Though looking at an image can be powerful in and of itself, relating imagery to distinct points and shapes adds extra layers of relational analysis.
Projects support the use of annotations as an implementation of these specifically located attributes.
Rasters and Vectors
Geospatial data is generally presented in one of two formats: raster data, which involves an image with individual pixels that are encoded with data continuously over the area of interest, and vector data, which uses sets of points, polygons, and the relationship between them to represent discrete pieces of data.
Rasters include any imagery, but also might be used with a map showing how close any given pixel is to a specific phenomenon, or even showing temperature or likelihood throughout the area represented.
Vectors include points, lines, and polygons, which might represent individual phenomena, roads, buildings, political boundaries, or similar. Each object in vector data has its own metadata, such as a name or population.
Rasters are presented at a specific resolution based on the properties of each pixel, and each pixel has its own data associated with it. (Read more about different types of resolution in What imagery is available?) Vector data does not have resolution, and will appear the same regardless of how zoomed in you are.
Vector data can be used with raster data in many ways: you can use a point or polygon to label specific objects you see in imagery, digitize a map using vectors, or even sample raster data based on a vector object. However, data associated with a vector can be confusing, since there is no distinction of where within the object the data was collected from.
Vector data is represented by annotations within projects. Annotations only include points and polygons, not lines.
You can create annotations on any project and name each polygon or point. In any project, click the
Annotations tab near the top.
Select one of the options from the box on the map, rectangle, polygon, or point. Click on the point where you want to create the annotation, and drag if you are creating a rectangle or polygon.
You can copy the label name and description for multiple annotations by clicking
Bulk create and creating new polygons or points. You can edit annotations and delete them using the appropriate buttons.
At any point, click
Hotkeys or press
? ) to toggle a menu of keyboard shortcuts to create, copy, and move annotations.
If you want to be able to use the annotations you made in another applications, such as QGIS, you will need to export the vector shapes.
You can either export as a Shapefile (useful in QGIS, ArcGIS, and most other GIS applications), or as a GeoJSON, which is useful in web applications and even uploadable to OpenStreetMap.
Export in the Annotations menu, select your format, and click
Export . Your download should begin immediately as a zipped file.
If you want to import vectors--for example, if you want to compare a set of sample points to historical imagery--you can upload a zipped Shapefile or a GeoJSON.
Import in the Annotations menu, click either
Upload GeoJSON or
Upload Zipped Shapefile and select your file. After some time of ingesting, the annotations will appear in your project.