Learn to Validate

Validation is an important part of the Missing Maps process. Getting a second, third, or fourth pair of eyes on mapped features goes a long way in ensuring the quality of data being added to OpenStreetMap and being used in vulnerable communities around the world. Validating requires confidence in your mapping abilities as well as the willingness to help coach and advise newer mappers. The Missing Maps Project is a community of mappers with different levels of mapping experience, all who have a common goal of improving the availability of quality data for humanitarian use.

1. Identify if becoming a validator is right for you.

Validating isn’t for everyone; validation requires patience and attention to detail. Some experience mapping in OpenStreetMap and HOT projects is a must, but don’t feel that you need to be an expert to start. If you’re new to Missing Maps or OpenStreetMap mapping in general, head over to our resources for new mappers. Check out our Validation FAQs to gain some insight on what validating entails.

2. Build your skills.

Becoming a more efficient mapper is crucial to becoming a validator. The JOSM Editor is a customizable editor for OpenStreetMap with a number of tools and plugins to make mapping and validating easier! Check out this guide to validation using the JOSM editor. For instruction setting up JOSM, you can also head over to LearnOSM .

While validating in JOSM is preferred, you can also begin to improve the map through iD editor. Check out this video to learn some of the things to look for:

3. Collaborate as part of the broader community.

Different validators have different techniques for validating. Join the conversation on the HOTOSM Slack validation channel or reach out on the HOT Mailing List . Contribute resources that you find helpful and give back to the community! Being a part of the Missing Maps community means working together in a positive and inclusive environment; when giving feedback to mappers, be sure to keep a positive tone and stay mindful of their contributions and desire to help - it’s what keeps OSM growing!

4. Validation FAQs

How do I know when I’m ready to validate?

After you’ve had some experience mapping, you may find yourself correcting other contributors work. When you find that you are doing this on a regular basis, and you are finding it easier to spot and correct the mistakes, Validating is not to every person's liking but reach out to the HOTOSM community and ask for guidance! We’re happy to help!

Can I validate with iD Editor?

Yes you can but it is a lot more difficult to catch all the errors. JOSM Editor has a lot more tools that help new validators find the errors and also to fix some of them so it is preferable that you learn to map with JOSM first.

How do I get started validating?

The first thing you need to do is learn about what validating is. The Validtating Data wiki is a great place to start. You’ll want to learn to edit using the JOSM Editor. JOSM has a number of very useful validation tools which can make the process much easier and more efficient.

What are the steps when validating a project?

The first thing to do is carefully read the instructions for the project you are going to validate so that you understand what the mappers are being asked to do. When checking out each task, do a quick once over to size up the quality of the mapping. Change or modify what is not in-line with the provided instructions, and depending on the amount of time you have available, either complete the task to how it should be mapped or invalidate and leave a constructive comment on why you are invalidating.

How do I know the task is mapped well enough?

Before you start validating check out the instructions tab on the project. See what the requesting organization is looking for (buildings, buildings and roads, roads, landuse, etc). When you check out a task make sure that everything being requested is mapped. If looking at buildings make sure they are all squared (corners right angles) or circled, depending on the shape. Do this on a building by building basis as not every building will need squared edges. Make sure every feature is tagged, not just area=yes.

How should I be tagging roads?

Typically, most HOTOSM tasks will request that you follow the Highway Tag Africa Wiki. This is due to “the road conditions in African countries not always corresponding to their economic and social role. A road typology should be based on the road importance and not on the surface or the visual appearance of a road.

Should I just review the task and invalidate or should I finish the task and validate?

This ultimately depends on how much time you have to validate. If you open the task and it’s obvious that the instructions weren’t followed and there are a lot of features that remain unmapped, then invalidate. If the task is complete but just needs some cleaning up (i.e. squared buildings, adding one or two more buildings) then it is advised that you fix what needs to be fixed in the task, and leave a detailed comment for the user who marked it as done including ways that this task could have been mapped better.

What sort of feedback should I give?

Timely, positive, and constructive. Many projects are mapped by beginners at mapathons. Please remember that we were all new mappers at one point, and consider how your tone could impact the decision of a mapper to return to map again. If you find a number of tasks that have been completed by the same mapper, you only need to tag them in the comment once or twice. If the contribution by the mapper is over 2 weeks old, it is not necessary to tag the user.

When leaving a comment, please tag the mapper in the comment using the “@” key. See some examples of useful comments below:

  • Well-mapped task (Validated): Hi @user, thanks for contributing! Everything here looks great!
  • When a very new mapper is good, let them know! Good work @user. You are correctly identifying the buildings/roads from the background imagery and mapping them at the correct size and shape. Thank you for your time (or Thank you for contributing to this Project). Please keep mapping!
  • Okay-mapped task (Validated): Hi @user, thanks for contributing! I found a few additional buildings/roads that could be mapped here, so I went ahead and mapped them. Also, please be sure to square your buildings, which can be done by pressing `S` in iD editor or `Q` in JOSM. I finished everything up here. Thanks again!
  • Poorly-mapped task (Invalidated): Hi @user, thanks for contributing! It looks like there are quite a few buildings left to map here. Make sure if the task isn’t complete, to click `finished mapping` instead of `done`. If you have questions about what should be mapped, check out the instructions tab. Please reach out if you have any questions!