My diary entries all all my own thoughts and do not represent OpenStreetMap, The Humanitarian OpenStreetMap Team (HOT) or any organisation using the HOT systems. Any errors are all my own work.

This first diary entry is based on my response to a mapper on the HOT Slack Channel asking about validation methods.

When it comes to HOT mapping and validation, I’d say there are not really any standards, or training to judge mapping against those standards. It’s a constant frustration of mine. However, the use of the data should be considered when validating tasks. If a road in Africa is a few meters out from a vehicle GPS while driving, does it really matter? The driver is going to follow the track. Relative positions are more important - do things match what might be seen in the field?

Skipping a task that you don’t feel experienced enough to validate seems a mature approach to me. I also try to map a few tasks in a project before validating tasks to get some understanding of the problems mappers may face.

I’ve only been seriously HOT mapping with some validation since early 2024, although I’ve mapped in a small way since April 2019, including my own locality. I’ve developed the thought that there are three basic types of validators;

1. Validators who simply approve or reject tasks. These validators are usually new validators and sometimes they are still new mappers! These validators may give basic feedback such as ‘more mapping needed’. This is not very useful. It is not targeted to the task problem or the mapper.
   I’ve seen projects requiring roads, buildings and waterways with validated tasks without rivers mapped where rivers are visible. This is task fixation on buildings and roads because this is the requirement of many projects. It shows that mappers and validators are not reading the instructions. Sadly, some instructions are very poor, but that’s a separate discussion!

2. Validators who reject tasks with feedback that is relevant to specific problems and named mappers, often with image based examples. I try to be one of these. I’m not just looking to get the project finished, but to develop the mapper skills. This is more beneficial to the long term mapping quality. I call this Validation for the Mapper. I’m trying to develop mapper skills to make future validation easier and hopefully complete projects more quickly.
   It is probably the most time consuming and frustrating type of validation as many comments are ignored as most mappers never review the history comments. Several cycles of new mapper submissions and rejections with no mapping changes may occur before a mapper does read the history and correctly maps the task.

3. Validators who used to be type 2 validators. but may have become frustrated with the cycles described in 2 and just fix all the problems themselves. The project makes more rapid progress, but the mappers have no idea if they mapped well or not. I call this Validation for the Project. It gets the project completed with good quality, but may take up unnecessary validator time and it does not improve mapping skills in others.
   This can result in more validation work over the long term for all types of validator because the mappers may think that what they have mapped was good enough when it was not.

I usually fix small problems such as two or three missed or misshapen buildings, but I will state what I did in feedback, sometimes with images. This is very time consuming. I won’t do lots of mapping as a validator as I value my time. I’d rather map well first time than have my time wasted fixing up large amounts of poor mapping. I reject such tasks with appropriate feedback.

The biggest issue with rejecting tasks is that most mappers only map once. The statistics are obvious. https://tasks.hotosm.org/ shows over half a million mappers, but the number of on-line mappers can be single figures. It is probably only over 30 when mapathons take place. Mapathons usually mean many of new mappers at once and the associated problems. However most of us have likely started with a mapathon, so they are useful events.

For validation training, I suggest you join one of the early in month Missing Maps London on-line mapathons. These are focused on training new mappers with the iD Editor or JOSM. There is usually some validation training depending on numbers and trainer availability.

The mid-month Missing Maps London on-line events focus on experienced mappers and potentially more challenging or restricted projects. These and other mapathons can also be found on the OpenStreetMap Calendar.

There are also recorded webinars and tutorials on the HOT YouTube channel to help mappers and validators. Some of the videos are short, some are very long! Additional webinars may be notified on the HOT Slack Channel from time to time. Some mappers and validators also respond to questions asked on the HOT Slack Channel and past conversation may be searched.

Hopefully we’ll see you on-line. Happy Mapping!