate
results of shoreline change rates, especially recent changes including accuracy information, using the
DSAS
Roman Sorgenfrei November 2015
Geodata Management Advisor
21
Paths of stored data and structure
The complete coastal area related GIS database, called ‘Coastal_Area_GIS_database’, is stored on an
external hard drive. The file ‘Index_Coastal_Area_GIS_database.html’ contains a searchable index of
the complete content of the database.
The main folders of the database contain the DSAS
analysis results, the Google Earth satellite images
(‘GE_images’), the georeferenced historical maps
(‘historical maps’), the geodata of the Mekong Delta
provinces (‘provinces’), notes about the
transformation from VN 2000 into WGS 84 and file
conversion from MapInfo into shape file
(‘VN2000_to_WGS84’) as well as a working folder
containing the original maps from the French colonial
archives and additional historic maps
(‘working_folder’).
The folder ‘DSAS’ contains the ArcGIS databases for the shoreline
analyses as well as the ArcGIS 10.3 DSAS project files. The results
of the analyses are stored in the ‘_map_output’ folder. The
‘borders’ folder contains the administrative boundaries and
background literature as well as the ArcGIS DSAS software are
stored in the respective folders.
The ‘historical_maps’ folder contains several GIS project
files named ‘collection_historical_maps_all’ (for QGIS and
ArcGIS versions 9.3, 10.0 and 10.1) and a kmz file
container for Google Earth. The latter can be used in
Google Earth to get a fast overview of which maps are
available and the paths in which they are stored. The
‘_index’ folder contains index shapefiles while the
‘_map_output’ folder contains project files for several
maps in ArcGIS. The final results of the georeferencing of
the historical maps from the French colonial archives and
of map series L7014 is in the folder ‘WGS84’, sorted into
subfolders named after the year of the published maps
and their original CRS.
22
The folders containing the Google Earth satellite
images (‘recent_images’ and ‘time_series’) contain
similar additional material like the folder of the
historical maps (indices and maps), but the
georeferenced files were stored in subfolders
representing the part of the province they show (e.g.
BacLieuEast). The images of the time series are
further sorted into subfolders named after the date
of the satellite image (e.g. path:
…\Coastal_Area_GIS_database\GE_images\
time_series\CaMauEast\20021102\).
The geodata from the GIZ offices is stored in the
folder ‘provinces’ and is further divided into
folders for each province.
The maps which were provided in MapInfo file
format were saved under ‘[PROVINCE]_maps’
and the corresponding subfolders ‘MapInfo’ and
‘SHP’, the latter containing the converted shape
files.
The historical shoreline database of Soc Trang
Province can be found in the folder
‘CZMST_GIZ_HNEE_2013’.
The working folders contain the files for the single steps described above for the georeferencing of
the historical maps as well as the Google Earth satellite images. The maps from the French colonial
archives that were not yet georeferenced (north of Kien Giang Province and Soc Trang Province) are
also stored there as Tiff files.
23
One folder contains additional historical maps found in the internet, but none as detailed as the map
series L7014. The complete file collection from the French colonial archives is stored in folder
‘FrenchColonialArchives_byOlivier’.
24
References
Albers, T., Dinh, C. S. & K. Schmitt (2013): Shoreline Management Guidelines - Coastal Protection in
the Lower Mekong Delta.
Dang, H. V. & Q. T. Le (2001): Development of Surveying and Mapping Technoligy in Vietnam. –
<http://www.fig.net/resources/proceedings/fig_proceedings/korea/full-papers/pdf/session3/dang-
le.pdf> (accessed: 20.07.2015).
GFOI – Global Forest Observations Initiative (2015): Coordination of Satellite Data Supply. –
<http://www.gfoi.org/space-data/> (29.10.2015).
Google Earth Help (2015): Use of Google Earth Imagery. –
<https://support.google.com/earth/answer/21422?hl=en> (accessed: 31.07.2015).
Google Permissions (2015): Using Google Maps and Google Earth. –
<http://www.google.com/permissions/geoguidelines.html> (accessed: 31.07.2015).
HNEE – Hochschule für nachhaltige Entwicklung Eberswalde (2013a): Geodatabase ‘Historical
shoreline mapping of the southern Mekong Delta in Viet Nam’. –
<...\Coastal_Area_GIS_database\provinces\SocTrang\CZMST_GIZ_HNEE_2013\Shoreline_SocTrang>.
HNEE – Hochschule für nachhaltige Entwicklung Eberswalde (2013b): Report ‘Historical shoreline
mapping of the southern Mekong Delta in Viet Nam’. –
<...\Coastal_Area_GIS_database\provinces\SocTrang\CZMST_GIZ_HNEE_2013\GIZ_Geodatabase_Tr
aining_2013\report\REPORTCoastLineRegion_EN.pdf>.
Madore, B. (2014): Shoreline Change from a Storm Event Procedure using the Digital Shoreline
Analysis System. – <http://sandy.ccom.unh.edu/publications/library/Shoreline_change_procedural_
2014_11_18.pdf> (28.09.2015).
Schmitt, K. & T. Albers (2014): Area Coastal Protection and the Use of Bamboo Breakwaters in the
Mekong Delta. – In: Nguyen, D. T.; Takagi, H. & M. Esteban [eds.] (2014): Coastal Disasters and Climate
Change in Vietnam. Engineering and Planning Perspectives. 107-132. Amsterdam, Boston, Heidelberg.
StackExchange.com (2014): Answers to “Does a Google Earth Pro licence allow you to export geo-
referenced satellite images for use in other GIS software?”. –
<http://gis.stackexchange.com/questions/82632/does-a-google-earth-pro-licence-allow-you-to-
export-geo-referenced-satellite-ima> (accessed: 31.07.2015).
Thi, V. T., Xuan, A. T. T., Nguyen, H. P., Dahdouh-Guebas, F. & N. Koedam (2014): Application of remote
sensing and GIS for detection of long-term mangrove shoreline changes in Mui Ca Mau, Vietnam. –
Biogeosciences 11:3781-3795.
University of Texas Libraries (2015a): U.S. Army Map Service, Series L7014, Vietnam Topographic Maps
1/50 000. – <http://www.lib.utexas.edu/maps/topo/vietnam/> (accessed: 27.07.2015).
25
University of Texas Libraries (2015b): U.S. National Imagery and Mapping Agency, Series L7015,
Cambodia Topographic Maps 1/50 000. – <http://www.lib.utexas.edu/maps/topo/cambodia/>
(accessed: 17.09.2015).
U.S. Geological Survey (2015a): DSAS - Digital Shoreline Analysis System. Computer Software for
Calculating Shoreline Change. – <http://woodshole.er.usgs.gov/project-pages/DSAS/> (accessed:
26.07.2015).
U.S. Geological Survey (2015b): The Digital Shoreline Analysis System (DSAS) version 4.0 — an ArcGIS
Extension for Calculating Shoreline Change. – <http://woodshole.er.usgs.gov/project-
pages/DSAS/version4/index.html> (26.07.2015).
U.S. Geological Survey (2015c): EarthExplorer. – <http://earthexplorer.usgs.gov/> (29.10.2015).
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Appendices
Appendix I – Historical maps collection - 1904
27
Appendix II – Historical maps collection - 1924
28
Appendix III – Historical maps collection - 1953
29
Appendix VI – Historical maps collection - map series L7014
30
Appendix V – Google Earth Satellite Images - recent images (2014 & 2015)
31
Appendix VI – Google Earth Satellite images - recent images (folders)
Appendix VII – Google Earth Satellite Images - time series (folders)