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Edge-matched COD-AB-EM layers (administrative level 0 shown) and UN Geo Hub 1:1m boundary (orange)
Edge-matched COD-AB (COD-AB-EM) user stories
I am an Doctors without borders provider and need to prioritize where to go. This site says there are four doctors deployed to location A and three doctors deployed to location B. I am an obstetrician, does location B automatically need my attention first? | ||||
Edge-matched COD-AB (COD-AB-EM) questions and answers
What are COD-AB-EMs?
COD-AB-Ems are copies of the original definitive COD-AB that have had their external feature polygons extended or shrunk to fit the United Nations Geo Hub 1:1m boundary. They therefore fit the COD-AB-EM of neighbouring countries, when available. They may be suitable for cartographic visualizations and might also be useful for topological analysis of lower administrative level international connectivity.
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How can I find which countries have COD-AB-Ems?
The matrix in the “COD-AB features” page of the COD Portal [SOON TO COME] has a ‘COD-AB-EM’ column that indicates which countries have COD-AB-Ems. COD-AB-EMs are prepared for some of the countries with ITOS geoservices as indicated in the ‘Geoservices’ column in the main page matrix. No countries lacking Geoservices have COD-AB-EMs.
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How are the COD-AB-EMs created?
ITOS merges two line layers, one made from the lowest COD administrative level polygons and the other made from the United Nations Geo Hub 1:1m boundary polygons. COD lines are clipped when overlapping the UN boundary and extended when needed. Care is used in this step to not simply extend the line straight forward to the boundary but to determine where the border would logically continue.
A polygon layer is created from the lines after cleaning their topology errors. Single-part points created from exploded multipart polygons in the COD are then spatially joined to the polygons for attribution. All multipart polygons are dissolved to match the number of admin features in the COD-AB. This layer is then dissolved to create the higher administrative boundary layers.
Are edge-matched COD-ABs authoritative?
Yes, for all attribute (name and P-code) information. COD-AB-EMs and the definitive COD-ABs have the same feature sets. However, the geometry of outer polygons may have been compromised.
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