[HOT] HOTOSM #699: About identification of plantations (HOTOSM #699: About identification of plantations in Africa (as for cassava, manioc)

[S Volk]

Hi, Some more about Africa plantations:
Sometimes images shows cassava plantations like rounded light green patterns, planted in not very regular rows (new plants).Sometimes shows only brown rounded holes, but in the exact place where there were plants that were already picked.It only changes from sides to sides of same uncovered lands seasonally.Anyway mostly it will be planted again soon, so its allotments usually are permanent. So it keeps being the same farmland landcover.
Since it's planted in small strips or areas (once it's a kind of manual plantation by few individuals, usually not large areas managed by machines), they are sometimes isolated, sometimes following river margins or wetland.
Intending not to complicate too much, I think it will be more useful to map it contiguously when brown and green areas are together, since being the same seasonal plantation area (not in many disconnected strips, I did it before, but I think it's unnecessary perfectionism). Only when it's not disconnected by remarkable different features as portions of forest or rivers or non-used grassland, it may be mapped continuously). 
Paths can be found going though it by many ways. Plantation borders usually almost sure are ways for paths, if found straight paterns.
Also, I think it's better to tag cassava plantation as farmland (not orchard, since orchard is more propper for permanent plants, that are not removed in the harvest, like apple trees, pepper, etc). Cassava plant is entirely removed, since it is a tuberous root. In this area can be seen both green and brown areas of cassava planted and removed:
http://www.openstreetmap.org/edit?editor=id&#map=18/8.78502/-12.00690
In that area can be seen also a plantation of palms, recognized by its long leaves and some regular pattern, not being random. Most times I see it tagged as forest. Few times as orchard. So I followed tagging as forest (Wood only for natural groups). But now I guess, if to be more precise, it would be more proper for "orchard" when palms are found planted in regular patterns, since it's for picking its fruits (not mostly for cut it to use its wood, as landuse tag for forest). But guess it's not worth for changing all done around Africa. It makes no much remarkable difference for practice, and there are still much more unidentified features to be done.
Also about Sierra Leone plantations:https://en.wikipedia.org/wiki/Agriculture_in_Sierra_Leone
Regards, Sergio. Brazil.From: svolk2 at hotmail.com
To: hot at openstreetmap.org
Subject: HOTOSM #699: About identification of plantations (HOTOSM #699: About identification of plantations in Africa (as for cassava, manioc)
Date: Tue, 21 Oct 2014 17:55:47 +0300




Hi everybody, I'm contacing you to suggest an OSM wiki note about the identification of major plantations in Africa from sattelite imagery, for HOTOSM requests.
I realise this need, for example, for "cassava" plantation (manioc). It's one of Africa's major rural production, and it's everywhere in sattelite imageries we are mapping  (as in Sierra Leone's HOTOSM). 
But I found that many mappers, even experienced, don't know well how to identify it (nor softwares do it yet), mistaking it in landcovers as mud, wood, scrub, grassland, etc., or mapping alltogether with forests.
In the front page HOTOSM instruction note for https://wiki.openstreetmap.org/wiki/Highway_Tag_Africa, in the picture used there to show the type of Africa's "secondary highway tagging" (https://wiki.openstreetmap.org/wiki/File:Secondary-highway-sierra-leone-1.png) there is a remarkable cassava plantation, at the right side and in the bottom. This plantation is characterised by 1 to 1,5m rounded small plants in irregular rows, sometimes following river margins, even if dry, other times in isolated farm allotments. Its also important for mapping accesses to isolated small buildings, because it allows footpaths through it everywhere.
Wouldn't it be worth if you may put a note about cassava plantation (perhaps adding a note in the /Highway_Tag_Africa?Maybe in the same picture you use in Highway_Tag_Africa, since it's a good aerieal view of cassava, and it's the only link quoted people see in the front page instructions for HOTOSM #699? 
I think it would be very usefull for everybody, also for the others Africa's HOTOSM.
If you want, could take a look also at this aerial photo of cassava and its footnote (or others): [http://www.gettyimages.com/detail/photo/bangweulu-floodplain-zambia-aerial-view-of-high-res-stock-photography/72886297]
Thanks, sorry for bad english. Sergio 		 	   		   		 	   		  
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