# How can you read a WKT in QGIS and use it as a layer of geographic information

## Learn how to read a Well Known Text (WKT) format in QGIS and use it as a layer of geographic information. Discover how the WKT format is used in QGIS and spatial databases, and explore the process of importing and exporting spatial data based on this standard

- How can you read a WKT in QGIS

In this article we are going to give some details about **what is the Well Known Text format ( WKT )** for the definition of geometries, its relationship with **Geographic Information Systems** and spatial databases.

We will also show how** **import and export** **spatial data based on this standard and **how to read a WKT in QGIS**, to use as layers of geographic information.

Contents

## What is the WKT format?

The **WKT or Well Known Text format** is a coding format specifically designed for characterizing and storing spatial geometric objects in vector format.

It is a very expanded format within the world of geotechnologies since it is a standard defined by the **OGC** and therefore it has been adopted by a large number of **Geographic Information Systems** and is accepted by other geospatial tools and libraries.

### Geometries supported in the WKT standard

Using **WKT** we can define different **types of geometries** how:

#### Basic geometry typologies:

- Points ( POINT )
- Lines ( LINESTRING )
- Polygons ( POLYGON )

#### Multiparty geometry typologies:

- Multipoints ( MULTIPOINT )
- Multilines ( MULTILINESTRING )
- Multipolygons ( MULTIPOLYGON )

#### Other types of geometries:

- Geometry collections: elements of different geometric typology.
- Three-dimensional points ( X, Y, Z )
- Four-dimensional points ( X, Y, Z, M )
- Polyhedral surfaces
- TIN ( Triangulated Irregular Network )

### Examples of definition of geometries in WKT

To propose some examples, we are going to show the appearance of some **geometries** “ translated ” into this format **WKT**.

The structure of a **WKT geometry** of type point is as follows:

1 | `POINT(10 20)` |

A three-dimensional point, meanwhile, would be made up of three coordinates. For example, to display a lift value on the Z axis:

1 | `POINT(10 5 3)` |

A multipoint would consist of:

1 | `MULTIPOINT((10 20), (30 50))` |

The geometry of a line in WKT format would have the following appearance:

1 | `LINESTRING (10 35, 5 15, 20 30)` |

A polygon would be defined as follows, so that the starting point and the end point are coincident :

1 | `POLYGON(10 10, 15 15, 10 30, 5 10, 10 10)` |

Finally, a multipoligone would be defined as follows:

1 2 3 4 | `MULTIPOLYGON(` `(10 10, 15 15, 10 30, 5 10, 10 10), ` `(25 5, 20 15, 30 30, 25 5)` `)` |

Basically, as we see, the structure translates into a parameter for defining the type of geometry followed by the coordinates of the necessary points that define it in the space in parentheses.

Coordinates are defined by pairs of X and Y separated by spaces, and each pair of coordinates separated by commas.

In the case of elements with multipart geometry, each of the parts in parentheses is separated by a comma, encompassed within a higher order parenthesis that logically must be respected at the beginning and end.

## Load CSV in WKT format in QGIS

For **load data in WKT format in QGIS** From a text file containing a field with such geographic information, we should go to the Layer menu > Data source manager > Delimited text.

In the panel, as if it were a CSV, we must specify the file reading parameters: field delimiters, encoding, field types, coordinate system…

### How can you read a WKT in QGIS

However, in the definition of geometries we must specify that it is a WKT, as well as the type of geometry if it is homogeneous throughout the file. In the sample data viewer we can see the appearance of our data after import.

### How can you read a WKT in QGIS

Once the definition of these parameters is finished, our data should be displayed on the canvas of **QGIS** and appear as a ( layer not as a ) table in the side table of contents. In this case we have loaded a series of lines ( LINESTRING ) that represent the bike lanes of the city of Barcelona.

## Export data in WKT format from QGIS

If we want to obtain the geometric definition of the elements of a layer based on its geometry, we can export any layer in CSV format and specify the desired parameters for saving.

For **export our layer** keeping the field of **geometry in WKT format** We should treat it like a CSV. We will right-click on the > Export > layer Save objects as.

We must specify the file save path and its name, the coordinate reference system, the fields to export and, in the section “ Layer options ”, **define geometry as “ AS_WKT ”** and the type of separator between fields.

### How can you read a WKT in QGIS

## How can you read a WKT in QGIS and use it as a layer of geographic information

By doing this action, we are basically adding a new one **column called “ WKT ”** on our exported layer that contains the geometry in said format, that is, in the POINT ( X Y ) style.

Alternatively, if we wanted to calculate that column without having to export the data to get the geometries in WKT, we could create a new field and calculate that value in it.

The field, obviously, must be of type text and have a sufficient length to house the definition of all geometries. If we assign an extension of the string too short we would get invalid geometries.

The more complex the geometries ( the greater the number of vertices ) the longer their definition will occupy in WKT.

### How can you read a WKT in QGIS

For the **geometry calculation in WKT** in this new field, from the field calculator we must enter the following **formula **from **QGIS**:

1 | `campoWKT = geom_to_wkt($geometry)` |

which basically returns the **geometry in WKT** based on the $ geometry parameter of each element of the layer. In this way, each geometric element is assigned its respective point in WKT with its coordinate pair.