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. 2010 Sep 14:9:45.
doi: 10.1186/1476-072X-9-45.

A high resolution spatial population database of Somalia for disease risk mapping

Affiliations

A high resolution spatial population database of Somalia for disease risk mapping

Catherine Linard et al. Int J Health Geogr. .

Abstract

Background: Millions of Somali have been deprived of basic health services due to the unstable political situation of their country. Attempts are being made to reconstruct the health sector, in particular to estimate the extent of infectious disease burden. However, any approach that requires the use of modelled disease rates requires reasonable information on population distribution. In a low-income country such as Somalia, population data are lacking, are of poor quality, or become outdated rapidly. Modelling methods are therefore needed for the production of contemporary and spatially detailed population data.

Results: Here land cover information derived from satellite imagery and existing settlement point datasets were used for the spatial reallocation of populations within census units. We used simple and semi-automated methods that can be implemented with free image processing software to produce an easily updatable gridded population dataset at 100 × 100 meters spatial resolution. The 2010 population dataset was matched to administrative population totals projected by the UN. Comparison tests between the new dataset and existing population datasets revealed important differences in population size distributions, and in population at risk of malaria estimates. These differences are particularly important in more densely populated areas and strongly depend on the settlement data used in the modelling approach.

Conclusions: The results show that it is possible to produce detailed, contemporary and easily updatable settlement and population distribution datasets of Somalia using existing data. The 2010 population dataset produced is freely available as a product of the AfriPop Project and can be downloaded from: http://www.afripop.org.

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Figures

Figure 1
Figure 1
Spatial distribution of P. falciparum malaria predictions stratified by endemicity class adapted from Hay et al. (2009) [2].
Figure 2
Figure 2
Population map showing numbers of people residing in each 100 × 100 metre grid square. Close-ups show detail around (a) Hargeisa, (b) Bosaso, and (c) Mogadishu.
Figure 3
Figure 3
Comparison of Somalia gridded population datasets. (a) Newly created population dataset (AfriPop) showing 2009 population numbers in each 100 × 100 metre grid square; (b) close-up of the AfriPop dataset showing detail around Hargeisa; (c) close-up of the AfriPop dataset showing detail around Mogadishu. (d) LandScan 2008 population numbers in each 1 × 1 km grid square [21]; (e) close-up of the LandScan dataset showing detail around Hargeisa (f) Close-up of the LandScan dataset showing detail around Mogadishu. (g) Global Rural Urban Mapping Project (GRUMP) showing 2009 population numbers in each 1 × 1 km grid square [22]; (h) close-up of the GRUMP dataset showing detail around Hargeisa (i) close-up of the GRUMP dataset showing detail around Mogadishu.
Figure 4
Figure 4
Differences in population counts per district for the year 2005 (%). (a) Difference between UNDP estimates and LandScan estimates, (b) Difference between UNDP estimates and GRUMP estimates.
Figure 5
Figure 5
Per-pixel absolute differences between population datasets. (a,b,c) Differences between AfriPop and LandScan, and (d,e,f) Differences between AfriPop and GRUMP. Close-ups show detail around the capital Mogadishu (b,e) and the Northern part of the Shabelle river (c,f).
Figure 6
Figure 6
Absolute differences between population datasets plotted against the AfriPop values.
Figure 7
Figure 7
Population at risk of Plasmodium falciparum in Somalia in 2007 according to different population datasets.

References

    1. UNHCR Somalia. http://www.unhcr.org/cgi-in/texis/vtx/page?page=49e483ad6
    1. Hay SI, Guerra CA, Gething PW, Patil AP, Tatem AJ, Noor AM, Kabaria CW, Manh BH, Elyazar IRF, Brooker S, Smith DL, Moyeed RA, Snow RW. A world malaria map: Plasmodium falciparum endemicity in 2007. PLOS Medicine. 2009;6(3):e48. doi: 10.1371/journal.pmed.1000048. - DOI - PMC - PubMed
    1. Dobson JE, Bright EA, Coleman PR, Durfee RC, Worley BA. LandScan: a global population database for estimating populations at risk. Photogrammetric Engineering and Remote Sensing. 2000;66:849–857.
    1. Bhaduri B, Bright E, Coleman P, Dobson J. LandScan: Locating people is what matters. Geoinformatics. 2002;5:34–37.
    1. Hay SI, Noor AM, Nelson A, Tatem AJ. The accuracy of human population maps for public health application. Tropical Medicine & International Health. 2005;10:1073. - PMC - PubMed

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