WikiProject Mali

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Mali, Africa
Latitude: (17, Longitude: -3.2
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Mali is a Country in Africa at latitude 17° 0′ 0″ North, longitude 3° 12′ 0″ West.

Map of Mali

Mali is a country in Africa. Mapping of Mali is still in very early stages. Almost no gps tracks exist for this region, however high resolution Bing imagery coverage was recently extended to cover most of the country ([1])

Things that are done

Cities and villages
Highways
  • Hopefully most of the major highways are mapped. Some of them even have gps tracks as a source.
  • The VMAP0 dataset is imported in the openstreetmap database, the accuracy of the data is not very good, but it is a start. The highways are tagged as "road" and fixme=check import. Now that bing imagery is available over most of Mali, mappers may decide to erase entirely these ways if they do not correspond to roads in the vicinity. And you can simply trace roads with the new imagery. Spotting roads is still quite a sketchy process. Reportedly some visible tracks across the landscape may be the result of a single vehicle driving there (because of the way the ground surface cracks). Clearly we'd prefer to get some people with local knowledge survey and clarify all these roads ...but for now it's fairly safe to assume that none of that is happening! (Anyone doing this, let us know! And add source=GPS tags all over your data)
Rivers

There's lots of river courses visible in imagery, many of which are seasonally dried up (often dried up in the imagery). We need to think twice before mapping everything we see.

  • Niger river from Tombouctou area to the Niger border.
  • coastlines
  • islands
  • residential areas
Other

Potential datasources

  • GNS data
  • vmap0 data (road data is imported)
  • Starting in june 2012, there is new high resolution Bing imagery in particular along the Niger river from Tombouctou area to the Niger border.
  • ...

People contributing to the river Niger

People contributing to roads

People contributing to border

External links

Find and fix errors reported

Imagery

About the imagery

Pnorman (talk) is hosting some 2012 multi-spectral Landsat imagery of the Niger river. JOSM will suggest the standard colour imagery, but other is available. All imagery is 15m/px.

Although there is Bing high resolution imagery for much of central Mali and Bing will fall back on a landsat layer if there is no highres available for an area, the Bing imagery suffers from two major limitations that cause problems for mapping in the Inner Niger Delta. First, the images are a single point in time, which doesn't show the variable nature of the Niger floodplain well, and second, the imagery is all taken in the visible light frequencies of the color spectrum, which show a good picture of the area for tracing roads and buildings, but are less useful for understanding the vegetaion growth cycle in this area.

In order to address these two shortcomings for the Niger Inner Delta area, pnorman has produced the following image layers composed of 15 m/pixel pansharpened images which are taken from the LandSat satellite. The images show the following different points in time to illustrate the annual flood cycle of the delta:

  • March 2010 - Taken nearing the end of the dry season when the water is near its low point and vegetation is mostly dead.
  • October 2012 - Taken at the peak of the flood season when the water is near its maximum and vegetaion is thriving.

Although normally we work with normal visible light pictures, the landsat satellite actually takes images in 7 different color bands (3 in visible, and 5 in infrared, two of which are duplicates). A color RGB image is composed from these images by choosing 3 color bands (one each for the red, green, and blue channels of the final image). The image is then sharpened using a higher-resolution band to increase the resolution to 15m/px. A description of the bands, what they show, and what combinations are normally used is available here. For the mapping of the delta region, we have chosen 3 different color combinations for each of the 2 points in time described above, for a total of 6 imagery layers. The color combinations chosen are listed below (the numbers represent the bands chosen for the RGB layers in the image respectively.

  • 321 - The 'natural color' layer showing the image in visible light (the red, green, and blue channels in the layer just show normal red, green, and blue). This layer will help you get a sense of what the area looks like so you can understand how to interpret the colors in the other layers.
  • 432 - 'near infrared' layer which shows vegetation in red, and bare soil in brown. Deep red hues indicate broad leaf and/or healthier vegetation while lighter reds signify grasslands or sparsely vegetated areas.
  • 742 - 'far infrared' a relatively normal looking image, even though it is showing mostly infrared. Healthy vegetation is shown in bright green, grasslands will appear green, pink areas represent barren soil, and oranges and browns represent sparsely vegetated areas. Dry vegetation will be orange and water will be deep blue, even if it is muddy and low-contrast on visible light images.

How to use this imagery

The ideal way to use this imagery is as a 'double check' on mapping done from the high resolution Bing imagery. Generally you will want to map some feature on the ground from the Bing imagery with a detailed and nicely positioned way traced from that, and then you will flip to displaying one of pnorman's imagery layers to set the type of the feature, or to see if it grows or shrinks as the water advances and retreats. For example some areas completely flood during the peak of the flood but then drain out as the water recedes. Other areas, like the main river channels, stay flooded year around. It is recommended to use JOSM for this work since the layers can easily be turned on and off or shown in a transparent fashion to "mix" the available imagery. Also, you might want to align the individual imagery layers to make it easier for you to compare features from one layer to the next, but this is not terribly important since all traced objects should be aligned to the Bing high res layer.

Imagery table

Thumbnail Layer Preview Max zoom JOSM URL P2 URL
Niger Delta Oct 2012 321.png Niger Oct 2012 321 bands 13 http://pnorman.dev.openstreetmap.org/imagery/niger_oct_2012_321/{zoom}/{x}/{y}.png

Load in JOSM

http://pnorman.dev.openstreetmap.org/imagery/niger_oct_2012_321/$z/$x/$y.png
Niger Delta Oct 2012 432.png Niger Oct 2012 432 bands 13 http://pnorman.dev.openstreetmap.org/imagery/niger_oct_2012_432/{zoom}/{x}/{y}.png

Load in JOSM

http://pnorman.dev.openstreetmap.org/imagery/niger_oct_2012_432/$z/$x/$y.png
Niger Delta Oct 2012 742.png Niger Oct 2012 742 bands 13 http://pnorman.dev.openstreetmap.org/imagery/niger_oct_2012_742/{zoom}/{x}/{y}.png

Load in JOSM

http://pnorman.dev.openstreetmap.org/imagery/niger_oct_2012_742/$z/$x/$y.png
- Niger Mar 2010 321 bands 13 http://pnorman.dev.openstreetmap.org/imagery/niger_mar_2010_321/{zoom}/{x}/{y}.png

Load in JOSM

http://pnorman.dev.openstreetmap.org/imagery/niger_mar_2010_321/$z/$x/$y.png
- Niger Mar 2010 432 bands 13 http://pnorman.dev.openstreetmap.org/imagery/niger_mar_2010_432/{zoom}/{x}/{y}.png

Load in JOSM

http://pnorman.dev.openstreetmap.org/imagery/niger_mar_2010_432/$z/$x/$y.png
- Niger Mar 2010 742 bands 13 http://pnorman.dev.openstreetmap.org/imagery/niger_mar_2010_742/{zoom}/{x}/{y}.png

Load in JOSM

http://pnorman.dev.openstreetmap.org/imagery/niger_mar_2010_742/$z/$x/$y.png


Although most users do not care about the landsat scenes chosen, they might be useful

Imagery set Scenes
Niger Oct 2012 LE71970502012304ASN00
LE71970492012304ASN01
LE71980502012279ASN00
LE71960502012297ASN00
LE71980492012327ASN00
LE71960492012297ASN00