Here’s the issue:

Africa map

How closely your field boundaries align with our field boundaries

How close the number of fields you map is to the number that we map

So the process and scoring is fairly simple. However, interpreting what is and isn’t a field can take some practice, and we are also only interested in certain types of fields.

To learn more about these skills and exactly what type of fields we are after, please read the mapping rules we have provided.

humans icon help us icon web icon Yellow icon attention icon check mark icon Yellow icon align icon check icon eye icon
Mapping outside field example
files icon draw icon eye icon repeat icon



submit icon cash icon target icon cash icon check icon question mark icon assesment icon alignment icon

Your quality score

We assess your work's quality according to two components:

Well, every once in a while we sneak in a HIT we have already mapped, which allows us to measure how well your map aligns with ours.

 How do we determine your quality score ?

We will pay you for each HIT, assuming that your quality score receives at least 60 out of 100 possible points.

Submit the HIT. Start another one

Repeat this procedure for all fields within the box.

If the field falls partly outside of the box, please also map the part that is outside.

If there are any, mark each field  by drawing a polygon along its boundaries.

Fields often have traces of parallel lines (because of ploughing) inside their boundaries.

Fields usually have a semi-regular shape that is distinct from their surroundings,

Identify crop fields falling totally or partially

within the white box in the center of the satellite image.


Choose to view and accept HITs from the requester “Mapping Africa”.

search for HITs

containing the words "Mapping Africa"

The process works like this:

You are ready to start mapping

log on to Mechanical Turk

Once your account

has been registered by Amazon,

and register for an account.’s Mechanical Turk service

To help us, please visit

In order for our project to be a success,

we need you.

Although there are computer algorithms to map these fields, they aren’t as good

as the human eye.

This is where you come in.


We are trying to map African farmland using the power of the Internet.

As a result, we have launched this mapping initiative to get a better idea of where and how much farmland there is in Africa.

Due to the wide range of error and the unreliability of the data, it can be difficult to understand key issues such as food security, or to predict where agricultural expansion will happen.

They are prone to overestimating and underestimating farmland in various locations.

The best data that we have so far are not incredibly accurate.

Of particular note is Africa, which is predicted to experience an explosion in agriculture in the coming decades.

We have a pretty good idea of farmland distribution in Europe and North America, but we have a lot to learn about other parts of the world.

our understanding of where people

are farming is limited.


Status update

November 4, 2014

Our goal is to work with Internet users like you to accurately map African farmland.

African farmer



Mapping Africa was developed at Princeton University with support from IIASA, NASA and NSF

Lyndon Estes

Lyndon Estes

Associate Research Scholar, Woodrow Wilson School

Dennis McRitchie

Research Computing Senior Software and Programming Analyst,

Academic Services, Office of Information Technology.

Dennis McRitchie
Kelly Caylor

Kelly Caylor

Associate Professor of Civil and Environmental Engineering.

William Guthe

Research Computing Geographic Information Systems Analyst,

Academic Services, Office of Information Technology.

Lecturer in Public Affairs, Woodrow Wilson School.

William Guthe

"We are always looking for collaborators, particularly in Africa, to help us achieve our goal. We particularly need:

- GPS collect field boundary data (to help with accuracy assessment)

- People to get out the word

- Ideas

If your interested please email us at:


Stephanie Debats

Stephanie Debats

PhD Candidate, Civil and Environmental Engineering

Jonathan Choi

Undergraduate student, Class of 2015

Jonathan Choi
Réka Zempléni

Réka Zempléni

Undergraduate student, Class of 2016

Gabrielle Ragazzo

Undergraduate student, Class of 2015

Gabrielle Ragazzo