What is a field boundary?

[m-mohr]

I think we should start a discussion about what a field boundary is - or there should be a type-like field for boundaries in core.

I just stumbled across a dataset (Thuringia, Germany) that included (in my view) more than just agricultural fields, e.g. forests.

To make sure that we don't mix things up, we should try to define something that guides a user.

[petescarth]

Good discussion. We're into mixed farming (Cibo Labs) and define a "field" as a management unit that's usually inside a "paddock", and the paddocks are mostly (given surveying errors and image errors) within a "cadastral boundary". This, I suspect, is a local definition.

Paddocks can be large—some in our system are ~90,000 ha, so close to the Fiboa spec max size—but they are relatively stable over time, whereas our field bounds can change multiple times/year.

This definition differs from what I commonly see elsewhere, where "field" and "cultivated area" distinguish the fenced/surveyed bounds from the management.

Either way, some way to distinguish these two boundaries with say, a type-like field is essential.

Other definitions use "fields" but include landUse and grazableArea to inform that there are ungrazable areas such as forests, dams etc.

Also, it's worth looking at Datalinker-Org for some thinking on this - they define a few farm data classes.

It would certainly be helpful to have a consistent definition for traceability and conformance that could fit into UN/CEFACT.

[StefanBrand]

Thank you, @m-mohr for pointing me to this discussion. I had added a viewpoint in #28 (comment) and here are responses to your questions:

Would it be meaningful to split the MultiPolygons that you get into single Polygons?

Not from the authority's perspective: These parcels are managed by the same farmer and have the same crop (mostly grassland). The farmers receive subsidies for the whole parcel, not for subparts.

From a satellite monitoring perspective it might make sense: The farmer might have their sheep on one side of the hedge in one week and on the other side of the hedge in the other week. Then we are talking about "partial grazing", and splitting the parcel up would result in more fine-grained monitoring results, i.e. subpolygon 1 was grazed during CW 19 and subpolygon 2 was grazed during CW 20.

Who assigns the IDs, i.e. is it possible to have unique IDs per Polygon after the split?

No, the IDs are assigned by the authority based on a farmer's subsidy application. From their perspective, the subparts of the multi-polygon still belong to one entity.

Do they regularly have different crops planted?

I'm mostly talking about grassland, which does not change across years.

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In response to the line on the main README of the specification:

The Field Boundaries for Agriculture (fiboa) project is focused on making field boundary data openly available in a unified format on a global scale.

Maybe my data exchange use-case with fields that are prepared for satellite monitoring (split by hedges, inner buffer) does not fit with the open data goal of fiboa. In this case I would argue that a field can only be a single polygon.

[m-mohr]

There could be potentially be interesting take aways in https://adaptstandard.org/docs and ADAPT/Standard#97

Also interesting: https://aggateway.org/Portals/1010/WebSite/About%20Us/FIELD%20BOUNDARY%20FLYER%20122123.pdf?ver=2024-01-03-212959-590 :

Field
A named and farmer-accepted physical space where production agriculture takes place used to partition and identify data.

Field Boundary
A geometry that identifies the geo-spatial coordinates of a field. The boundary can be used to define the area for a particular operation, a particular crop or crops, or for legal purposes. A field can have different boundaries that may vary in geometry based on their specific use but are always either a polygon or multi-polygon

[m-mohr]

We didn't really came to a conclusion today, e.g. what about forests, pastures, orchards, etc.
Could we potentially define at least a very high-level categorization that people can filter on if we don't restrict/define field boundaries?

Note from the meeting:

why was a field constructed? => ?
how was a field constructed? => determination_method
=> two different things
=> leads to accuracy for field boundaries (what can you use it for)

[ivorbosloper]

This is a discussion that keeps popping up. The only answer is: it varies. There is no strict global definition, we only have local definitions.

A farmer can, at a specific time, concurrently have many different "fields" on the same spot, with almost with the same geometry but for different purposes. He will refer to them as a "field" with the same name, but depending on the context it's different geometry/properties. I will illustrate with some local examples I'm aware of, a farmer has:

• Cadastral field, delineating ownership boundaries. In the open national cadastral dataset in NL, each field now has a "precision" (mostly depending on the period in time it was surveyed). They are 'indicative', if you want to use these boundaries in a legal process (e.g. neighbour dispute) a surveyor needs to locally measure it first. A farmer sometimes pays some lease/rent or taxes based on the (area of the) cadastral plot. Keep in mind that the cadastral plot can also contain non-cultivatable area like open water or buildings, so it's not the same as a crop field.
• Paddock. A large, continuous are of land that's stable for a longer period, mostly used or owned by one party. The farmer names for a "Paddock" vary regionally (dutch: hoek, kavel, perceel)
• Crop Field. A field in a farmers administration (e.g. Farm Management System) that is cultivated by a single crop. Variable is how to handle different varieties or planting/growth stages.
• Reference Parcel (Inspire definition). A geographically delimited area retaining a unique identification and area value eligible for aid payments. Basic spatial unit for the administration and geographical localization of agricultural parcels. May contain one or more declared agricultural parcels in IACS and may be cultivated by one or more farmers. This is EU-subsidy outer boundaries. Farmers are not supposed to declare subsidy crop fields outside of these areas, but reference parcels are not necessarily fields that are recognizable by a farmer. If there's no hard-break (roads, water, etc) between fields with different owners, they are 'dissolved' to a single large reference parcel. Quite some EU member states publish them as open data.
• Basic Payment Scheme (BPS) field. Subsidy-declared crop fields. Defined in 'Crop types' focussed at a local country and mixed with subsidy related goals. These are published as open data by many EU member states. You can see the result in all the different code lists collected by EuroCrops.
• Fertilizer regulation field. The BPS fields are subsidizable, but not always completely fertilizable (e.g. manure application, or articifial fertilizer, etc). So there's a different declaration process and different areas. May be influenced by distance to waterways, nature conervation areas,
• Nature conservation field. Specific areas where nature is conserved, for birds or plant species. Mostly meadows/grassland, e.g. agree to postponed mowing practices to allow field bird eggs to hatch. Partly overlap with crop fields.
• Controlled Traffic Farming field. If you work with computer steered machinery (autonomous or person-operated), you might need other field definitions. If your sprayer is 60 meter wide, and there's a high obstructing object (building, pole, electricity pylon), you might want to avoid certain paths/areas. Some precision farming used define their own field measurement method, see e.g. GAOS
• Irrigation field. Areas that are irigatable. Can be a part of a paddock/crop field (with irrigation cannons, drip irrigation, pivot rangers, or other methods installed). Some countries know large (pivot ranger) installations covering many fields.
• Contract fields. Some crop yields are sold on the market after harvest (e.g. grains). But other crops can be 'hedged' or contracted and advised before seeding/growing/planting by a buyer or food processor. These contracts can be agreed on 'area' or on specific 'contract fields'. Some Farm management systems or contractor portals require farmers to add information / observations on these contract field.

The list is probably longer. Think of soil sampling locations, or erosion areas requiring specific practices.