Baseline data assessment and report for Chad camps

Baseline data assessment and report for Chad camps#

Quantitative assessment of OpenStreetMap (OSM) completeness#

The OSM completeness of buildings and highways data is different in each of the refugee camps:

3 camps had high coverage of buildings and highways
15 camps have partial or low coverage of buildings and highways
4 camps did not have data of buildings and highways.

Although 3 camps had high data coverage, the baseline data assessment showed us that approximately 70% of the data has low quality, due to a) mismatch between the data and the baseline satellite imagery or b) the buildings were mapped with old imagery and need to be re-aligned.

_images/chad_camp_img1.png — Fig. 37 Buildings and highways that need to be aligned to the Maxar Premiun imagery (most current imagery in this location)#

Some other issues that need to be fixed are; misaligned highways, inaccurate buildings and highways, etc.

Misaligned highways

_images/chad_camp_img2.png — Fig. 38 Misaligned highways#

Misaligned and inaccurate buildings

_images/chad_camp_img3.png — Fig. 39 Misaligned and inaccurate buildings#

The tables below (table 1 and table 2) summarize the method for our assessment of data quality and coverage

Levels	Description
High	Approximately more than 70% of buildings/highways were mapped
Partial	Approximately between 30% - 70% of buildings/highways were mapped
Low	Approximately less that 30% of buildings/highways were mapped
Nothing	None building/highway mapped

Table 1: OSM data coverage levels

Levels	Description
Good	Buildings/highways mapped match with the current imagery and have the correct shape.
Medium	Some areas of the refuge have buildings/highways with good quality and other areas have buildings/highways with low quality.
Low	Buildings/highways mapped do not match with the current imagery, have wrong shape, several buildings were mapped as only one building, and the data has different issues that need to be fixed.

Table 2: OSM data quality levels

According to the summary table of data quality (table 3), there are 3 camps without buildings, 8 camps with less than 500 buildings and 11 camps with more than a thousand buildings. Concerning highways, there is 1 refuge without highways mapped, 14 camps with less than 30 km of highways, and 7 camps with more than 36 km of highways.

N°	Camps	OSM data coverage	OSM data quality	Total buildings	Total highway Length
1	Amboko Camp	Buildings: Partial Highways: High	Buildings: Low Highways: Low	1,813	8.051 km
2	Amnabak	Buildings: Low Highways: Low	Buildings: Medium Highways: -	398	1.472 km
3	Belom	Buildings: Partial Highways: High	Buildings: Medium Highways: Medium	4,450	27.338 km
4	Bredjing Camp	Buildings: Low Highways: Low	Buildings: Low Highways: Low	34	14.743 km
5	Daha 1 Village	Buildings: Low Highways: Low	Buildings: Low Highways: Medium	222	6.035 km
6	Dembo	Buildings: Partial Highways: High	Buildings: Low Highways: Low	2,324	41.02 km
7	Diba Village	Buildings: Nothing Highways: Low	Buildings: - Highways: Medium	0	0.455 km
8	Djabal Camp	Buildings: Partial Highways: High	Buildings: Medium Highways: Medium	4,884	49.163 km
9	Doholo Camp	Buildings: High Highways: Low	Buildings: Good Highways: Medium	2,037	3.314 km
10	Dosseye Camp	Buildings: Partial Highways: Partial	Buildings: Low Highways: Low	1,503	36.14 km
11	Farchana	Buildings: Low Highways: Partial	Buildings: Low Highways: Low	7	37.94 km
12	Gaga Camp	Buildings: Low Highways: Low	Buildings: Low Highways: Low	18	13.735 km
13	Gondje Camp	Buildings: Partial Highways: High	Buildings: Low Highways: Low	1,168	38.339 km
14	Goz Amir Camp	Buildings: Low Highways: Low	Buildings: Low Highways: Low	133	25.83 km
15	Iridimi	Buildings: High Highways: High	Buildings: Good Highways: Medium	8,213	20.555 km
16	Kounoungou Camp	Buildings: Low Highways: Low	Buildings: Low Highways: Low	34	7.95 km
17	Mile Camp	Buildings: High Highways: Partial	Buildings: Medium Highways: Low	5,343	21.314 km
18	Moyo	Buildings: Low Highways: Nothing	Buildings: Low Highways: -	7	0.0 km
19	Oure Cassoni Camp	Buildings: High Highways: High	Buildings: Low Highways: Low	8,623	37.673 km
20	Touloum	Buildings: High Highways: High	Buildings: Medium Highways: Medium	7,832	53.97 km
21	Treguine Camp	Buildings: Nothing Highways: Partial	Buildings: - Highways: Medium	0	19.522 km
22	Vom village	Buildings: Nothing Highways: Low	Buildings: - Highways: Low	0	1.909 km

Table 3: Summary per refuge of the OSM data completeness

Quality and currency of available imagery in base maps#

There are different satellite imagery basemaps available in the JOSM editor for the mapping process; Bing aerial imagery, Esri World Imagery, ESRI Clarity, Maxar Premium, Mapbox Satellite. From the baseline data assessment, we found that the imageries most used in the previous mappings were Maxar Premium and Bing aerial imagery.

The dates of the images are unknown, so to know which of them is the most current, we did a comparison between them and one of the signs that one imagery is the most recent is that it shows buildings and/or highways in areas where the other imagery only shows an empty field.

Old imagery

_images/chad_camp_img4.png — Fig. 40 Bing aerial imagery (old imagery)#

New imagery

_images/chad_camp_img5.png — Fig. 41 Maxar premium (current imagery)#

In most cases the baseline OSM data aligned with Bing imagery, but since the most current imagery in almost all camps is Maxar, we are going to align the existing data to Maxar.

Levels	Description
High	Imagery does not loses its resolution
Medium	Imagery loses its resolution but we can differentiate the buildings and highways for mapping
Low	Imagery loses its resolution but is difficult to differentiate the buildings for mapping

Table 4: Imagery quality levels were classified according to their resolution

N°	Camps	Most current imagery	Imagery quality
1	Amboko Camp	Maxar Premium	Medium
2	Amnabak	Maxar Premium	Low
3	Belom	Maxar Premium	Low
4	Bredjing Camp	Maxar Premium	Low
5	Daha 1 Village	Bing Aerial	Medium
6	Dembo	Maxar Premium	Low
7	Diba Village	Maxar Premium	Low
8	Djabal Camp	Maxar Premium	Low
9	Doholo Camp	Maxar Premium	Medium
10	Dosseye Camp	Maxar Premium	Medium
11	Farchana	Maxar Premium	Low
12	Gaga Camp	Maxar Premium	Low
13	Gondje Camp	Maxar Premium	Medium
14	Goz Amir Camp	Maxar Premium	Low
15	Iridimi	Maxar Premium	Low
16	Kounoungou Camp	Maxar Premium	Low
17	Mile Camp	Maxar Premium	Low
18	Moyo	Maxar Premium	Low
19	Oure Cassoni Camp	Maxar Premium	Low
20	Touloum	Maxar Premium	Low
21	Treguine Camp	Maxar Premium	Low
22	Vom village	Maxar Premium	Low

Table 5: Summary per refuge of the most current imagery and its quality

According to table 5, most camps have poor quality imagery, so in total there are 17 camps with poor quality imagery and 5 camps with medium quality imagery. And the most current imagery is Maxar Premium.