Hi, Sorry for coming back to you late. Finally, the ICRC Water and Habitat Specialist will not use the "ponds" data, so we can avoid to map it. I wish they come directly to discuss with the community on the list in the future.
Sincerely, Severin On Mon, Mar 10, 2014 at 6:03 PM, Tom Taylor <[email protected]>wrote: > On 10/03/2014 1:32 AM, David Litke wrote: > >> Hello, >> I am fairly new to mapping towns in Africa, but would like to help out >> on this project, especially since it is a water-related project and I am >> a hydrologist. I have a few comments/questions: >> > > As a new mapper relatively unfamiliar with Africa, I cannot stress the >> importance of any on-the-ground information that can be made available >> about how to interpret imagery. Otherwise, how can I guess what I am >> looking at? For example, in the Bassikounou imagery, what are these >> strange (sometimes very large) white spots (sometimes in the shape of a >> bow-tie), for example at 15.8604986, -5.9610567? Some kind of tent? >> Buildings, walls and roads: I can understand the importance of a good >> base map to the ICRC so they can use it for on-the-ground surveys of >> water-development information. >> > > [PTT] That square has the look of an institution (health centre or > school). Anyway, I would surmise that is a fairly new permanent piece of > construction financed from abroad. > > Intermittent ponds: Since this is very dry country, it seems to me that >> we happen to have imagery taken after a fairly strong thunderstorm event >> (like the one seen at the nearby refugee camp in 2012 >> <http://intersos.org/en/bulletin/news/malian-refugee- >> camps-under-water-floods>), >> >> and the water we see is essentially puddles left over from this storm., >> which will be very temporary in duration. What we are mapping >> essentially are the low spots in the topography where the water >> collects. I do not believe this has any relation to where groundwater is >> located. If the ICRC is interested in topography, they might be better >> off using SRTM elevation data - this also could be processed to find >> possible dry river and stream channels. >> > > [PTT] In Mali, it was obvious where standing water persisted throughout > the year from the darkness of the vegetation relative to surroundings. I > mapped such areas because of their impact on roads (generally have to > bypass) and farming use. > > > Trees: Are these Acacia trees? Since it is quite time consuming to map >> these, is it proven that the tree density is indicative of water >> availability? >> > > [PTT] You can quickly map trees by creating one node, then copying the > node (click on it and select copy from the edit menu), then clicking on > each successive tree location and doing paste. My purpose in mapping trees > was just to provide landmarks for navigating through the town streets. > Sometimes away from town a cluster of trees will be a meaningful indication > of water (e.g., oasis). > > Wells: Although we are not mapping wells, I was very interested in the >> email thread about wells (in Mali). I am very surprised that wells can >> be located by looking at imagery. It seems that only a small fraction of >> wells could be discernable, mostly only those that have paths converging >> at the well, or by the animal tracks made by oxen pulling up the >> buckets. It is very interesting to learn about these animal track >> patterns though - the length of the animal tracks might be used as to >> estimate the (maximum) depth to water). >> Dave >> *From:* Severin Menard <mailto:[email protected]> >> *Sent:* Thursday, March 06, 2014 10:14 AM >> *To:* [email protected] <mailto:[email protected]> >> *Subject:* [HOT] Mapping Bassikounou, Mauritania - ICRC request >> >> Hi, >> ICRC requested us to map an AOI (Area Of Interest) around Bassikounou, a >> town close to the border with Mali, for a development project about >> drinkable water. The approach is the same than for Walikale in DRC. To >> know more: http://tasks.hotosm.org/job/447 >> As you can see, I added a banner to make clear what the job is from, for >> and about. For sure HTML and wording could be improved, please make >> suggestions. >> The map features are a bit more various than usual (eg intermittent >> ponds - please find a link provided by the local Watsan specialist tp >> have an idea how to identify them on Bing imagery - and trees). >> I also added a picture and a video of Bassikounou that I found in the >> web, to have a better idea of what look like the streets and the >> outskirts. >> Sincerely, >> Severin >> >> ------------------------------------------------------------------------ >> >> _______________________________________________ >> HOT mailing list >> [email protected] >> https://lists.openstreetmap.org/listinfo/hot >> >> >> ------------------------------------------------------------------------ >> <http://www.avast.com/> >> >> This email is free from viruses and malware because avast! Antivirus >> <http://www.avast.com/> protection is active. >> >> >> >> >> >> _______________________________________________ >> HOT mailing list >> [email protected] >> https://lists.openstreetmap.org/listinfo/hot >> >>
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