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| Senegal Land Cover Mapping |
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Within the West Africa programme of GLCN, the land cover mapping
of Senegal was carried out. The initiative, coordinated by GLCN staff,
but conducted in collaboration with local institutions and experts,
took place mainly in the GLCN office at Centre de Suivi Ecologique (C.S.E.),
in Dakar (Senegal). Some activities were instead conducted at GLCN
Land Cover Topic Center office in Florence (Italy).
Major outputs of the initiative are:
- full resolution and aggregated land cover database (2005)
- mapping accuracy assessment
- land cover change analysis (1990/2005)
- local capacity building
1. Land Cover Database (2005)
The development of the land cover database is based on the multi-phase
image interpretation approach, which is successfully adopted by FAO
in a number of projects.
The visual interpretation of Landsat ETM 2005 satellite images was
carried out using GeoVIS
software, a vector-based editing system specifically designed
for thematic interpretation. The photo-interpretation mapping scale
was 1:100,000. 55 LCCS classes were identified and used as legend to
interpret satellite imagery.
The GLCN methodology requires a field verification campaign to validate the interpretation.
171 field verification forms have been compiled and 706 field extra
observations (GPS coordinates, a photo and a short description/code for each point)
were carried out.
The final full resolution dataset consists of 23,922 polygons, covering
an area of 19,659 thousands ha. FAO data distribution policy requires
the creation of an aggregated dataset on the basis of a spatial criteria,
which produces about the 11% reduction of the total amount of polygons.
The spatially aggregated dataset (available for download) consists of
21,238 polygons.
The Senegal land cover database was also processed by the GLCN's Vedas
(Vegetation Dynamic Assessment) software to extrapolate eco-climatic
information. Vedas was first tested with success in 2007 on East Africa data.
In 2008, the Vedas procedure was applied on Senegal with Modis 005
remote sensed vegetation data (250 mt resolution – 16 days period)
and with Spot vegetation data (1 km resolution – 10 day period).
Summarizing, the average NDVI values (calculated in the 2001-2007
period for MODIS, and 1999-2006 period for Spot) was extracted for
each polygon of the Senegal land cover dataset, providing consistent
spatial and temporal comparisons of the vegetation conditions and
monitoring vegetation activity in support of phenologic, change
detection and biophysical interpretations.
NDVI profiles of different land cover classes can differ in mean
values but tend to have a similar shape linked to the seasonality
of local vegetation.
| Id |
Title |
Type |
Download |
| 1.a |
Land Cover Mapping Report |
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3.79 MB |
| 1.b |
Land Cover Classes Description |
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16.85 MB |
| 1.c |
Legend details (English and French) |
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0.85 MB |
| 1.d |
Aggregated vs Full Resolution database: aggregation criteria |
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0.18 MB |
| 1.e |
Metadata and GIS data download (FAO's Geonetwork) |
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web link |
| 1.f |
Testing Vedas procedure on Senegal Land Cover Database: reports |
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0.31 MB |
| 1.g |
Senegal Land Cover Mapping Overview presentation |
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11.02 MB |
| 1.h |
Senegal Land Cover Classes Description presentation |
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58.26 MB |
2. Mapping Accuracy Assessment
Through the GLCN's Mapping
Accuracy Program (MAP), an Accuracy Statistical Report was generated.
For each one of the 477 polygon randomly extracted, all the information
collected in the assessment phase were stored and elaborated by the
software. The results of this assessment was used to identify classes
showing a low rate of accuracy and revise their interpretation.
| Id |
Title |
Type |
Download |
| 2.a |
ANNEX 1 – Accuracy Assessment Statistical Report |
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1.76 MB |
| 2.b |
Senegal Accuracy Assessment and Statistics |
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2.95 MB |
3. Land Cover Change Analysis
Within the Land Degradation Assessment in Drylands (LADA) framework, an
analysis of land cover changes in Senegal was carried out.
[Details..]
| Id |
Title |
Type |
Download |
| 3.a |
GLCN - LADA: Land Cover Change Report, 1990-2005 |
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1.41 MB |
| 3.b |
Senegal Land Cover Change Assessment |
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5.41 MB |
| 3.c |
MADCAT-based Land Cover Change Basic Report |
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0.65 MB |
| 3.d |
MADCAT-based Land Cover Change Extended Report |
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3.68 MB |
4. Local Capacity Building
Capacity building was one important aspect of this project since it
assures long term sustainability of the activity. The local technical
staff involved in the project received regular training during the
different phases, resulting in highly experienced image analysts.
Furthermore, they became skilled in using GLCN's software and
methodologies, which is fundamental for future updates of Senegal's
land cover.
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