|
|
|
Remote Sensing and GIS for Good Governance: Analysis of High Spatial Resolution Ikonos Imagery for Surveying Agricultural activities in the city of Ouagadougou, Burkina Faso
Ilona Kemeling
Laboratory for Geo-information and Remote Sensing, Wageningen University
P.O. Box 47, 6700 AA Wageningen, The Netherlands
Tel: +31317 474 640; Fax: +31317 474 567;
Email: Ilona.Kemeling@Student.GIRS.WAU.NL
Steven M. de Jong & Pieter B.M. van Teeffelen
Faculty of Geographical Sciences, Utrecht University
P.O. Box 80.115, 3508 TC Utrecht The Netherlands
Tel: +3130 253 2749; Fax: +3130 253 1145;
Email: s.dejong@geog.uu.nl
Leo M. van den Berg & Gerbert J.Roerink
Alterra, Wageningen University & Reseacrh Centre
P.O. Box 47, 6700 AA Wageningen, The Netherlands
Email: l.m.vandenberg@alterra.wag-ur.nl,
G.J.Roerink@Alterra.wag-ur.nl
Abstract
In West African cities, urban and peri-urban agricultural activities form a major economic activity for
a significant group of inhabitants. Intensive and commercial-oriented horticulture is one of the most
important activities in the cities such as Ouagadougou and Bamako. Horticulture activities form a
fragile balance with waste management (city waste is used as manure for horticulture) and with other
agricultural activities such as livestock raising. Local governments consider these agricultural
activities as a loss of valuable city-space and often deny their economic importance. Consequently,
horticulturists located within the city are often forced to stop their activities or to relocate their
business to the urban fringe or beyond. Unfortunately, no well-organised resettlement programmes for
these activities exist in the West African countries. The government does often not recognise the
importance of such programmes due to a lack of awareness of the importance of horticultural
activities in the cities as a widespread economic activity, in combination with city waste recycling.
Often no reliable information is available on the extent of the horticultural activities in the city.
One of the objectives of this study is to use high-resolution satellite images to survey the agricultural
activities in the cities and to use time-series of images to determine the spatial dynamics of these
activities. Only since 1999, satellite images are available at a resolution of 1 to 4 m potentially
enabling us to monitor these small scale agricultural lots. Previous available images (SPOT-XS and
Landsat TM) having pixels of 20 meters or more do not provide sufficient detail to map these
activities properly. In this study we investigated the value of high spatial resolution IKONOS imagery
to survey agricultural activities within the city and at the urban fringe. IKONOS has a pixel size of 4
by 4 meters and has 4 spectral bands: blue, green, red and near infrared. Traditional spectral
classification methods, based on ground truth sets and spectral differences between the crops, failed to
identify individual activities. This was due to spectral overlap of the thematic land cover types. The
agricultural activities occur mainly near water bodies because of irrigation requirements and near
roads (pistes) to facilitate transport. Adding this type of GIS stored information to the classification
process improved the results considerably.
|
|
|