Documentatie/Create-b-cropfield.md

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## Creating a cropfield
This page explains what a cropfield is, and how to create one through the API.
Agricultural datasets generally refer to a specif crop, at a specific location at a specific time.
Therefore, we need to create a "Cropfield" item, to define this location and a timeframe our data relates to.
A cropfield provides a convienient way to group all data for a crop grown on a specific plot during a season.
Farmmaps also uses the cropfield to collect and prepare context data such as weather, satelite imagery etc.
To create a cropfield we:
* Get the parent folder to place the cropfield under
* Create the cropfield
**Prerequisites**
To create a cropfield we need:
* an acces token
* coordinates of the cropfield (what points define the plot contour)
* a startdate and an end date (what timeframe does this data aply to)
### Get parent element
First, we'll get the parent code needed to place the cropfield in the hierarchy.
Usually this is a cropping scheme.
So when the code of the crop field is known, use this code as parent code to create the crop field and go to the next chapter.
## Get cropping scheme
When the cropping scheme code is not known, we need to start from the top of the hierarchy, which is my_roots.
**Request**
Replace `<acces token>` with your actual token.
```http
GET https://farmmaps.eu/api/v1/folders/my_roots HTTP/1.1
Host: farmmaps.eu
Accept: application/json
Authorization: Bearer <access token>
```
**Response**
The response will be something similar to:
```http
HTTP/1.1 200 OK
Date: Fri, 27 Aug 2021 19:00:55 GMT
Content-Type: application/json; charset=utf-8
Connection: keep-alive
Server: Kestrel
Cache-Control: no-store,no-cache
Pragma: no-cache
Content-Length: 835
```
In the list returned, search for item which ends with USER_IN, which is shown above.
This item will be the parent of the cropping scheme.
So make another call to check if a cropping scheme exist.
**Request**
Replace `<acces token>` with your actual token.
```http
GET https://farmmaps.eu/api/v1/items/f25d8765a1cd407cb235961c73c268cf:USER_IN/children HTTP/1.1
Host: farmmaps.eu
Accept: application/json
Authorization: Bearer <access token>
```
**Response**
The response will be something similar to:
```http
HTTP/1.1 200 OK
Date: Fri, 27 Aug 2021 19:17:36 GMT
Content-Type: application/json; charset=utf-8
Connection: keep-alive
Server: Kestrel
Cache-Control: no-store,no-cache
Pragma: no-cache
Content-Length: 1519
```
When the list is empty, you need to create a new cropping scheme, which is described in another thread.
The `parentcode` we need for creating a crop field is **"f3ee8e3ac55b43bc89757bcaedc89992"**
### Create the cropfield
Now we can create the cropfield. We do so by setting `"itemType": "vnd.farmmaps.itemtype.cropfield"` and adding data to the geometry parameter.
Generally, a cropfield contour would be defined as a polygon, so we add `"type":"Polygon" and all the coordinates.
We also need to specify a `dataDate` and a `dataEndDate` to indicate the the timeframe of the growing season.
The `dataDate` needs to be before `dataEndDate` and cannot be on the same day.
**Request**
```http
POST /api/v1/items HTTP/1.1
Accept: application/json
Authorization: Bearer <acces token>
Content-Type: application/json
Cache-Control: no-cache
Host: farmmaps.awacc.nl
Accept-Encoding: gzip, deflate, br
Connection: keep-alive
Content-Length: 916
```
**Response**
```http
HTTP/1.1 201 Created
Server: nginx/1.14.0 (Ubuntu)
Date: Fri, 27 Aug 2021 19:21:36 GMT
Content-Type: application/json; charset=utf-8
Transfer-Encoding: chunked
Connection: keep-alive
Cache-Control: no-store,no-cache
Pragma: no-cache
Content-Encoding: br
Location: /api/v1/items/8ecbaa2d85d5484db7f16b281b7cd013
Vary: Accept-Encoding
```
**Troubleshooting**
|Status code|Description|
|---|---|
|201|Cropfield created successfully|
|401|Error: not authenticated|
|403|Error: No write permissions in parent item|
|404|Error: Parent item not found|
Now that the cropfield has been created, we can start the processing by running a task.
This will collext all context data for the cropfield.
We need the ItemCode of the cropfield to start the task so keep this at hand.