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The accessibility indicated as travel time is calculated using the cost-distance function of ArcGIS by defining source features (features from where the travel time is calculated) and a cost raster (each pixel indicates the amount of time needed to cross it). The choice of source features depends on the scope of the accessibility map and is in this layer the capital Addis Abeba. To calculate the cost raster we basically include all the available spatial data of a given extent that can in some way affect the travel speed of humans. This includes things that can make us travel faster (e.g. roads), but also things that serve as brake (e.g. slopes, waterbodies) or even barriers (e.g borders). When preparing the cost raster one also needs to consider which means of transportation are available to the people that we represent in the accessibility map. Usually it is assumed that the people use the fastest means of transportation. This means travelling by car or bus on the road and on foot when off-road.
Input layers used
• Land cover (obtained from WLRC) to define the travel speed off-road (e.g. less vegetated areas allow for a faster pace than densely vegetated areas)
• Roads/infrastructure (EthioGIS II) to define the travel speed using public transport depending on the road/infrastructure type
• Slope (ASTERDEM) to reduce the travel speed with increasing slope
• Rivers and water bodies (EthioGIS II) to reduce the travel speed when no bridge / ferry is available (rivers and water bodies are not considered as transportation routes) |
| summary:
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The accessibility indicated as travel time is calculated using the cost-distance function of ArcGIS by defining source features (features from where the travel time is calculated) and a cost raster (each pixel indicates the amount of time needed to cross it). The choice of source features depends on the scope of the accessibility map and is in this layer the capital Addis Abeba. To calculate the cost raster we basically include all the available spatial data of a given extent that can in some way affect the travel speed of humans. This includes things that can make us travel faster (e.g. roads), but also things that serve as brake (e.g. slopes, waterbodies) or even barriers (e.g borders). When preparing the cost raster one also needs to consider which means of transportation are available to the people that we represent in the accessibility map. Usually it is assumed that the people use the fastest means of transportation. This means travelling by car or bus on the road and on foot when off-road.
Input layers used
• Land cover (obtained from WLRC) to define the travel speed off-road (e.g. less vegetated areas allow for a faster pace than densely vegetated areas)
• Roads/infrastructure (EthioGIS II) to define the travel speed using public transport depending on the road/infrastructure type
• Slope (ASTERDEM) to reduce the travel speed with increasing slope
• Rivers and water bodies (EthioGIS II) to reduce the travel speed when no bridge / ferry is available (rivers and water bodies are not considered as transportation routes) |
| accessInformation:
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All layer from www.wlrc-eth.org, Models: Kaspar Hurni, Elias Hodel, CDE, University of Bern www.cde.unibe.ch |
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50000 |
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[] |
| description:
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<DIV STYLE="text-align:Left;"><DIV><DIV><P><SPAN STYLE="font-weight:bold;">etnatrvltimeadab</SPAN><SPAN STYLE="font-weight:bold;">webm</SPAN><SPAN STYLE="font-weight:bold;">.tif</SPAN></P><P><SPAN STYLE="font-weight:bold;">etna</SPAN><SPAN>: National </SPAN><SPAN>D</SPAN><SPAN>ataset Ethiopia</SPAN></P><P><SPAN STYLE="font-weight:bold;">trvl: </SPAN><SPAN>travel</SPAN></P><P><SPAN STYLE="font-weight:bold;">time: </SPAN><SPAN>time</SPAN></P><P><SPAN STYLE="font-weight:bold;">adap: </SPAN><SPAN>Addis Abeba</SPAN></P><P><SPAN STYLE="font-weight:bold;">webm: </SPAN><SPAN>WebMercator projection</SPAN></P></DIV></DIV></DIV> |
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| catalogPath:
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| title:
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etnatrvltimeadabwebm.tif |
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| tags:
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["Ethiopia","trafic","travel","emergency road condition","accessibility","surface"] |
| culture:
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de-CH |
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| minScale:
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20000000 |
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