Saraya, Senegal

OpenStreetMap Data for Malaria Prevention



Saraya Tracing

Malaria is endemic throughout Senegal. As part of the ProAct malaria case management system, the Peace Corps Stomp Out Malaria program in Senegal is requesting assistance building a better base map of villages in the Saraya district of southern Senegal. In collaboration with the Senegalese Ministry of Health, Peace Corps and Senegalese public health professionals will conduct a study to determine the importance of geographic proximity in malaria transmission. In other words, the team seeks to determine whether all members of a household should be preemptively treated for malaria if one member tests positive. The purpose of these tasks is to trace missing buildings and roads.

Getting Started


OSM License

In order to coordinate the various mappers collaboratting on this task the OpenStreetMap Tasking Manager (OSMTM) is going to need to access your OSM account. If you havent logged in when you select a grid square to edit it OSMTM will ask permision at that time. Once logged OSMTM will ask you which editor you prefer to use. For first time editors iD may be the easiest. If imagery has been provided for the grid square you have selected than you may be required to agree to the terms of a license to make use of the imagery. If a license agreement appears at this stage please review it before signing.

https://cloud.githubusercontent.com/assets/7431774/6679362/fa6672c6-cc1c-11e4-85a4-d51e5da60523.gif

Imagery

Make sure you’re using the right background imagery. For this task, you will have multiple types of imagery to choose from but you should use the default custom imagery whenever possible. If and only if the screen is black, try switching to Bing imagery. This option can be found on the navigation bar on the right of the screen.

https://camo.githubusercontent.com/056ceb6a29e1b26db4bab53326886d71ff70df30/68747470733a2f2f636c6f75642e67697468756275736572636f6e74656e742e636f6d2f6173736574732f393635373937312f363336303133302f62643363303838652d626334352d313165342d396565342d3431343130376530373739622e676966

OSM iD Editor Settings Brightness Adjustment

Often the default brightness settings in iD editor makes the background imagery difficult to see, but increasing the brightness will help. You can do this in the “Background settings” tab (Shortcut: b).

https://cloud.githubusercontent.com/assets/2665840/6714557/439cd518-cd6f-11e4-81ae-82540f486d52.gif

iD vector alignment

While editing you may encounter a situation where existing features exist that were drawn based on older low-resolution imagery. You need to adjust the existing vectors in iD editor to match the new imagery.

https://cloud.githubusercontent.com/assets/2665840/6720917/5ae54f82-cd9e-11e4-955f-16de6bf61ec7.gif

Splitting A Square

Having selected your square and inspected it with the imagery in place, you may realise that there is far too much detail for one person to map. In this case you may want to split your square into smaller more reasonable tasks. As a general rule if you think that it will take longer than 2 hours to map all the tasks features in one square than you should probably split it up.

It is important to use caution when splitting squares because it comes at a cost - any usefull comments previously completed in the square will be lost.

To split your sqare simply click split the button in Tasking Manager

https://cloud.githubusercontent.com/assets/7431774/6856929/9b961d18-d3d9-11e4-8bd6-b31e8f59cd12.gif

Buildings


Metal Roof Buildings

Many buildings in the Saraya District of Senegal are made with mud and brick and have a metal roof. Please label these as general buildings. Community-based team members will update the labels.

https://cloud.githubusercontent.com/assets/11095450/10434907/761213ae-70ea-11e5-9798-f8c1247d568e.png
https://cloud.githubusercontent.com/assets/11095450/10435346/6770ed5e-70ed-11e5-9922-eebebf6da9ca.jpg
https://cloud.githubusercontent.com/assets/11095450/10434922/a8b40e5c-70ea-11e5-95d2-f18625192003.png

Thatched Roof Buildings

Many buildings in the Saraya District of Senegal are made with mud and have thatched roofs. Please label these as general buildings. Community-based team members will update the labels.

Thatched roof buildings are typically round in shape. Use the letter “o” button on your keyboard after tracing to make your polygon a perfect circle.

https://cloud.githubusercontent.com/assets/11095450/10435144/27459802-70ec-11e5-9a2d-2dcfabb3f673.png
https://cloud.githubusercontent.com/assets/11095450/10435146/2a873750-70ec-11e5-849f-2f26c8888a19.png
https://cloud.githubusercontent.com/assets/11095450/10435387/b889d07a-70ed-11e5-8b15-9abf8817dfdc.jpg

Roads


Residential Roads

The majority of roads that you see in the imagery should be classified as “residential”. As the name implies, these roads connect houses and run through neighborhoods. These roads are easily seen but won’t look particularly wide - most of them are only about one lane wide. When in doubt, classify a road as residential.

https://cloud.githubusercontent.com/assets/11095450/10436021/cb22f85c-70f1-11e5-9c0a-80ee576f8810.png
https://cloud.githubusercontent.com/assets/11095450/10435505/715aa5de-70ee-11e5-8635-8bb6d59926a9.jpg
https://cloud.githubusercontent.com/assets/11095450/10436023/cede0374-70f1-11e5-8f87-4a017969b703.png

Unclassified Roads

Tertiary roads connect towns and villages and are typically the major road passing through a village in the Saraya District. Unclassified roads also tend to be wider and more obvious from the satellite imagery than residential roads.

https://cloud.githubusercontent.com/assets/11095450/10435841/8e3daf50-70f0-11e5-97f8-e24821c5c2ce.png
https://cloud.githubusercontent.com/assets/11095450/10435903/f1f19fb6-70f0-11e5-8f11-8577b8d4c6e1.png
https://cloud.githubusercontent.com/assets/11095450/10435561/c26d723a-70ee-11e5-85fe-24d6487b49db.jpg

Track

Tracks are smaller roads mainly used for connecting villages or towns to agricultural and or forestry sites. A track will typically only fit a motorcyle, bicycle or pedestrians. For the purposes of this project, tracks are not a major priority to map but can be traced.

https://cloud.githubusercontent.com/assets/11095450/10436202/f5f10406-70f2-11e5-91e6-582a41f6dadd.png
https://cloud.githubusercontent.com/assets/11095450/10466058/1eff7f80-71c0-11e5-8a67-cbda3a788404.jpg
https://cloud.githubusercontent.com/assets/11095450/10436238/2ea7fdcc-70f3-11e5-8228-00556b420fd3.png

Roads Must Intersect

Roads must be connected where they intersect. Make sure the roads connect to each other where they cross. You should see a node appear at each intersection.

https://cloud.githubusercontent.com/assets/7431774/6626271/cefa345a-c8cb-11e4-8704-00197078a9e2.png

Validation


Validating Grids

OSM is constantly changing and no matter how filled out an area on the map is it is never done. The impression that validating a grid will mean that it will never be revisited leads many to feel intimidated by it. Anyone can validate! Just remember, do not validate your own work.

Validating a grid means that everything that needs to be done to meet the goals of the task you are working on. If the task is to map every type of feature possible and provide attributes this may be very complex and may require field verification but if the goal is to map basic features in a sparsly populated area this process is fairly straight forward.

https://cloud.githubusercontent.com/assets/7431774/6838233/436de6dc-d32c-11e4-8498-98ad7e6887fc.gif

Buildings

Now check if buildings are missing. If there are a large number missing, the grid can be invalidated. If it's only a few then it's simpler to add them as you check around.

Are the buildings correctly traced? Sometimes mappers do not trace buildings accurately & if you spot significant inaccuracies this needs correcting. You may find that a group of buildings looks like they match the shape of roofs but are displaced from where the building is in the imagery, this often happens when OSM has been traced based on imagery that has been misaligned. For the purposes of this task - unless the alignment is aggregious - leave the buildings if you suspect displacement is due to an imagery issue.


Highways

  • Highway tags are correct? Some mappers tag every highway as a track because they are not paved, but this is not a meaningful criteria in some developing countries considering the amount of unpaved roads. Check the wiki definitions, perhaps the Highway_Tag_Africa is relevant & you should research there before going any further. Road geometry.
  • Road Geometry Some mappers do not put enough details and others too much (eg a node every 10 or 20 m even if the road is straight). Delete extra nodes if they actually make a straight road weave.