Project Type - Find Features

A 6 squares layout is used for this project type. By tapping you can classify a tile of satellite imagery as yes, maybe or bad_imagery. Project managers can define which objects to look for, e.g. “buildings”. Furthermore, they can specify the tile server of the background satellite imagery, e.g. “bing” or a custom tile server.

Find Features projects have projectType = 1.

Project

To create a Find Features project, you need to add all information and upload a bounding polygon as well as fill in some information about your project.

In addition to the common project fields documented in the data model, Find Features projects carry the following project-type-specific fields:

Parameter	Type	Description
zoomLevel	int	Web Mercator zoom level at which tiles are served.
tileServer	object	Raster tile server configuration — includes a server name, url, credits, and an optional apiKey.

Group

The grouping algorithm uses the extent of a project as an input and generates chunks of tasks lying next to each other. Each group has a height of three tasks and a width of approximately 40 tasks.

In addition to the common group fields, Find Features groups carry tile-map-service bounding-box coordinates:

Parameter	Type	Description
xMax	int	Maximum tile-X coordinate covered by the group.
xMin	int	Minimum tile-X coordinate covered by the group.
yMax	int	Maximum tile-Y coordinate covered by the group.
yMin	int	Minimum tile-Y coordinate covered by the group.

Task

Tasks are saved for tutorials, since their spatial information can be derived from the spatial extent of the corresponding group. Here, the tutorials are saved based on the project that it is derived from.

Parameter	Type	Description
taskX	int	The x coordinate characterises the longitudinal position of the tile in the overall tile map system taken the zoom level into account. The x coordinates increase from west to east starting at a longitude of -180 degrees.
taskY	int	The y coordinate characterises the latitudinal position of the tile in the overall tile map system taken the zoom level into account. The latitude is clipped to range from circa -85 to 85 degrees. The y coordinates increase from north to south starting at a latitude of around 85 degrees.
geometry	string	Each task has a polygon geometry, which can be generated by its x, y and z coordinates. At the equator the task geometry is a square with an edge length of around 150 metres covering circa 0.0225 square kilometres. Due to the web Mercator projector the task geometry will be clinched with increasing distance to the equator. At the same time the area per task will decrease.
url	string	The tile URL points to the specific tile image described by the x, y, and z coordinates. Usually, the image has a resolution of 256 x 256 pixels. However, some providers also generate image tiles with higher resolution (e.g. 512 x 512 pixels).

Result

Results follow the common result shape, with results: dict[str, int] keyed by taskId. The integer encoding for Find Features is:

Value	Meaning
1	Yes
2	Maybe
3	Bad Imagery

Whenever users indicate “No building” by just swiping to the next set of tasks, no data entry is created. “No Building” classifications can only be modelled retrospectively for groups where a user also submitted at least one “Yes”, “Maybe” or “Bad Imagery” classification.