Monitoring changes in the Menik Farm IDP camps in Sri Lanka using multi-temporal very high-resolution satellite data

Figures & data

Figure 1.  Location of the Menik Farm IDP camp in Vavuniya district, Sri Lanka.

Table 1. List for very high-resolution satellites used in the analysis.

Satellite	Spatial resolution (m)	Spectral resolution	Launch year
WorldView-1	0.5 PAN	1 PAN	2007
GeoEye-1	0.5 PAN, 1.65 MS	1 PAN, 4 MS	2008

Table 2. Acquisition details for WorldView-1 and GeoEye-1 data.

Satellite	Date	Time (GMT)	Sun azimuth	Sun elevation
WorldView-1	26 June 2009	05:24	49.3	66.3
GeoEye-1	28 February 2010	05:14	124.2	60.8
Stereo data		05:15	124.4	60.9

Figure 2.  A sample of elongated camp structures. WorldView-1 imagery © Digitalglobe 2009, distributed by e-GEOS.

Figure 3.  A sample of tents located inside Menik Farm IDP camp. WorldView-1 imagery © Digitalglobe 2009, distributed by e-GEOS.

Figure 4.  Presentation of the path's net constructed inside a Menik Farm IDP camp. WorldView-1 imagery © Digitalglobe 2009, distributed by e-GEOS.

Figure 5.  Presentation of the random selected samples within Menik Farm IDP Camp. WorldView-1 imagery © Digitalglobe 2009, distributed by e-GEOS.

Figure 6.  A randomly selected cell with tents marked as points in a visual interpretation process. WorldView-1 imagery © Digitalglobe 2009, distributed by e-GEOS.

Figure 7.  Randomly selected cell with tents extracted automatically and converted into the centroids.

Table 3. Comparison of the number of tents derived from automatic analysis and from visual interpretation. Assessment based on satellite image acquired on 26 June 2009.

Camp section	Automatic extraction	Visual interpretation	Difference (absolute)	Difference (percent)	No. of sampling cells
Zone 0	74	69	+5	7.25	39
Zone 1	99	91	+8	8.79	17
Zone 2	387	406	−19	−4.68	34
Zone 3	210	217	−7	−3.23	16
Zone 4	294	296	−2	−0.68	37
Zone 5	41	40	+1	2.50	9
Total	1105	1119	−14	−1.25	152

Table 4. Number of tents automatically extracted per each camp's zone. Analysis based on satellite image acquired on 26 June 2009 (WorldView-1).

Camp section	No. of tents
Zone 0	1503
Zone 1	1932
Zone 2	6951
Zone 3	6930
Zone 4	6104
Zone 5	1730
Total	25,150

Figure 8.  Comparison of results from visual interpretation and automated enumeration based on 152 randomly selected cells.

Figure 9.  Menik Farm – Zone 2. Example of the structures’ appearance detected correctly: pre-image (left) and post-image (right). WorldView-1 imagery © Digitalglobe 2009 and GeoEye-1 imagery © GeoEye 2010, both distributed by e-GEOS.

Figure 10.  Menik Farm – Zone 4. Example of the structures’ appearance detected correctly: pre-image (left) and post-image (right). WorldView-1 imagery © Digitalglobe 2009 and GeoEye-1 imagery © GeoEye 2010, both distributed by e-GEOS.

Figure 11.  Menik Farm – Zone 4. Example of the disappearance of the structures detected correctly: pre-image (left) and post-image (right). WorldView-1 imagery © Digitalglobe 2009 and GeoEye-1 imagery © GeoEye 2010, both distributed by e-GEOS.

Figure 12.  Menik Farm – Zone 3. Example of the disappearance of the structures detected correctly: pre-image (left) and post-image (right). WorldView-1 imagery © Digitalglobe 2009 and GeoEye-1 imagery © GeoEye 2010, both distributed by e-GEOS.

Table 5. Results’ summary for change detection analysis. The area with new structures detected on a satellite image acquired on 28 February 2010 (GeoEye-1) and not visible on a satellite image acquired on 26 June 2006 (WorldView-1).

	Pre-situation	Appearance	%
Area (m^2)	8,792,212	153,768	1.7
No. of structures	25,149

Table 6. Results’ summary for change detection analysis. The area with structures and number of structures detected on a satellite image acquired on 26 June 2009 (WorldView-1) and not visible on a satellite image acquired on 28 February 2010 (GeoEye-1).

	Pre-situation	Disappearance	%
Area (m^2)	8,792,212	433,840	4.9
No. of structures	25,150	3,813	15.2