During validation on HOT’s Tasking Manager giving feedback to mappers is crucial to enable improvement and encourage them to continue mapping. Beginners make the most errors, catching them as early as possible to provide constructive feedback can limit the quantity of errors and steer them in the right direction. This can lead to an overall increase in data quality.

I’ve outlined some of the most frequent feedback that I give to mappers while validating projects that involve mapping buildings as well as explaining the importance of intervening. Please feel free to use these comments in your own validation efforts on HOT’s Tasking Manager.

Issue	Feedback Comment	Importance
Unsquared buildings	Well mapped but please square your buildings after tagging them by pressing ‘q’ on your keyboard. Keep up the mapping - many thanks!	When we are ‘free-hand’ drawing buildings it is impossible to avoid creating corners that are irregular (not right angled). In reality most buildings do have right angled corners and we need our mapping to reflect that. Accurate building footprints are important because building sizes are often used to estimate population sizes for an area to conduct humanitarian activities.
Drawing several buildings as one building.	Thanks for mapping. Next time, you can improve by avoiding mapping several buildings as one building. Every building must be traced separately. Zoom in as close as possible to see the outline of the buildings, hit each corner of the building carefully. Look for shadows, open ground, changes in roof color and vegetation to differentiate buildings.	The humanitarian teams use the size of the buildings to estimate the number of people living there. This helps them to work out the approximate total population in the area and how much equipment or medication to bring with them. Buildings that are too big do not fit in with these calculations and lead to inaccuracies in the population count.
Overlapping buildings and highways	To ensure buildings/highways do not cross or connect, zoom right in and carefully place the building corners. If a road overlaps a building you should feel free to adjust the position of the road before mapping the building, thank you for mapping.	Road data is used in sat navs by humanitarian workers. A sat nav will think there is a dead end if it enters a building. This could add hours to a journey.
Using a different imagery instead of the imagery as instructed	Good work, thank you for mapping. The project instructions encourage switching different imagery so as to catch all the buildings in this location. In this project , you can also switch to Bing imagery as well. It has a lot of unmapped buildings.	This avoids missing out many buildings and other features since in most cases project managers select the most updated imageries.
Duplicate mapping	Thanks for mapping. You might need to zoom right in to clearly see if there are existing buildings that have already been mapped before you start adding buildings. Task squares on the Tasking Manager will automatically unlock after 2 hours, which opens them up for other mappers to work on. If you are continuing to map after two hours, then lock the square a second time, to avoid double drawing of features by different people.	It is important to have all the buildings mapped to enable appropriate allocation of resources during a crisis.
Building sharing nodes	Great work, thank you for your mapping! To improve for next time, please zoom in close enough when tracing to avoid buildings sharing nodes or else overlapping.	If buildings need to be adjusted or improved later on, it is much harder to do that if they share nodes with nearby features.
Wrong Tag Eg. Building Tagged as Landuse = residential, Area= yes	Thanks for your mapping! I noticed you tagged a few buildings as residential areas. Next time, remember all Buildings should be tagged as “Building”. When using satellite imagery to map it is best to assume that all the buildings we see are generic buildings rather than attempting to define their specific purpose - this is done later on by field mappers.	It is important for the local mappers/ field mappers to know what they are approaching, wrongly tagged features can misguide them and also waste a lot of time.
Spaces, trees, rocks, cars and even elephants(!) mapped as buildings	Thank you for mapping! Please, zoom in and out in order to clearly see if an object is a building or not. Look for a color difference between the roof and ground, shadows and regular geometric shapes (e.g. rectangles or circles).You can also use different imagery to compare for clarity.	Local mappers / aid workers could waste a lot of time traveling to remote rocks or trees to find no buildings, so it is important to have correctly mapped objects to avoid misguidance.
Untagged features	Thanks for your help! Please make sure to identify the objects that you are mapping. Several of them are untagged. Make sure to select the tag from the left hand side of your editor after you trace the object.	It is important for the local mappers to know what they are approaching. An untagged rectangle could be anything (field? forest?). If local mappers were looking to add information about buildings they could waste a lot of time traveling to unidentified rectangular objects.
Unmapped task, marked as “DONE”	Thank you for your mapping, this task was marked as done, however it had several buildings which still needed to be mapped. Next time please check your task very carefully before submitting it as complete, ensuring to map all the buildings. You can choose to unlock the task for someone else to continue mapping by selecting NO before submitting the task.	It is important to have all the buildings mapped to enable appropriate allocation of resources during a crisis or to plan humanitarian activities effectively.
Other features mapped in project when not asked to	Well mapped but remember that we are only mapping buildings in this project. This is detailed in the project instructions. Keep up the good work!	Humanitarian organizations set the features to be mapped based on their priorities - any time spent mapping other features might slow down the completion of their projects.

Live Validation:

Live Validation involves real time data cleaning conducted during a mapathon. It aims to give feedback to mappers as soon as possible after they mark a task in the Tasking Manager as mapped.

How Live Validation is done:

1.A validator joins a mapathon (either remote or in-person) accompanying the mapathon trainer. Ideally the validator gets a chance to introduce themselves near the start of the session and explain their role.

2.Once mapping has started, the validator uses Tasking Manager to focus on most recently mapped tasks: Within a project in the Tasking Manager under the ‘Tasks’ section select tasks that are ready for validation and sort by ‘most recent’. Carry out validation using JOSM and give feedback in the Tasking Manager.

3.After main training elements are covered - validator gives verbal feedback while screen sharing during the mapathon. It tends to be more polite not to mention mapper names - participants typically recognize the task they have been working on when you share your screen.

Advantages:

1.Capture data quality issues very early to prevent further occurrences by giving mapper feedback to improve.

2.Live validation helps the trainer to identify recurring issues where the mappers might need more guidance during the mapathon. The trainer can then adapt quickly and focus their training on those issues.

3.Live validation gives the validator the chance to give verbal feedback while also sharing those issues visually on their screen - this is an impactful way to give feedback, particularly compared to the typical method which only involves text-based feedback.

4.A validator gets the chance to demonstrate feedback channels (Tasking Manager notifications) with mappers to make them aware of where they can find feedback after a mapathon - this improves communication between the mappers and validators.

5.It visually demonstrates what validation is - it can sometimes be a difficult concept for new mappers to gain an understanding of. It gives mappers confidence that their mapping is being checked and this can encourage them to continue mapping.

6.When things go very wrong it demonstrates how much work is needed by a validator to clean things up. This may encourage a greater focus on accuracy by participants. Thereby it may improve data quality and make validation easier and faster.

Task selection

Humanitarian OpenStreetMap Team’s Data Quality Internship 2021 was a twelve week programme. An opportunity to become deeply involved within the Humanitarian OpenStreetMap Team and community while gaining readily transferable geospatial skills.

The interns focused on validating priority disaster response projects, projects with imminent field mapping and also on tackling the backlog of un-validated HOT projects. In total, they validated 74 projects across 12 countries, See here

The interns were led through a series of webinars hosted by a range of professionals in the humanitarian mapping sector. Meta, Kontur, Mapbox and OSGeo ran skill sharing sessions for the interns - this involved training the interns how to use tools which the organizations had created, for example Disaster Ninja, OSGeo Live and RapiD. This broadened the interns knowledge of geospatial tools and enhanced their ability to validate.

In addition several key individuals in the geospatial sector participated in Ask Me Anything sessions, where the interns heard about their inspiring geospatial career paths and had the chance to ask insightful questions

Interns also received live training in a wide range of geospatial tools culminating in their ability to confidently validate the work of other mappers.

Some of the training sessions were recorded, please view this playlist to see all of these in order. Of particular interest might be:

• If you’ve never used QGIS before but are keen to learn, here is how to setup and use QGIS to create maps from scratch in this two part series Episode 1, Episode 2
• If you’re already into validation but want to learn about the mysterious art of “3rd pass validation” check this video.

Highlights

Group photo of the interns